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\begin{document}

\title{Association between elevated intrauterine resting tone during labor and
neonatal morbidity: A secondary analysis of a prospective cohort study}



\author[1]{Rebecca Rimsza}%
\author[2]{Nandini  Raghuraman}%
\author[1]{Ebony Carter}%
\author[1]{Jeannie Kelly }%
\author[3]{Alison Cahill}%
\author[4]{Antonina  Frolova}%
\affil[1]{Washington University School of Medicine in Saint Louis}%
\affil[2]{Washington University in Saint Louis School of Medicine}%
\affil[3]{University of Texas at Austin Dell Seton Medical Center}%
\affil[4]{Washington University in Saint Louis}%


\vspace{-1em}



  
  \date{May 27, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
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\selectlanguage{english}
\begin{abstract}
Objective: Internal contraction monitoring during the course of labor
may identify elevated intrauterine resting tone. Our objective was to
assess the association between elevated resting tone during labor and
neonatal morbidity. Design: Secondary analysis of a prospective cohort
study. Setting and Population: Term singleton patients with ruptured
membranes and an intrauterine pressure catheter in place: Tertiary care
hospital, United States of America Methods. Intrauterine resting tone
was calculated as the average baseline pressure between contractions.
The study group had elevated intrauterine resting tone, defined as
intrauterine resting tone [?]75th percentile. Main Outcome Measures:
Composite neonatal morbidity: hypoxic ischemic encephalopathy,
hypothermia treatment, intubation, seizures, umbilical arterial pH [?]
7.1, oxygen requirement, or death. Results: Of the 8580 patient in the
cohort, 2210 (25.8\%) were included. The median intrauterine resting
tone was 9.7 mmHg (IQR 7.3-12.3 mmHg). Elevated resting tone was
associated with shorter median duration of the first stage of labor
(10.0 hrs vs 11.0 hrs, p \textless{}0.01) and lower rates of labor
induction (p \textless{} 0.01). Neonatal composite morbidity was higher
among patients with elevated intrauterine resting tone (5.1\% vs 2.9\%,
p=0.01). After adjusting for chorioamnionitis and amnioinfusion,
elevated intrauterine resting tone was associated with increased risk of
neonatal morbidity (aOR 1.70, 95\% CI 1.06-2.74). Compared to normal
tone, elevated intrauterine resting tone was associated with mild
acidemia and elevated lactate (aOR 1.81, 95\% CI 1.38-2.37 and aOR 1.45,
95\% CI 1.17-1.80, respectively). Conclusion: Elevated intrauterine
resting tone is associated with increased risk of neonatal composite
morbidity. Funding: None%
\end{abstract}%



\sloppy


Title: Association between elevated intrauterine resting tone during
labor and neonatal morbidity: A secondary analysis of a prospective
cohort study

\emph{Author List and Affiliations}

Rebecca R RIMSZA, MD\textsuperscript{1}

Nandini RAGHURAMAN, MD, MSCI\textsuperscript{1}

Ebony B CARTER, MD, MPH\textsuperscript{1}

Jeannie C KELLY, MD\textsuperscript{1}

Alison G CAHILL, MD, MSCI\textsuperscript{2}

Antonina I FROLOVA, MD, PhD\textsuperscript{1}

\textsuperscript{1}Washington University in Saint Louis, Department of
Obstetrics and Gynecology, Division of Maternal-Fetal Medicine and
Ultrasound

660 S. Euclid Ave, Box 8064

St. Louis, MO 63110, USA

\textsuperscript{2}University of Texas at Austin, Dell School of
Medicine, Department of Obstetrics and Gynecology, Division of
Maternal-Fetal Medicine

911 W. 38th Street, Suite 205 Austin, TX 78705, USA

\emph{Corresponding Author Contact Information:}

Rebecca Rimsza, MD

Department of Obstetrics and Gynecology, Washington University School of
Medicine

660 S. Euclid Ave, Box 8064, St. Louis, MO 63110.

e-mail: rimsza@wustl.edu phone: 520-981-0933

Short Title: Intrauterine resting tone and neonatal outcomes

Title: Association between elevated intrauterine resting tone during
labor and neonatal morbidity: A secondary analysis of a prospective
cohort study

\textbf{Abstract}

\textbf{Objective:} Internal contraction monitoring during the course of
labor may identify elevated intrauterine resting tone. Our objective was
to assess the association between elevated resting tone during labor and
neonatal morbidity.

\textbf{Design:} Secondary analysis of a prospective cohort study.

\textbf{Setting and Population:} Term singleton patients with ruptured
membranes and an intrauterine pressure catheter in place: Tertiary care
hospital, United States of America

\textbf{Methods} . Intrauterine resting tone was calculated as the
average baseline pressure between contractions. The study group had
elevated intrauterine resting tone, defined as intrauterine resting tone
[?]75\textsuperscript{th} percentile.

\textbf{Main Outcome Measures:} Composite neonatal morbidity: hypoxic
ischemic encephalopathy, hypothermia treatment, intubation, seizures,
umbilical arterial pH [?] 7.1, oxygen requirement, or death.

\textbf{Results:} Of the 8580 patient in the cohort, 2210 (25.8\%) were
included. The median intrauterine resting tone was 9.7 mmHg (IQR
7.3-12.3 mmHg). Elevated resting tone was associated with shorter median
duration of the first stage of labor (10.0 hrs vs 11.0 hrs, p
\textless{}0.01) and lower rates of labor induction (p \textless{}
0.01). Neonatal composite morbidity was higher among patients with
elevated intrauterine resting tone (5.1\% vs 2.9\%, p=0.01). After
adjusting for chorioamnionitis and amnioinfusion, elevated intrauterine
resting tone was associated with increased risk of neonatal morbidity
(aOR 1.70, 95\% CI 1.06-2.74). Compared to normal tone, elevated
intrauterine resting tone was associated with mild acidemia and elevated
lactate (aOR 1.81, 95\% CI 1.38-2.37 and aOR 1.45, 95\% CI 1.17-1.80,
respectively).

\textbf{Conclusion} : Elevated intrauterine resting tone is associated
with increased risk of neonatal composite morbidity.

\textbf{Funding:} None

\textbf{Keywords:} Labor, Neonatal Outcomes, Intrauterine pressure,
Intrauterine tone, Baseline tone

Tweetable Abstract

Elevated intrauterine resting tone is during labor associated with
increased risk of neonatal morbidity

\textbf{Introduction}

Contraction monitoring during labor is critical to assessing the
clinical response to labor induction. Evaluating uterine response to
oxytocin allows for safe titration to achieve cervical dilation. There
are three main strategies for contraction monitoring: manual palpation,
external tocodynamometry and intrauterine pressure catheter (IUPC).
Manual palpation can vary based on provider experience and maternal body
habitus. An external tocometer allows for monitoring of contraction
frequency and is non-invasive but does not provide an assessment of
contraction magnitude which may be critical when determining need for
cesarean delivery due to failure to progress. Internal contraction
monitoring using an IUPC is more invasive and requires rupture of
membranes prior to use. However, an IUPC offers additional advantages
over tocodynamometry, most importantly, an objective measurement of
intrauterine baseline and contraction-induced pressure, allowing for a
more quantitative assessment of uterine contractility.

Prior to placement, the IUPC is calibrated outside the uterus, with
external atmospheric pressure set as baseline or zero. Once placed
inside the uterus, the IUPC will report a baseline pressure within the
uterus between contractions (resting tone) and a peak intrauterine
pressure when the uterus is maximally contracted. The difference between
these two values calculated over a ten-minute period is considered the
contraction pressure and is measured in Montevideo units (MVU){[}1{]}.
Prior research has focused on the impact of maximum tone and MVUs on
labor duration and cervical dilation {[}2-4{]}. The potential neonatal
effects of elevated baseline intrauterine pressure are unknown, but
prior studies have shown that uterine contractions compress the spiral
arteries, resulting in placental and fetal hypoxia {[}5, 6{]}. We
hypothesized that elevated intrauterine resting tone could lead to
compression of the spiral arteries, thus limiting uterine blood flow and
resulting in neonatal compromise. Therefore, our objective was to assess
the association between elevated resting tone during labor and neonatal
morbidity.

\textbf{Methods}

This was a secondary analysis of a prospective cohort study of singleton
term deliveries from 2010-2014. Patients were included in the analysis
if they were [?]37 weeks gestation, had ruptured membranes and an IUPC in
place for at least 30 minutes prior to delivery. Individual clinician
decision making determined which patients received an IUPC for
contraction monitoring. The patients were not involved in the study
design. The Institutional Review Board and Human Research Protection
Office approved this study. Patients with multiple gestations and those
presenting for scheduled cesarean delivery were excluded. Trained
obstetric research nurses blinded to outcomes abstracted intrauterine
pressure measurements in 10 minute segments. Intrauterine resting tone
was defined as the average baseline pressure between contractions during
the 30 minutes prior to delivery. Elevated intrauterine resting tone was
defined as intrauterine resting tone [?]75\textsuperscript{th} percentile
within this cohort. No established cut offs for defining elevated
intrauterine resting tone have been published therefore the upper
quartile was chosen.

The primary outcome was composite neonatal morbidity which included:
Hypoxic ischemic encephalopathy, hypothermia treatment, intubation,
seizures, umbilical arterial (UA) pH [?] 7.1, neonatal respiratory
support, and neonatal death. Secondary outcomes included lactate [?] 4
mmol/l, NICU admission, 5 min Apgar \textless{}7 and mild acidemia
defined as UA pH \textless{}7.2.{[}7, 8{]}. Mild acidemia was defined as
UA pH \textless{} 7.2 as it has been associated with increased neonatal
morbidity compared to neonates with UA pH [?] 7.2{[}7{]}. Our institution
performs universal umbilical artery cord gases. These outcomes were
compared between patients with and without elevated intrauterine resting
tone.

Baseline demographics and outcomes were compared using\emph{X}
\textsuperscript{2} for categorical variables and the student\emph{t}
test or Mann-Whitney U test for continuous variables, as appropriate.
Normality was tested using the Shapiro-Francia test. Multivariable
logistic regression was used to estimate odds ratios (OR) while
adjusting for potential confounders. Initial confounders included in the
models were selected based on the results of univariate analyses and
those that had biologic plausibility {[}9-13{]} {[}14{]}. Initial models
included obesity, amnioinfusion, tachysystole, induction, parity and
fetal growth restriction. A backwards step-wise selection was then
performed, keeping only covariates that remained significant (P
\textless{} 0.1). Regression models assessing the association between
neonatal outcomes and elevated intrauterine resting tone included
amnioinfusion as this has been previously associated with changes in
uterine tone and neonatal outcomes, however, this covariate was not
significant in the final model {[}13, 15{]}. Model fit was confirmed
with the Hosmer-Lemeshow goodness of fit test{[}16{]}.

A sub-group analysis was performed to evaluate the association between
persistent elevated intrauterine pressure and primary and secondary
outcomes. Persistent elevated intrauterine pressure was defined as
present at both 30 and 120 min prior to delivery. Multivariable
regression models were used to estimate the OR for primary and secondary
outcomes for patients with normal uterine pressure, elevated resting
tone only for the last 30 minutes prior to delivery and for patients
with persistently elevated intrauterine pressure were performed. To
account for elevated tone related to tachysystole, we performed an
additional sensitivity analysis excluding those with uterine
tachysystole during the monitoring period. We also performed a
sensitivity analysis of patients who had elevated resting intrauterine
pressure only in the second stage of labor.

All patients meeting inclusion criteria were included and an \emph{a
priori} sample size estimation was not performed. STATA Version 16
(STATA Corp., College Station, TX) was used to perform all analyses.
STROBE guidelines were followed throughout the study {[}17{]}.

\textbf{Results}

Of the 8580 patients in the cohort, 2210 (25.8\%) had an IUPC with at
least 30 minutes of pressure data prior to delivery and were included in
this analysis. The median intrauterine resting tone was 9.7 mmHg (IQR
7.3-12.3 mmHg; Figure 1). A total of 567 patients had an average
elevated resting intrauterine tone [?] 12.3 mmHg ([?]75\textsuperscript{th}
percentile).

Admission body mass index was higher for patients with elevated resting
tone (33 mmHg {[}IQR 29-39{]} vs 32 mmHg {[}28-38{]}, p \textless{}
0.01.) Patients with elevated resting tone were also older and more
likely to be nulliparous (Table 1). Incidence of maternal comorbidities
including chronic hypertension, pregnancy associated hypertension, and
pregestational diabetes were not significantly different between groups
(p \textless{} 0.05). Neonatal birth weight and incidence of
intrauterine growth restriction did not differ for patients with
elevated resting tone (Table 1).

Patients with elevated resting tone were less likely to undergo
induction of labor (52.9 vs 60.4\%, p\textless{}0.05) and were less
likely to deliver by cesarean (0.4\% vs 2.4\%, p\textless{} 0.05).
Oxytocin use (84.0 vs 89.9\%, p\textless{}0.01) and maximum oxytocin
dose achieved (12 mu/min {[}IQR 6-18{]} vs 14 mu/min {[}8-20{]},
p\textless{}0.01) were lower for patients with elevated resting tone
compared to those with normal resting tone. Chorioamnionitis was more
common among patients with high resting tone (6.2\% vs 3.7\%, p = 0.01).
While the median durations of 1\textsuperscript{st} and
2\textsuperscript{nd} stage of labor differed slightly between patients
with elevated and normal resting tone, overall prolonged labor duration
\textgreater{} 24hrs and prolonged 2\textsuperscript{nd} stage [?] 3hrs
were similar (Table 2). Incidence of tachysystole is more common for
patients with elevated resting tone then patients with normal tone
(15.3\% vs 1.3\%, p\textless{}0.01).

Composite neonatal morbidity was significantly higher in the group with
elevated resting tone (5.1\% vs 2.9\%, p = 0.01; Table 3). After
adjusting for amnioinfusion and chorioamnionitis, elevated intrauterine
resting tone was associated with increased odds of neonatal morbidity
(aOR 1.70 95\% {[}CI 1.06-2.74{]}; Table 3). Elevated intrauterine
resting tone was associated with mild acidemia and elevated lactate (aOR
1.81 {[}95\%CI 1.38-2.37{]} and aOR 1.45 {[}95\% CI 1.17-1.80{]}
respectively; Table 3). The incidence of low Apgar score at 5 minute and
NICU admission was similar between groups (Table 3). Among women without
evidence of tachysystole, high intrauterine resting tone remained
significantly associated with increased risk of neonatal composite
morbidity (aOR 1.64 {[}95\%CI 1.01-2.78{]}).

A sub-group analysis stratified patients with intrauterine pressure for
30 minutes and 120 minutes prior to delivery. Persistently elevated
intrauterine tone for 120 minutes prior to delivery was seen in 234
patients, representing 41\% of all patients with elevated intrauterine
resting tone. Increasing duration of elevated resting tone was
associated with increased risk of composite neonatal morbidity (2.9\%
for normal resting tone vs 3.9\% for 30 minutes elevated resting tone vs
6.8\% for 120 minutes elevated resting tone; p for trend 0.03). After
adjusting for amnioinfusion and chorioamnionitis, persistently elevated
intrauterine tone was associated with increased risk of neonatal
morbidity while elevated tone for only 30 minutes did not (aOR
2.21{[}95\% CI 1.22-4.01{]} and aOR 1.34 {[}95\% CI 0.71-2.50{]},
respectively). A similar pattern was noted for lactate [?] 4 mmol/l,
5-minute Apgar score \textless{} 7, and umbilical artery pH \textless{}
7.2 (Table 4). The majority of patients included in the analysis were in
the second stage of labor (98.1\%). In a sensitivity analysis excluding
those who delivered in the first stage of labor, elevated intrauterine
resting tone remained significantly associated with composite neonatal
morbidity (aOR 1.77 {[}95\% CI 1.09-2.86{]}).

\textbf{Discussion}

\emph{Main Findings}

Our findings indicate that higher intrauterine resting tone is
associated with a significantly increased risk of composite neonatal
morbidity, and evidence of neonatal acidemia with higher incidence of
umbilical arterial pH \textless{} 7.2 and a lactate \textgreater{} 4
mmol/l. Additionally, increasing duration of elevated resting tone was
associated with increased risk of composite neonatal morbidity

\emph{Strengths and Limitations}

Strengths of this study include use of a large diverse cohort, allowing
for subgroup analysis and larger generalization of the results.
Assessment of resting intrauterine tone is novel and addresses a
quandary that is identified in clinical practice. There are several
limitations to this study. First, placement of IUPC at our institution
is not universal and thus the cohort is subject to selection bias.
Additionally, our database only included the last 120 minutes of IUPC
data, limiting our analysis to this timepoint. Due to a paucity of data
on the average or ``normal'' resting intrauterine tone there is no
established definition of elevated tone. We chose [?] 75\%, however,
further investigations with larger sample sizes should be used to
determine a possible threshold resting tone that is associated with
uterine hypoperfusion and neonatal morbidity The majority of patients
delivered vaginally and were primarily in the second stage of labor for
the duration of available IUPC data. Thus, we were unable to assess the
effects of elevated resting tone throughout the first stage of labor.
Lastly, while the number of patients included in the study was sizable
it remains underpowered for individual analysis of rare adverse events
leading to the need for a composite outcome with the potential bias
associated with pooling outcomes.

\emph{Interpretation}

Numerous studies have shown that uterine contractions result in
compression of the uterine spiral arteries, decreased placental
perfusion and intermittent fetal hypoxia {[}5, 18-21{]}. Peebles et al.
additionally indicated that an interval of 2-3 minutes between
contractions resulted in stable fetal cerebral hemoglobin saturations,
while shorter intervals resulted in decreased
oxyhemoglobin:deoxyhemoglobin ratios {[}22{]}. Thus, the time between
contractions allows for maternal-fetal gas exchange, fetal metabolic
recovery, and maintenance of normal fetal acid base status. In cases of
uterine tachysystole, when this recovery time is decreased, accumulation
of cord blood lactate is seen {[}23{]}. Our data suggest that higher
intrauterine pressure during this recovery phase is associated with
increased risk of fetal acidemia (as evidenced by low pH and elevated
lactate in the umbilical artery). We suspect that the increased uterine
resting tone results in decreased recovery in utero-placental perfusion
between contractions, similar to the effect seen with tachysystole. In
our sub-group analysis, excluding women with evidence of tachysystole
prior to delivery, we observed the same relationship between
intrauterine resting tone and neonatal morbidity, suggesting an
independent effect.

\emph{Conclusion}

\emph{Clinical Implications and practical recommendations}

Elevated baseline intrauterine tone noted during labor prompts questions
regarding subsequent labor management. Our data show that elevated
intrauterine resting tone is associated with neonatal compromise. We
propose that this be considered during management of labor close to
delivery. While the impact of this finding is not robust enough for us
to suggest immediate or emergent delivery due to fetal concerns, the
study should be used to interpret IUPC data in the context of labor
progress, duration, and fetal tolerance.

Elevated intrauterine tone among patients in the second stage provides a
context for potential intervention. Oxytocin augmentation is commonly
continued from the first stage of labor into the second stage, however,
it remains unclear if additional increased expulsion ``power'' is
necessary to effect vaginal delivery following complete dilation.
Oxytocin has known risks including fetal acidemia especially when used
during the second stage {[}24{]}. Vlachos et al investigated the impact
of stopping oxytocin infusions once active labor has been achieved and
found that less cases of non-reassuring fetal heart rates were observed
{[}25{]}. However, literature specifically evaluating need for oxytocin
during the second stage is needed to determine the potential safety of
continuing a common obstetrical practice. Similarly, we were unable to
assess effects of elevated resting tone specifically during the first
stage and cannot make conclusions regarding effects on neonatal
morbidity outside the context of second stage of labor.

Incidence of lower umbilical cord pH has been associated with longer
second stage. A meta-analysis from 2020 found a RR 2.00 (95\% CI
1.30-3.07) {[}26{]}. Our data suggest that longer exposure to elevated
resting tone is also associated with fetal acidemia and may compound the
effects of prolonged second stage. Therefore, practice patterns to
shorten the second stage of labor such as immediate pushing, manual
rotation of occiput posterior position, and traditional coached pushing
may also be employed to reduce time the fetus spends exposed to elevated
pressure {[}27-30{]}.

\emph{Research Implications and recommendations}

Our data are among the first to suggest a link between intrauterine
resting tone during labor and neonatal outcomes. We hypothesize that
this is a result of persistent utero-placental hypoperfusion during
labor due to limited recovery of uterine and spiral artery blood flow
between contractions. However, this hypothesis will need to be tested
with future clinical and mechanistic studies. The most relevant and
urgent research directions to consider are whether duration of elevated
intrauterine resting tone affects neonatal outcomes and to determine a
more precise definition of ``elevated'' resting tone, rather than our
empiric cutoff of \textgreater{}75\textsuperscript{th} percentile.
Additionally, studies examining whether any interventions, such as
positional changes or intermittent pushing during second stage of labor,
can decrease intrauterine resting tone and subsequently fetal morbidity,
are needed.

We found that induction of labor, which applied to 58\% of patients in
the cohort, was less common among women with elevated resting tone.
Similarly, women with elevated resting tone were less likely to receive
oxytocin and had lower maximum doses of oxytocin during their labor.
Despite fewer interventions, women with elevated resting tone were more
likely to have a vaginal delivery. These findings suggest that higher
resting tone may be a surrogate for more efficient uterine contractility
and labor. However, since women in this cohort had an indication for
IUPC placement, most likely due to dysfunctional labor, these findings
need further assessment in a non-biased cohort. Further research is
needed to determine the association between elevated resting tone,
uterine contractility and labor progress.

\emph{Conclusions}

Our findings suggest that elevated intrauterine resting tone is
associated with increased risk of neonatal composite morbidity and may
compound with time. Further investigation is needed to guide management
of patients who experience elevated intrauterine resting tone during
labor.

\par\null

Acknowledgements: none

Disclosure of Interests

The authors report no conflicts of interest

Contribution to authorship

All authors were involved in study conception and design. Dr. Alison
Cahill specifically assisted with acquisition of data and drafting and
revising the manuscript. Dr. Nandini Raghuraman was instrumental in
conception, design, statistical analysis and drafting the manuscript.
Dr. Ebony Carter assisted with acquisition of data and revising
critically important manuscript drafts. Dr. Jeannie Kelly assisted with
data collection and revising of critically important manuscript and
intellectual content. Dr. Antonina Frolova was critical in conception,
analysis and interpretation of data, and revising the manuscript for
critically important intellectual content.

Details of Ethics Approval

The Institutional Review Board and Human Research Protection Office
approved this study. IRB \#202008034. Initial approval on August
6\textsuperscript{th}, 2020 and reapproved on February
19\textsuperscript{th}, 2021.

Funding: None

Figure Caption: Average resting tone in the 30 minutes prior to
delivery.

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uterine blood flow during uterine contractions.} Am J Obstet Gynecol,
1969. \textbf{103} (8): p. 1108-16.

21. Borell, U., et al., \emph{Influence of Uterine Contractions on the
Uteroplacental Blood Flow at Term.} Am J Obstet Gynecol,
1965.\textbf{93} : p. 44-57.

22. Peebles, D.M., et al., \emph{Relation between frequency of uterine
contractions and human fetal cerebral oxygen saturation studied during
labour by near infrared spectroscopy.} Br J Obstet Gynaecol,
1994.\textbf{101} (1): p. 44-8.

23. Palanisamy, A., et al., \emph{Association between Uterine
Tachysystole during the Last Hour of Labor and Cord Blood Lactate in
Parturients at Term Gestation.} Am J Perinatol, 2019. \textbf{36} (11):
p. 1171-1178.

24. Bakker, P.C., et al., \emph{Elevated uterine activity increases the
risk of fetal acidosis at birth.} Am J Obstet Gynecol, 2007.\textbf{196}
(4): p. 313.e1-6.

25. Vlachos, D.E., et al., \emph{Oxytocin discontinuation after the
active phase of labor is established.} J Matern Fetal Neonatal Med,
2015. \textbf{28} (12): p. 1421-7.

26. Di Mascio, D., et al., \emph{Delayed versus immediate pushing in the
second stage of labor in women with neuraxial analgesia: a~systematic
review and meta-analysis of randomized controlled trials.} Am J Obstet
Gynecol, 2020. \textbf{223} (2): p. 189-203.

27. Bloom, S.L., et al., \emph{A randomized trial of coached versus
uncoached maternal pushing during the second stage of labor.} Am J
Obstet Gynecol, 2006. \textbf{194} (1): p. 10-3.

28. Burd, J., et al., \emph{Prophylactic rotation for malposition in the
second stage of labor: a systematic review and meta-analysis of
randomized controlled trials.} Am J Obstet Gynecol MFM, 2021: p. 100554.

29. Masturzo, B., et al., \emph{Sonographic evaluation of the fetal
spine position and success rate of manual rotation of the fetus in
occiput posterior position: A randomized controlled trial.} J Clin
Ultrasound, 2017. \textbf{45} (8): p. 472-476.

30. Cahill, A.G., et al., \emph{Effect of Immediate vs Delayed Pushing
on Rates of Spontaneous Vaginal Delivery Among Nulliparous Women
Receiving Neuraxial Analgesia: A Randomized Clinical Trial.} Jama,
2018.\textbf{320} (14): p. 1444-1454.

Table 1: Maternal demographics and characteristics between patients with
and without elevated intrauterine resting tone

\par\null\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
\begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
Elevated resting tone\textsuperscript{a} N= 567\strut
\end{minipage} & \begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
Normal resting tone N= 1643\strut
\end{minipage} & \begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
p-value\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
Maternal demographics\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Age (y)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
24.3 \selectlanguage{ngerman}± 5.34\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
26.0 \selectlanguage{ngerman}± 5.9\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Advanced maternal age\textsuperscript{b}\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
29 (5.1)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
157 (9.6)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
Race Black White Latina Other\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
422 (75.1) 94 (16.7) 30 (5.3) 16 (2.9)\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
1164 (71.2) 321 (16.7) 101 (6.2) 48 (2.9)\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
0.35\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Body mass index (kg/m\textsuperscript{2})\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
33 (29, 39)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
32 (28, 38)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Maternal weight (kg)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
89.0 (74.5-106.1)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
85.3 (73.5-101.6)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{0.02}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
Pregnancy characteristics\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~~Gestational age (Weeks)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
39.3 \selectlanguage{ngerman}± 1.2\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
39.1 \selectlanguage{ngerman}± 1.3\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{0.04}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Gestational age \textless{}39 weeks\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
218 (38.5)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
706 (43.0)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.06\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Nulliparity\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
87 (50.6)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
622 (37.9)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~~ Prior cesarean delivery\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
51 (9.0)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
166 (10.1)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.44\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
Maternal comorbidities\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~~Chronic hypertension\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
37 (6.5)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
109 (6.6)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.93\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Hypertensive disorder of pregnancy\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
125 (22.1)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
334 (20.3)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.39\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Pregestational diabetes\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
13 (2.3)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
20 (1.2)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.07\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
Fetal Characteristics\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Fetal growth restriction\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
90 (15.9)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
272 (16.6)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.71\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Birthweight (g)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
3165 \selectlanguage{ngerman}± 472\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
3164 \selectlanguage{ngerman}± 471\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.17\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Male sex\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
286 (50.4~)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
817 (49.7)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.77\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Defined as maternal
age [?] 35 at time of delivery *Data presented as N(\%), Mean \selectlanguage{ngerman}± SD, or
Median (IQR)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Defined as maternal
age [?] 35 at time of delivery *Data presented as N(\%), Mean \selectlanguage{ngerman}± SD, or
Median (IQR)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Defined as maternal
age [?] 35 at time of delivery *Data presented as N(\%), Mean \selectlanguage{ngerman}± SD, or
Median (IQR)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Defined as maternal
age [?] 35 at time of delivery *Data presented as N(\%), Mean \selectlanguage{ngerman}± SD, or
Median (IQR)\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{ngerman}

Table 2: Labor characteristics and mode of delivery between patients
with and without elevated intrauterine resting tone\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
\begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
Elevated resting tone\textsuperscript{a} N= 567\strut
\end{minipage} & \begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
Normal resting tone N= 1643\strut
\end{minipage} & \begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
p-value\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
Labor characteristics\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Induction of labor\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
300 (52.9)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
992 (60.4)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Artificial rupture of membranes\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
391 (69.0)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
1,161 (70.7)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.44\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Oxytocin use\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
476 (84.0)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
1475 (89.8)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~~~~~~ Maximum oxytocin dose\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
12 (6-18)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
14 (8-20)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~~~~~~ High dose oxytocin (\textgreater{}20 mu/min)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
100 (21.0)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
395 (25.8)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Prostaglandin use\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
124 (21.9)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
363 (22.1)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.91\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Magnesium use\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
50 (8.8)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
143 (8.7)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.93\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Chorioamnionitis\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
35 (6.2)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
61 (3.7)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Terbutaline\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
25 (4.4)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
85 (5.2)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.47\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Labor Length (hrs)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
12.1 (8.2-16.8)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
12.5 (8.7-18.3)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.07\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~~~~ Duration of 1\textsuperscript{st} stage (hrs)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
10.0 (6.4-15.0)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
11.0 (7.3-16.4)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
~ ~~~Duration of 2\textsuperscript{nd} stage (min)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
29 (16-54)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
26 (13-51)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{0.02}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Labor duration \textgreater{}24hrs\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
57 (10.1)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
182 (11.1)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.51\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Prolonged 2nd stage ([?]3hrs)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
19 (3.4)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
36 (2.2)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
0.15\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Tachysystole in last 30 minutes\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
87 (15.3)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
22 (1.3)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
Mode of delivery Spontaneous vaginal Operative vaginal Cesarean
delivery\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
527 (93.0) 38 (6.7) 2 (0.4)\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
1490 (90.7) 113 (6.9) 40 (2.4)\strut
\end{minipage} & \begin{minipage}[t]{0.24\columnwidth}\raggedright\strut
\textbf{\textless{}0.01}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile *Data presented as N(\%), Mean \selectlanguage{ngerman}± SD,
or Median (IQR)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile *Data presented as N(\%), Mean \selectlanguage{ngerman}± SD,
or Median (IQR)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile *Data presented as N(\%), Mean \selectlanguage{ngerman}± SD,
or Median (IQR)\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile *Data presented as N(\%), Mean \selectlanguage{ngerman}± SD,
or Median (IQR)\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{ngerman}

Table 3: Neonatal outcomes among patients with elevated intrauterine
tone\selectlanguage{english}
\begin{longtable}[]{@{}llllll@{}}
\toprule
\begin{minipage}[b]{0.16\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[b]{0.16\columnwidth}\raggedright\strut
Elevated resting tone\textsuperscript{a} N=567\strut
\end{minipage} & \begin{minipage}[b]{0.16\columnwidth}\raggedright\strut
Normal resting tone N=1643\strut
\end{minipage} & \begin{minipage}[b]{0.16\columnwidth}\raggedright\strut
P value\strut
\end{minipage} & \begin{minipage}[b]{0.16\columnwidth}\raggedright\strut
OR (95\% CI)\strut
\end{minipage} & \begin{minipage}[b]{0.16\columnwidth}\raggedright\strut
aOR (95\% CI)\textsuperscript{b}\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Composite neonatal morbidity\textsuperscript{c}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
29 (5.1)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
48(2.9)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.01\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.79 (1.16-2.87)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.70 (1.06-2.74)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Hypoxic ischemic encephalopathy\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1 (0.2)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1 (0.1)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.43\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Hypothermia treatment\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
2 (0.4)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
3 (0.2)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.46\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Intubation\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
3 (0.5)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
9 (0.6)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.96\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Seizures\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
-\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
3 (0.2)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.31\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Neonatal death\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1 (0.2)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1 (0.1)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.43\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Umbilical artery pH \textless{} 7.1\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
10 (1.8)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
17 (1.0)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.17\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Oxygen therapy\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
15 (2.7)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
30 (1.8)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.23\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
NICU admission\textsuperscript{d}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
9 (1.6)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
14 (0.9)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.14\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.88 (0.81-4.36)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.79 (0.77-4.18)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
5-minute Apgar score \textless{}7\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
16 (2.8)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
26 (1.6)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.06\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.81 (0.96-3.39)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.73 (0.92-3.26)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Umbilical artery\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
pH \textless{}7.2\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
97 (17.1)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
165 (10.2)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textless{}0.01\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.83 (1.39-2.40)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.81 (1.38-2.37)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Lactate [?] 4 mmol/l\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
178 (31.5)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
382 (23.7)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textless{}0.01\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.48 (1.20-1.83)\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.45 (1.17-1.80)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

Table 4: Neonatal outcomes among patients with elevated intrauterine
tone 30 minutes and 120 minutes prior to delivery\selectlanguage{english}
\begin{longtable}[]{@{}lllllll@{}}
\toprule
\begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
Normal resting tone N=1643\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
Elevated\textsuperscript{a} resting tone 30 min prior to delivery
N=333\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
Persistent elevated resting tone 120 min prior to delivery N=234\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
aOR (95\% CI)\textsuperscript{b} Normal vs 30min\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
aOR (95\% CI)\textsuperscript{b} Normal vs 120min\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
P for trend\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Composite neonatal morbidity\textsuperscript{c}\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
48(2.9)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
13 (3.9)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
16 (6.8)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
1.34 (0.71-2.50)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textbf{2.21 (1.22-4.01)}\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
0.03\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
NICU admission\textsuperscript{d}\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
14 (0.9)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
4 (1.2)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
5 (2.1)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
1.39 (0.45-4.26)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
2.33 (0.82-6.62)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
0.28\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
5-minute Apgar Score \textless{}7\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
26 (1.6)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
4 (1.2)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
12 (5.1)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
0.74 (0.26-2.15)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textbf{3.14 (1.55-6.37)}\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textless{}0.01\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Umbilical artery\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
pH \textless{}7.2\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
165 (10.2)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
56 (16.8)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
41 (17.5)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textbf{1.79 (1.29-2.48)}\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textbf{1.84 (1.26-2.67)}\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textless{}0.01\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Lactate [?] 4 mmol/l\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
382 (23.7)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
93 (28.0)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
85 (36.3)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
1.25 (0.96-1.63)\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textbf{1.78 (1.33-2.39)}\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textless{}0.01\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
\textsuperscript{a}Elevated tone defined as \textgreater{}
75\textsuperscript{th} percentile \textsuperscript{b}Adjusted for
chorioamnionitis, amnioinfusion \textsuperscript{c}Composite Neonatal
Morbidity: Hypoxic Ischemic encephalopathy, hypothermia treatment,
intubation, seizures, UA pH[?]7.1, oxygen requirement, and neonatal death
\textsuperscript{d}Neonatal intensive care admission\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
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