Main findings
In this cross-sectional cohort study, we found that i) maternal fever,
fetal and maternal tachycardia, elevated leukocyte count and CRP were
common findings in term deliveries complicated with chorioamnionitis,
ii) the prevalence of neonatal complications was high, iii) elevated
inflammatory laboratory values, and positive cervical culture were
associated with an increased risk of neonatal infection, and iv)
elevated inflammatory laboratory values, and fetal tachycardia were
associated with an increased risk of asphyxia-related complications. Our
findings highlight the importance of acknowledging signs of
chorioamnionitis, and stresses the need of research focusing on
identifying better predictors and preventive measurements for perinatal
complications in chorioamnionitis at term gestation.
The chorioamnionitis prevalence of 0.47% in our study is considerably
lower compared to previously reported rates of between 1 and 5%.
However, these previously reported rates are, in general, based on older
studies of placental findings of primiparous women, and are consequently
not readily comparable with our results (15). Maternal fever is the most
important clinical sign of chorioamnionitis, and was present in
approximately 90% of the study participants. Surprisingly, maternal
fever was not noted in remaining 10%, which may be a consequence of
inadequate medical chart documentation rather than absence of elevated
maternal temperature. Maternal and fetal tachycardia was highly
prevalent (65% and 67% respectively), which is consistent with
previously reported rates between 50 and 80% (16, 17). Likewise, in
line with previous reports, the presence of subjective clinical signs,
such as uterine tenderness and foul-smelling amniotic fluid, were rare
(17). Uterine tenderness was only noted in 2% of the women with
chorioamnionitis, but can be difficult to determine during active labor
and the presence was only recognized if explicitly stated in the medical
chart text. Hence, the prevalence of these highly subjective clinical
signs is presumably underestimated.
Importantly, according to current guidelines chorioamnionitis diagnosis
can only be confirmed postpartum by histopathological analysis of
placenta and/or positive cervical culture (2). Therefore, we must rely
on clinical signs and laboratory markers of infection when diagnosing
and managing patients with suspected chorioamnionitis in clinical
practice. Suspected chorioamnionitis should imply initiating treatment
with broad-spectrum intravenous antibiotics, careful monitoring and
labor progression should be ensured (2). Although standard obstetric
indications for cesarean delivery apply in deliveries complicated by
chorioamnionitis, the myometrial contractility can be affected by the
inflammation, leading to an increased risk of labor dystocia, cesarean
deliveries and postpartum hemorrhage (18, 19), which presumably explains
the observed high cesarean delivery and postpartum hemorrhage rate in
our study.
Chorioamnionitis is an established risk factor for early- and late-onset
neonatal sepsis (10), and its presence motivates intensified monitoring,
testing, and sometimes empiric antibiotic treatment of the neonate.
Multiple attempts to develop prediction models of the risk of developing
neonatal sepsis have been made, not the least in order to reduce the
usage of empiric antibiotic treatment, which has been associated with an
increased risk of negative childhood outcomes, including asthma (20).
The impact of clinical and laboratory characteristics of
chorioamnionitis on the risk of neonatal complications has not been
addressed in detail previously. We found that a moderately elevated
first leukocyte count, highest maximum CRP level, and positive cervical
culture were associated with neonatal infection, and that high maximum
CRP and fetal tachycardia were associated with asphyxia-related
complications, which is partly a novel finding. Fetal tachycardia in the
presence of maternal fever is a known predictor of adverse neonatal
outcomes, and may be a sign of fetal inflammatory response, which has
been proposed as a mechanism of impaired short- and long-term
neurological outcomes (21, 22). A release of fetal pro-inflammatory
cytokines, in response to inflammation, has been hypostasized to have a
direct toxic effect on the brain leading to adverse neurological
outcomes (12).
A culture was sent in only 70% of cases and of these, only 40% were
positive. However, during the medical chart review it was noted that a
majority of patients were treated with intravenous antibiotics prior to
the culture being taken, which could distort bacterial growth and lead
to false negative cultures. Additionally, there is emerging evidence of
chorioamnionitis being a clinical syndrome with various etiologies,
whereof intra-amniotic infection is one, and sterile intra-amniotic
inflammation is another (23). In fact, similar with our result, previous
studies report low rates of bacteria isolated from cervical or amniotic
fluid cultures in patients with chorioamnionitis (24, 25).