Authors’ Contribution:
Yu Han:Statistical analysis and manuscript writing
Wang Na:Data collection
Wang Chao:Data Collection
Hailan Yang:Project development and final manuscript editing
Analysis of risk factors for cervical insufficiency: a retrospective
controlled study
Introduction
Cervical insufficiency (CI) is one
of the main obstetrical diseases leading to preterm birth, which also
afflicts 4% of patients with recurrent miscarriage.1CI refers to the abnormal remodeling, premature softening and shortening
of the cervix, which is one of the major obstetric disorders leading to
preterm birth and recurrent miscarriage in the second trimester, with an
incidence of 1%-2% that is increasing.2 There are
known risk factors for CI, such as acquired factors including dilatation
and evacuation, dilatation and curettage, induced abortion, previous
cervical laceration, LEEP surgery, cold-knife cone biopsy, or other
cervical surgeries. Congenital factors include utero diethylstilbestrol
exposure, collagen vascular disease, or Müllerian
abnormalities.3
The Canadian Society of Obstetrics and Gynecology (SOGC) clinical
guidelines state that polycystic ovary syndrome (PCOS) is an independent
risk factor for CI.4 In addition, it has been shown
that higher BMI is an independent risk factor for CI;5however, it has also been shown that obese patients have a lower risk of
CI and premature delivery.6 Therefore, whether BMI is
significantly different between CI patients and non-CI patients requires
further elucidation. The Royal College of Obstetricians and
Gynecologists (RCOG) clinical guidelines also consider multiple
pregnancies a risk factor for CI.7 However, whether a
previous history of multiple pregnancies is associated with the
development of CI has not been shown. Additionally, previous studies
have proposed that assisted reproductive technology (ART) is associated
with the occurrence of CI.8 In recent years, though
studies have gradually found that the incidence of CI in the ART
population is high,9 whether ART serves as a risk
factor for CI has not been clarified. Studies have shown that PCOS,
impaired glucose tolerance and type II diabetes, and elevated BMI
together constitute 70% of patients with recurrent
miscarriage.1 At the same time, in our previous study,
it was found that more than 40% of CI patients had gestational diabetes
mellitus (GDM) and pregnancy with diabetes mellitus
(PGDM).10 However, no relevant studies on whether the
incidence of GDM and PGDM is
different in CI patients versus non-CI patients, as well as whether
diabetes can be used as a risk factor to predict the incidence of CI,
currently exist.
In this paper, a single-center retrospective cohort study is conducted
pertaining to the unspecified risk factors of CI by performing
comparisons between the CI population and non-CI population, which may
offer significant insight into the comprehensive management of CI
patients during pregnancy and may clarify further research directions.
Methods
A total of 209 patients with a
singleton pregnancy complicated by CI (CI group) hospitalized in the
First Hospital of Shanxi Medical University from July 2013 to June 2020
were enrolled in this study. The control group (non-CI group) was
randomly selected at a ratio of 1:2 and the inclusion criteria were:
singleton pregnancy and non-cervical insufficiency.
All patients were required to have
records of the whole pregnancy. A total of 348 patients in the control
group who met the criteria were collected. The general conditions,
pregnancy complications (subclinical hypothyroidism, GDM and PGDM, PCOS,
uterine malformation, uterine fibroids/adenomyoma, hypertensive
disorders in pregnancy, anemia, vaginitis, and hyperlipidemia) of the
two groups were then collected. A model of logistic regression was used
to calculate the prediction probability, produce a combination of
multiple indicators of new variables, draw ROC curves, and assess the
predictive ability of risk factors for CI.
Statistical tools, such as Excel and SPSS 20, were used for data entry
and analysis, while the quantitative data were analyzed by the t-test or
analysis of variance and rank sum test. Qualitative data were analyzed
using the chi-square test to
explore the relationship between the variables, while logistic
regression and ROC curves were used for multivariate analysis. α=0.05
was set as the test level.
Results
Comparison in the general conditions between women with CI and
those without CI
As shown in Table 1 ,
there was no statistical difference in age (30.66 ± 3.66 VS 30.28 ±
4.56, P=0.284) and height (1.61 ± 0.05 VS 1.62 ± 0.06, P=0.058) between
CI group and non-CI group.
Compared with the non-CI group,
patients in the CI group had a greater mean body weight (62.49±9.90 VS
58.83±9.17kg, P<0.001), a greater mean BMI (24.20±3.57 VS
22.63±3.63 kg/m2, P<0.001), and a greater
proportion had a BMI of 24 kg/m2 or higher
(50.25%,102/203 VS 29.85%,103/345, P<0.001). Compared with
the non-CI group, the CI group had less mean weight gain during
pregnancy (10.66±6.11 VS 13.36±5.35kg, P<0.001), and there was
no significant difference in the mean BMI at delivery (27.96±3.76 VS
27.77±4.34kg/m2, P=0.602) and in the proportion of
patients with BMI greater than 24 kg/m2 at delivery
between the two groups (88.41%,183/207 VS 84.30%,290/344, P=0.051).
There was no significant difference in the gravidity(2.92±1.20 VS
2.14±1.18, P=1.903), uterine cavity procedures(0.45±0.87 VS 0.50±0.84,
P=0.556), or medical abortions (0.09±0.36 VS 0.05±0.26, P=0.154)between
patients in the CI and non-CI groups. Patients in the CI group had
significantly fewer deliveries(0.26±0.54 VS 0.48±0.59,
P<0.001)and more premature deliveries(0.16±0.40 VS 0.01±0.12,
P<0.001)and spontaneous abortions (1.19±0.93 VS 0.10±0.39,
P<0.001)than those in the non-CI
group. The proportion of patients
in the CI group who had a history of previous multiple pregnancies was
significantly more than that in the non-CI group (7.66%,16/209 VS
0.29%,1/348, P<0.001), while the proportion of patients who
conceived by ovulation induction/IVF-ET was also significantly higher in
the CI group than in the non-CI group (23.44%,49/209 VS 4.89%,17/348,
P<0.001).
2. Comparison in the comorbidities between women with
CI and those without CI
As seen in Table 2 , in the CI group, the incidence of GDM/PGDM
was found to be significantly higher than that in non-CI group
(41.21%,82/199 VS 18.39%,64/348, P<0.001), while patients
with PCOS accounted for a higher proportion in the CI group
(10.55%,21/199 VS 0.86%,3/348, P<0.001). There were no
significant differences in the incidence of subclinical hypothyroidism,
uterine malformations, uterine fibroids/adenomyomas, hypertensive
disorders in pregnancy, anemia, vaginitis, and hyperlipidemia between
the CI group and non-CI group. According to Figure 1 , the
distribution of various complications in the two groups of patients can
be more clearly understood (the results marked with ★★★ are
statistically significant).