†These authors contributed equally.
Academic Editor: Michael H. Dahan
Background: Some models predicting cesarean section (CS) have
been proposed, with Tolcher, Levine, and Burke model well acknowledged. Tolcher
model targets nulliparous women with term labor induction; Levine model targets
women with term labor induction with intact membranes and an unfavorable cervix.
Burke model targets term nulliparous woman with an uncomplicated pregnancy. Our
objective was to assess the predictive performance of these three models, and to
disclose the variables which may predict the risk of CS in Chinese population.
Methods: A retrospective study was conducted on women with singleton,
term, cephalic pregnancies at a tertiary academic center (2011–2017). A
predicted probability for CS was calculated for women in the dataset by the
algorithm of each model. The performance of the model was evaluated for
discrimination. Univariate analysis was used to screen out the factors that may
increase the risk of CS. Results: The three models predicted CS as
following (expressed by an area under the receiver operating characteristic curve
[AUC ROC]) (in the population defined/employed by each model): Tolcher model with
AUC ROC of 0.659; Levine model with 0.697; and Burke model as 0.623. Different
interventional measures or characteristics of labor were also evaluated; the
nulliparous and multiparous were analyzed separately. Still, most of the results
were unsatisfactory (AUC ROC
Cesarean section (CS) is an important surgery within the obstetric domain. It has become an effective means to solve dystocia and some obstetric complications, and to save maternal and perinatal lives. However, it is not a normal mode of delivery. Apart from the risks of the surgical procedure itself, it could also cause short and long term complications [1, 2]. In addition to have a profound impact on childbirth experiences of women, trial of labor has clinical and social implications due to their unpredictable duration and chance of success [3]. On the other hand, the childbirth experience among nulliparous women may affect her next pregnancy, especially with the introduction of China’s universal two-child and three-child policies. Therefore, in order to improve their outcomes, providing the safe, appropriate and personalized delivery mode according to the view of mothers and their babies is vital.
Currently, several published models, which were
based on maternal and fetal variables, were
available to predict the probability of unplanned CS in women at term
[4, 5, 6, 7, 8]. A study by Tolcher et al. [4] used a nomogram to predict
the probability of CS. Tolcher model was developed using a retrospective cohort
of 785 nulliparous undergoing induction of labor at term at Mayo Clinic Rochester
and had a good discriminatory ability with a bias-corrected c-index of 0.709
(95% confidence interval [CI] 0.671–0.750). Levine et al. [5] developed and validated a predictive model for women undergoing an induction of
labor at term with intact membranes and an unfavorable cervix (Bishop score
However, these prediction models’ population is majority white. It is not clear whether these models are applicable to other ethnicity. To date, there is no method to accurately stratify pregnant women according to their risk profile for CS. The benefits of using these models should be demonstrated before routine introduction into clinical practice. Thus, the aim of study was to assess the predictive performance of three foreign models for Chinese population, and to discover the variables which may be useful to predict the risk of CS in this population.
A retrospective study was conducted on women who fulfilled the following inclusion and exclusion criteria at a tertiary care academic center in the department of obstetrics and gynecology of the First Affiliated Hospital of Soochow University from January 1st, 2011 to August 31st, 2017. The protocol for this study was approved by the Institutional Review Board at this center (2018019).
Women with singleton, term (37 0/7 weeks of gestation or greater) and cephalic pregnancies were eligible for inclusion. Women were excluded if they had any one of the following: severe complications during pregnancy (cardiac failure, severe liver and kidney diseases, severe preeclampsia complicated with organ dysfunction), a scared uterus (prior CS delivery or myomectomy), complete or partial placenta previa or vasa previa, prolapse or presentation of umbilical cord, other contraindications to vaginal delivery. Women with the CS on maternal request were also excluded.
The outcome of interest was defined as CS. Data on maternal characteristics and
perinatal parameters were collected from the institution’s obstetrics database,
which was obtained by the patient’s medical record review. The following
variables were recorded (Table 1): maternal parity, age, height, weight, baseline
body mass index (BMI) (BMI was calculated as weight/height
Variable | Cesarean section (n = 725, among nulliparous) | Vaginal delivery (n = 6636, among nulliparous) | p* | Cesarean section (n = 34, among multiparous | Vaginal delivery (n = 2379, among multiparous) | p* | |
Maternal age (y) | 27.58 |
26.90 |
32.44 |
30.57 |
0.006 | ||
Baseline height (cm) | 159.64 |
161.69 |
159.24 |
161.10 |
0.017 | ||
Baseline BMI (kg/m |
21.64 |
20.88 |
23.36 |
21.67 |
|||
Weight change during pregnancy (kg) | 14.59 |
14.05 |
0.001 | 13.38 |
12.86 |
0.488 | |
BMI at delivery (kg/m |
27.37 |
26.26 |
28.63 |
26.63 |
|||
Gestational age at delivery (w) | 40.18 |
39.74 |
40.00 |
39.62 |
0.015 | ||
HDP | 36 (4.97%) | 149 (2.25%) | 1 (2.94%) | 41 (1.72%) | 1.000 | ||
Diabetes mellitus | 0.001 | 0.207 | |||||
None | 665 (91.72%) | 6275 (94.56%) | 29 (85.29%) | 2184 (91.80%) | |||
Pre-existing | 2 (0.28%) | 2 (0.03%) | 0 (0.00%) | 1 (0.04%) | |||
GDM | 58 (8.00%) | 359 (5.41%) | 5 (14.71%) | 194 (8.15%) | |||
ICP | 5 (0.69%) | 23 (0.35%) | 0.190 | 0 (0.00%) | 12 (0.50%) | 1.000 | |
Amniotic fluid volume | 0.015 | ||||||
Normal | 671 (92.55%) | 6512 (98.13%) | 31 (91.18%) | 2338 (98.27%) | |||
Polyhydramnios | 24 (3.31%) | 55 (0.83%) | 1 (2.94%) | 23 (0.97%) | |||
Oligohydramnios | 30 (4.14%) | 69 (1.04%) | 2 (5.88%) | 18 (0.76%) | |||
Uterine myoma | 6 (0.83%) | 25 (0.38%) | 0.139 | 0 (0.00%) | 10 (0.42%) | 1.000 | |
PROM | 175 (24.14%) | 1395 (21.02%) | 0.052 | 6 (17.65%) | 379 (15.93%) | 0.786 | |
Intervention/augmentation methods | |||||||
Non-intervention group plus Augmentation group | 134 (18.48%) | 2811 (42.36%) | 7 (20.59%) | 1242 (52.21%) | |||
Oxytocin Induction group | 173 (23.86%) | 1103 (16.62%) | 6 (17.65%) | 197 (8.28%) | |||
Amniotomy group | 345 (47.59%) | 2438 (36.74%) | 18 (52.94%) | 889 (37.37%) | |||
Disposable Cervical Dilator Balloon group | 30 (4.14%) | 99 (1.49%) | 3 (8.82%) | 42 (1.77%) | |||
Prostaglandin E2 group | 43 (5.93%) | 185 (2.79%) | 0 (0.00%) | 9 (0.38%) | |||
Epidural analgesia | 29 (4.00%) | 179 (2.70%) | 0.044 | 0 (0.00%) | 11 (0.46%) | 1.000 | |
Meconium-stained amniotic fluid | |||||||
0 | 547 (75.45%) | 6109 (92.06%) | 24 (70.59%) | 2162 (90.88%) | |||
I | 42 (5.79%) | 246 (3.71%) | 1 (2.94%) | 94 (3.95%) | |||
II | 38 (5.24%) | 163 (2.46%) | 4 (11.76%) | 61 (2.56%) | |||
III/ bloody | 98 (13.52%) | 118 (1.78%) | 5 (14.71%) | 62 (2.61%) | |||
Male infant | 410 (56.55%) | 3247 (48.93%) | 24 (70.59%) | 1217 (51.16%) | 0.024 | ||
Infant birth weight | 3527.63 |
3341.07 |
3754.41 |
3452.55 |
|||
BMI, body mass index; PROM, premature rupture of membranes; HDP, hypertensive
disorders of pregnancy; ICP, intrahepatic cholestasis of pregnancy; GDM,
gestational diabetes mellitus. Data are mean * Two-sided p based on the |
We searched the literature for models that predicted the likelihood of CS among women with singleton, term, and cephalic pregnancies between January 1st, 2011 to August 31st, 2017, the same period as our study period. Considering the limitations of retrospective data collection, three studies [4, 5, 6] with relatively larger sample sizes were selected for external validation. These original articles were published in first-class obstetrics and gynecology journals and worthy. The detailed parameters of three models (Tolcher, Levine and Burke models) were presented in Supplementary Table 1.
A predicted probability for CS was calculated for woman in the dataset by means of published each model algorithm. The algorithms of the three models all used nomograms to calculate the probability of CS. For a given woman, each characteristic was aligned with the corresponding number of scores on the scores axis in the nomogram, and a total summated score was derived. The sum of all scores lined with predicted probability of CS in the nomogram.
Considering the induction/augmentation methods of labor may affect the delivery mode, we used the following methods for grouping based on the experience of the study institution. Firstly, women were divided into the Non-intervention group and the Intervention group according to whether they received intervention measures. The Non-intervention group was defined as women who entered labor naturally and the labor process did not be intervened. Then, women of the Intervention group were divided into the Augmentation group and Induction group according to whether the initial cervix was dilated by 6 cm. Women who received intervention measures such as amniotomy and/or oxytocin when their initial cervical dilation was greater than or equal to 6 cm were defined as the Augmentation group. Women who received intervention measures when their initial cervical dilation was less than 6 cm were defined as the Induction group. The Induction group was then divided into four subgroups according to different induction methods. (1) Oxytocin Induction group: Women only received oxytocin induction. (2) Amniotomy group: Women received artificial rupture of membranes with or without oxytocin induction. (3) Prostaglandin E2 group: Women received Prostaglandin E2 (Propess) induction. (4) Disposable Cervical Dilator Balloon group: Women received disposable cervical dilator balloon induction.
For continuous variables, the tests of normality was performed first. The
Student’s t-test was used to compare the continuous variables with a normal
distribution. The chi-square test, Fisher exact test and Wilcoxon rank-sum test
were used, as appropriate, for the categorical variables. Standard descriptive
statistics (mean
During the study period, a total of 18,228 deliveries were delivered at the hospital. After exclusion of ineligible patients, 7361 nulliparous and 2413 multiparous women were enrolled. 725 nulliparous and 34 multiparous women underwent CS delivery. Non-reassuring fetal heart rate status was the most common indication for CS (nulliparous: 354/725 = 48.83%; multiparas: 18/34 = 54.94%) followed by arrest of active phase (nulliparous: 153/725 = 21.10%; multiparas: 8/34 = 23.53%).
The chi-square test was performed for maternal parity, and the result
significant difference between the vaginal and cesarean group (p
Maternal and neonatal characteristics were compared between women who underwent CS and women who delivered vaginally (Table 1).
There were 7361 cases of nulliparous, including 6636 (90.15%) vaginal
deliveries and 725 (9.85%) CS deliveries. In univariable analysis, women who
underwent CS delivery were more likely to be older, shorter stature, older
gestational age, greater baseline and delivery BMI, more gestational weight gain.
Women who underwent CS delivery also had more pregnancy-associated complications
and meconium-stained amniotic fluid, had a higher rate of delivering with labor
epidural analgesia, and had heavier newborn birth weight than those in the
vaginal delivery group (p
There were 2413 multiparas including 2379 (95.59%) vaginal deliveries and 34
(1.41%) CS deliveries. The maternal age, gestational age at delivery, BMI, rate
of meconium-stained amniotic fluid, rate of male fetuses, and neonatal weight of
the CS group were all higher than those of the vaginal delivery group (p
Supplementary Fig. 1 describes the study population profile. As presented in Table 2 and Fig. 1, these results were performed to assess the performance of the model in various subsets of the study.
VD | CS | AUC ROC | 95% CI | Cut-off | ||||
Tolcher | ||||||||
Original research | 554 | 231 | 0.709 | 0.671–0.750 | ||||
Validation | ||||||||
Among nulliparous | ||||||||
Augmentation group plus Induction group | 5007 | 623 | 0.702 | 0.681–0.723 | 22.9% | |||
Augmentation group | 1194 | 34 | 0.677 | 0.587–0.767 | 11.8% | |||
Induction group | 3813 | 589 | 0.659 | 0.635–0.682 | 28.6% | |||
(1) Oxytocin Induction group | 1099 | 172 | 0.635 | 0.588–0.682 | 29.1% | |||
(2) Amniotomy group | 2433 | 344 | 0.669 | 0.639–0.699 | 24.3% | |||
(3) Disposable Cervical Dilator Balloon group | 99 | 30 | 0.563 | 0.449–0.677 | ||||
(4) Prostaglandin E2 group | 182 | 43 | 0.637 | 0.540–0.735 | 48.5% | |||
Among multiparous | ||||||||
Augmentation group plus Induction group | 1487 | 30 | 0.749 | 0.656–0.842 | 24.8% | |||
Augmentation group | 354 | 3 | 0.894 | 0.770–1.018 | 13.3% | |||
Induction group | 1133 | 27 | 0.726 | 0.617–0.834 | 38.1% | |||
(1) Oxytocin Induction group | 197 | 6 | 0.821 | 0.666–0.975 | 45.5% | |||
(2) Amniotomy group | 885 | 18 | 0.674 | 0.535–0.813 | 39.5% | |||
(3) Disposable Cervical Dilator Balloon group | 42 | 3 | 0.825 | 0.677–0.974 | ||||
(4) Prostaglandin E2 group | 9 | 0 | ||||||
Levine | ||||||||
Original research | 355 | 136 | 0.77 | |||||
Validation | ||||||||
Among nulliparous plus multiparous | ||||||||
Augmentation group plus Induction group | 4074 | 477 | 0.726 | 0.704–0.748 | 25.4% | |||
Only woman with intact membranes and an unfavorable cervix | 956 | 175 | 0.697 | 0.656–0.738 | 29.0% | |||
Augmentation group | 906 | 26 | 0.672 | 0.567–0.777 | 23.6% | |||
Oxytocin Induction group | 843 | 134 | 0.691 | 0.647–0.736 | 25.4% | |||
Amniotomy group | 2097 | 257 | 0.737 | 0.708–0.766 | 25.4% | |||
Disposable Cervical Dilator Balloon group | 106 | 25 | 0.666 | 0.549–0.785 | 30.8% | |||
Prostaglandin E2 group | 122 | 35 | 0.647 | 0.540–0.755 | 60.8% | |||
Among nulliparous | ||||||||
Augmentation group plus Induction group | 2982 | 452 | 0.664 | 0.639–0.688 | 30.8% | |||
Augmentation group | 648 | 23 | 0.635 | 0.515–0.755 | 33.5% | |||
Oxytocin Induction group | 692 | 129 | 0.648 | 0.598–0.699 | 29.9% | |||
Amniotomy group | 1454 | 243 | 0.665 | 0.630–0.700 | 31.7% | |||
Disposable Cervical Dilator Balloon group | 73 | 22 | 0.630 | 0.500–0.759 | ||||
Prostaglandin E2 group | 115 | 35 | 0.626 | 0.513–0.738 | 61.7% | |||
Among multiparous | ||||||||
Augmentation group plus Induction group | 1092 | 25 | 0.638 | 0.524–0.751 | 7.6% | |||
Augmentation group | 258 | 3 | 0.577 | 0.295–0.858 | ||||
Oxytocin Induction group | 151 | 5 | 0.694 | 0.435–0.953 | 8.2% | |||
Amniotomy group | 643 | 14 | 0.645 | 0.483–0.807 | 5.2% | |||
Disposable Cervical Dilator Balloon group | 33 | 3 | 0.626 | 0.392–0.860 | ||||
Prostaglandin E2 group | 7 | 0 | ||||||
Burke | ||||||||
Original research | 1845 | 491 | 0.69 | |||||
Validation | ||||||||
Among nulliparous puls multiparous | 252 | 22 | 0.619 | 0.502–0.737 | 23.0% | |||
Among nulliparous | 180 | 19 | 0.623 | 0.500–0.746 | 23.0% | |||
VD, vaginal delivery; CS, cesarean section; AUC ROC, area under the receiver operating characteristic curve; CI, confidence interval. |
Receiver operating characteristic (ROC) curves of each model for predicting cesarean section. (A) ROC curves of Tolcher model among nulliparous. (B) ROC curves of Tolcher model among multiparous. (C) ROC curves of Levine model among nulliparous plus multiparous. (D) ROC curves of Levine model among nulliparous. (E) ROC curves of Levine model among multiparous. (F) ROC curves of Burke model.
The Tolcher model was established to evaluate the probability of CS after induction of labor among nulliparous. In this study, there were a total of 7361 cases of nulliparous. Eighteen of these women had predictors exceed the range of the nomogram. In the end, 5630 nulliparous women who experienced labor intervention were participated externally validation. The calculated AUC ROC among nulliparous after induction of labor was 0.659 (95% CI 0.635–0.682), and the probability cut-off value of 0.286 (Fig. 1A-orange line). Then, different intervention measures of labor were evaluated separately. The AUC ROC of the Augmentation group, Oxytocin Induction group, Amniotomy group and Prostaglandin E2 group were 0.677, 0.635, 0.669 and 0.637, respectively (Fig. 1A).
Multiparas in the study were also evaluated. Among these women, the AUC ROC of the Induction group, Augmentation group, Oxytocin Induction group and Amniotomy group were 0.726, 0.894, 0.821 and 0.674, respectively (Fig. 1B). While the difference in the prediction probabilities of the Disposable Cervical Dilator Balloon group and Prostaglandin E2 group were not statistically significant.
The Levine model was developed to assess the probability of CS
for women (nulliparous plus multiparous)
undergoing an induction of labor with intact membranes and an unfavorable cervix.
In this study, there were 3575 cases of baseline BMI less than 20 kg/m
The Burke model was developed to calculate the probability of CS in nulliparous
woman from 39
With the change of China’s one-child policy, an increasing number of researchers and pregnant women are commonly and widely concerned about the choice of delivery mode. The ability to predict the risk of CS for women with singleton, term and cephalic pregnancies would be highly beneficial to guide their management in labor. We searched the literature for models that predicted the probability of CS delivery among women with singleton, term, and cephalic pregnancies during the same period as our study. Three models with relatively high quality and large sample size were included. But, the effectiveness of a new predictive model must be evaluated before it put into clinical practice. Thus, we externally validated these models (Tolcher, Levine, and Burke models) in an existing cohort of Chinese women. At the same time, nulliparous and multiparous were evaluated separately. Different methods of induction were verified as well.
Unfortunately, under these specific conditions, the predictive abilities of
three models were mostly poor (AUC ROC
We also preliminarily explored some variables that might be useful in predicting the risk of CS. In our study, maternal age, height, BMI, weight gain during pregnancy, gestational age, mode of labor induction, meconium-stained amniotic fluid, presence of complications, neonatal birth weight, and neonatal gender affected the delivery mode. Previous studies have shown that these factors at least partly determine the incidence of CS [11, 12, 13], and the gestational age of induced labor also affects it [14].
As far as we know, this is the first study to simultaneously concluding validations of above these three models for predicting CS delivery at term in Chinese population. These models were validated not only in a standard population, but also in multiparas. Unfortunately, the results suggest that these models are not suitable for the target population. The results are negative, but they show the necessity of validating existing models in different settings and populations before widespread implementation in clinical practice. The results also indicate that models need to be established locally and ethnically. Most prediction models may be only applicable to the specific populations which the original models normally target on. Additionally, further investigation of model validity and impact is important and should be undertaken.
Some limitations in this study should also be acknowledged. Firstly, the sample
size was small, and this study had a retrospective design. Because of limitations
of the quality of case records, some data is inevitably missing and inherently
biased. Second, the cervical ripening was assessed by only cervical dilation
during induction. We found in the literature review that Levine et al.
[7] optimized their previous prediction model. The following five variables,
which were modified Bishop score, gestation age
At present, many prediction models were established in many medical fields, but few are maturely implemented in clinical care. The performance, impact, and usefulness of prediction models need to be supported prior to practice [17]. Three models were externally validated in our center, but the results were not satisfactory. Given the diversity of geography, economy, medical level and environment across China, it is unclear whether these models can be applied to medical centers in other parts of the country. With the development of data technology, it is expected to conduct a large sample, multicenter, prospective study in China. And prediction models should be established accurately, conveniently and locally. It is worth noting that these models should not be used in isolation, but should be combined with the actual conditions of patients.
The Tolcher, Levine and Burke models for predicting CS may not be suitable for Chinese population in this hospital, but the applicability of these models in this population needs to be further explored with a larger samples and more centers. It is also necessary to ensure high quality and safe delivery for all childbearing women. In addition, maternal age, height, BMI, weight gain during pregnancy, gestational age, mode of labor induction, meconium-stained amniotic fluid, presence of complications, neonatal weight, and neonatal gender affected the delivery mode.
All authors contributed to the creation of the article as follows: BH had the original idea of the study. FCS, MHS, YGC and FFW contributed to data collection. FCS and MHS analyzed the data. FCS wrote the first draft of the paper. BH and FCS provided critical review and interpretation of the results. BH provided professional language. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript.
The protocol for this study was approved by The Institutional Review Board at this center (2018019). As this study is a retrospective study, all individuals participating in the study are exempted from informed consent.
We would like to express our gratitude to all those who helped us in the research.
This research received no external funding.
The authors declare no conflict of interest.