Maternal and perinatal outcome of induction at 39 weeks versus expectant management in labor after cesarean section

To study induction of labor (IOL) at 39 weeks compared with expectant management among women undergoing labor after cesarean section (LAC) with no prior vaginal delivery.


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MEYER and LEVIn adverse maternal outcomes including, among others, the risk of uterine rupture, ranging 0.3-0.7%. [7][8][9] Moreover, several methods of IOL are associated with an increased risk of uterine rupture in women with previous CS, reaching as much as two to threefold. 6,10 Therefore, IOL in LAC may pose a true clinical dilemma. Generally, IOL among women undergoing LAC is performed for medical indications. 11 However, considering the results of the ARRIVE trial, it is interesting to study whether the same effects observed following IOL at 39 weeks are present among women undergoing LAC when compared to expectant management. Currently, literature regarding this topic is lacking.
The purpose of this study is to compare LAC outcomes of women with no prior vaginal delivery that are undergoing IOL at 39 0/7 to 39 6/7 weeks of gestation with LACs occurring at ≥40 0/7 .

| Patients
This is a retrospective cohort study. The study cohort consisted of women undergoing a LAC with no prior vaginal delivery. All deliveries occurred at one tertiary medical center, from March 2011 to March 2020. We included women with a live singleton fetus in vertex presentation, with one prior low transverse uterine incision.
We excluded women with more than one prior CS. We allocated the study cohort into two groups: IOL at 39 0/7 to 39 6/7 and all LACs occurring at ≥40 0/7 weeks of gestation. A further analysis compared IOL at 39 0/7 to 39 6/7 to IOL at ≥40 0/7 weeks of gestation.
Methods for IOL included oxytocin administration, extraamniotic balloon and amniotomy. Oxytocin is administrated at a rate of 1 milliunit per minute, with gradual increase of 1-1.25 milliunits per minute every 30 minutes to a maximal rate of 15 milliunits per minute. Extraamniotic balloon insertion is performed as follows: we administer a 22F Foley catheter through the cervix under direct visualization with the use of a sterile vaginal speculum. Before insertion, the cervix is cleansed with aseptic solution. Once the catheter passes the internal os, the balloon is inflated with 40-60 mL 0.9% NaCl solution, and the external end of the catheter is taped to the inner part of one of the thighs.
The primary outcome of the study was a composite of adverse neonatal outcomes including any of the following: Apgar scores <5 at 1 minute and <7 at 5 minutes, umbilical cord arterial pH <7, umbilical cord arterial base excess ≥12 mEq, neonatal intensive care unit (NICU) admission, mechanical ventilation use, hypoxic ischemic encephalopathy, and hospital length of stay >6 days after delivery. Secondary outcomes included a composite of adverse maternal outcomes including uterine rupture, postpartum hemorrhage, and length of stay of >4 days after delivery. An additional secondary outcome was the mode of delivery.

| Data collection
We collected the following variables from the electronic health record: maternal characteristics including maternal age, immigration and smoking status, body mass index (BMI) at admission to delivery unit, height and gestational weight gain, diabetic and hypertensive disorders; prior CS characteristics including gestational age at delivery, indications for the prior CS, cervical dilation and labor stage at prior CS, and birthweight at prior CS; current delivery characteristics including gestational age at delivery, sonographic estimated fetal weight, inter-delivery interval from prior CS, oxytocin administration, epidural analgesia, presence of meconium-stained amniotic fluid and intrapartum fever; mode of delivery and indication for unplanned CS; maternal outcomes including uterine rupture, postpartum hemorrhage, length of stay after delivery; neonatal characteristics and outcomes including birthweight, birthweight percentile, Apgar scores at 1 and 5 minutes, arterial pH and base excess, NICU admission, need for mechanical ventilation, hypoxic ischemic encephalopathy and length of stay after delivery.
We defined hypertensive disorders of pregnancy according to the American College of Obstetricians and Gynecologists (ACOG), integrating gestational hypertension and preeclampsia. 12 Diabetic disorders were defined as either pregestational diabetes, in accordance with the American Diabetes Association criteria, 13 or gestational diabetes mellitus, based on the diagnostic thresholds established by Carpenter and Coustan. 14 We defined intrapartum fever as temperature of at least 38.0° Celsius that persists when the temperature is repeated after 30 minutes or a single oral temperature of 39°C (102.2 F). 15,16 Birthweight percentiles were calculated using local, population-based live-born infants' birth weight curves. 17

| Statistical analysis
We performed univariable analysis using Chi square test and Fisher's exact test as appropriate. We used the student t-test for analysis of continuous variables with normal distribution and the Mann-Whitney U test for analysis of continuous variables with skewed distribution.
Multivariable logistic regression analysis was used to adjust for potential confounding factors for adverse maternal outcomes including IOL, maternal age, BMI, presence of diabetic or hypertensive disorders.
Factors were reported as odds ratio (OR) and 95% confidence interval (CI). Potentially associated factors included those identified by univariate analysis (P <0.05). A two-sided P <0.05 indicated statistical significance. The data were analyzed using Software Package for Statistics and Simulation (IBM SPSS version 27, IBM Corp., Armonk, NY).

| Ethical approval
The study protocol was approved by the institutional review board

| Maternal characteristics
Mean maternal height was higher in the IOL as compared to the LAC at ≥40 weeks group (162 vs. 163 cm. P = 0.019), and maternal gestational weight gain was lower in the IOL group (12 vs. 13 kg, P = 0.013). The proportion of women with diabetic disorders and hypertensive disorders was higher in the IOL group compared to the LAC at ≥40 weeks group (16.9% vs. 4.7% and 6.7% vs. 1.6%, P <0.001 and P = 0.001, respectively).

| Previous cesarean section characteristics
Mean gestational age at previous CS was lower in the IOL group (37 6/7 vs . 38 4/7, P = 0.003). Cervical dilation at previous CS was lower in the IOL group compared to the LAC at ≥40 weeks group (mean 3 cm vs. 4 cm, P = 0.021).

| LAC characteristics
Sonographic estimated fetal weight was lower in the IOL group (3139 vs. 3363 g, P <0.001).
The proportion of LACs with oxytocin administration at any time was higher in the IOL group (67.4% vs. 24.4%, P <0.001). The proportion of meconium-stained amniotic fluid was lower in the IOL amniotomy group (13.5% vs. 27.0%, P = 0.005).

| Maternal outcome
There were three uterine ruptures (3.4%) in the IOL group and 11 (1.2%) in the LAC at ≥40 weeks group (P = 0.115). The rate of composite maternal outcomes occurrence was higher in the IOL group (18.0% vs. 10.1%, P = 0.022).

| Neonatal outcomes
Birthweight was lower in the IOL group compared to the LAC at  IOL with prostaglandins, which is associated with increased risk of uterine rupture, 25 is not performed in our center among women undergoing LAC.

| CON CLUS ION
In summary, IOL at 39 weeks of gestation among women undergoing LAC with no prior vaginal delivery is not associated with improved neonatal outcomes as compared to expectant management.
However, it may be associated with an increase in adverse maternal outcomes. Women undergoing medically indicated IOL following CS should be made aware of the increase in maternal risks related to the induction. Our results may serve as a decision support tool among women undergoing LAC when IOL is considered.

AUTH O R CO NTR I B UTI O N S
GL and RM reviewed the literature, collected data and wrote the paper.

CO N FLI C T S O F I NTE R E S T
None.

DATA AVA I L A B I L I T Y S TAT E M E N T
No. Research data are not shared.