Failed induction of labor

Induction of labor is a widely used practice. From 2016 to 2019, >1 in 3 women giving birth in the United States did so after undergoing labor induction. The obvious goal of labor induction is vaginal birth with minimal maternal or neonatal morbidity. To achieve this goal, criteria for failed labor induction are needed. Herein, we provide an evidence-based approach to safely prevent unnecessary cesarean deliveries for failed induction. Although there are no randomized trials comparing failed labor induction criteria, the observational data have been consistent: if the status of the mother and the fetus permits, at least 12 to 18 hours of oxytocin should be administered after membrane rupture before deeming an induction of labor to have failed because of nonprogression to the active phase of labor.

Risk of Cesarean Delivery for Women with Obesity Using a Standardized Labor Induction Protocol

OBJECTIVE

We aimed to determine the risk of cesarean among women with obesity undergoing labor induction within a prospective trial that utilized a standardized labor protocol.

STUDY DESIGN

This was a secondary analysis of a randomized trial of induction methods. Term (≥37 weeks) women with intact membranes undergoing induction with an unfavorable cervix (Bishop's score ≤6 and dilation ≤2 cm) were included. The trial utilized a labor protocol that standardized induction and active labor management, with recommendations for interventions at particular time points. Only women with a recorded body mass index (BMI) at prenatal care start were included in this analysis. The primary outcome was cesarean delivery compared between obese (≥30 kg/m²) and nonobese (<30 kg/m²) women. Indication for cesarean was also evaluated.

RESULTS

A total of 465 women were included: 207 (44.5%) obese and 258 (55.5%) nonobese. Women with obesity had a higher risk of cesarean compared with women without obesity (33.3 vs. 23.3%, p = 0.02), even when adjusting for parity, weight change over pregnancy, and indication for induction (adjusted relative risk [aRR] = 1.79, 95% confidence interval [CI]: [1.34-2.39]). Compared with women without obesity, women with obesity had a higher risk of failed induction (47.8 vs. 26.7%, p = 0.01) without a difference in arrest of active phase (p = 0.39), arrest of descent (p = 0.95) or fetal indication (p = 0.32), despite adherence to a standardized labor protocol.

CONCLUSION

Compared with women without obesity, women with obesity undergoing an induction are at increased risk of cesarean, in particular a failed induction, even within the context of standardized induction management. As standardized practices limit provider variation in labor management, this study may support physiologic differences in labor processes secondary to obesity.

KEY POINTS

· Even with a standardized induction protocol, women with obesity are at higher risk of cesarean.. · In particular, women with obesity are at increased risk of cesarean for failed induction.. · These findings support a possible biologic relationship between obesity and failed induction..

Association between long interpregnancy intervals and cesarean delivery due to arrest disorders

BACKGROUND

It is hypothesized that pregnancy causes time-limited physiologic adaptations of the reproductive system, such as increased blood flow to the uterus. With long interpregnancy intervals, those adaptations may regress, and maternal physiologic characteristics may revert to those of primigravid women. Therefore, it is plausible that long interpregnancy interval is associated with cesarean delivery, especially due to arrest disorders (failed induction of labor, arrest of dilation, or arrest of descent).

OBJECTIVE

To examine the association between interpregnancy interval and cesarean delivery due to arrest disorders in multiparous women without a history of cesarean delivery.

MATERIALS AND METHODS

This was a retrospective cohort study of all women who had more than 1 singleton pregnancy at 23 weeks' gestation or greater at MedStar Washington Hospital Center from January 2009 to June 2018. We defined the interpregnancy interval as the duration from the birth of the preceding offspring to the date of conception of the index offspring. We a priori decided to categorize women based on the interpregnancy interval (less than 18 months, 18-59 months, and 60 months or greater). Our primary outcome was cesarean delivery due to arrest disorders. We also examined overall cesarean delivery and cesarean delivery due to nonreassuring fetal heart tracing. Multivariable logistic regression was performed to calculate adjusted odds ratios and 95% confidence intervals, controlling for predefined covariates.

RESULTS

Of 2741 women, 1143 (41.7%), 1369 (49.9%), and 229 (8.4%) had an interpregnancy interval of less than 18 months, 18-59 months, and 60 months or more, respectively. After adjusting for confounders, an interpregnancy interval of 60 months or more compared to an interpregnancy interval of 18-59 months was associated with increased odds of cesarean delivery due to arrest disorders (4.8% vs 1.3%; adjusted odds ratio, 3.06; 95% confidence interval, 1.34-6.97) and cesarean delivery due to arrest of dilation (3.1% vs 0.7%; adjusted odds ratio, 3.24; 95% confidence interval, 1.10-9.59). An interpregnancy interval of less than 18 months compared to an interpregnancy interval of 18-59 months was associated with decreased odds of cesarean delivery due to nonreassuring fetal heart tracing (2.4% vs 4.1%; adjusted odds ratio, 0.55; 95% confidence interval, 0.32-0.92).

CONCLUSION

An interpregnancy interval of 60 months or greater compared to an interpregnancy interval of 18-59 months was associated with increased odds of cesarean delivery due to arrest disorders. Beneficial effects on postpartum adaptations in the reproductive system may regress as interpregnancy interval increases.

Impact of recommended changes in labor management for prevention of the primary cesarean delivery

BACKGROUND

The dramatic rise in cesarean delivery rates worldwide in recent decades, without evidence of a concomitant decrease in cerebral palsy rates, has raised concerns about its potential negative consequences for maternal and infant health. In 2014, the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine jointly published an Obstetric Care Consensus for safe prevention of the primary cesarean delivery.

OBJECTIVE

We sought to assess whether modification of our protocol to implement these recommendations helped to decrease our primary cesarean delivery rate safely.

STUDY DESIGN

This is a before-and-after retrospective cohort study at a university referral hospital. In March 2014, the threshold for defining active labor changed from 4 to >6 cm and arrest of first-stage labor from lack of cervical change despite regular contractions after 3 hours of oxytocin administration with amniotomy and epidural anesthesia to no change after 4 hours of adequate or 6 hours of inadequate contractions in women with an epidural. The definition of second-stage arrest of labor changed simultaneously from lack of progress for 3 hours with adequate contractions in women with epidural anesthesia to no progress for ≥4 hours in nulliparas or 3 hours in multiparas with an epidural. We compared maternal and neonatal outcomes over two 1 year periods: from March 2013 to February 2014 (before, preguideline) and from June 2014 to May 2015 (after, postguideline). We included all women with singleton pregnancies at ≥37 weeks' gestation, in vertex presentation, in spontaneous or induced labor, and with epidural anesthesia. We excluded women with an elective or previous cesarean delivery and those with obstetric or fetal complications.

RESULTS

This study included 3283 and 3068 women in the before and after periods, respectively. The groups had similar general and obstetric characteristics. The global cesarean delivery rate decreased significantly from 9.4% in the preguideline to 6.9% in the postguideline period (odds ratio, 0.71; 95% confidence interval, 0.59-0.85; P < .01). The cesarean delivery rate for arrest of first-stage labor fell by half, from 1.8% to 0.9% (odds ratio, 0.51; 95% confidence interval, 0.31-0.81; P < .01) but was significant only among nulliparous women. The cesarean delivery rate for second-stage arrest of labor decreased but not significantly between periods (1.3% vs 1.0%; odds ratio, 0.73; 95% confidence interval, 0.44-1.22; P = .2), and the cesarean delivery rate for failure of induction remained similar (3.7% vs 3.5%; odds ratio, 1.06; 95% confidence interval, 0.06-13.24; P = .88). The median duration of labor before cesarean delivery also became significantly longer among nulliparous women during the later period. Maternal and neonatal outcomes did not differ between the 2 periods, except that the rate of 1 minute Apgar score <7 fell significantly in the later period (8.4% vs 6.9%; odds ratio, 0.80; 95% confidence interval, 0.66-0.97; P = .02).

CONCLUSION

The modification of our protocol by implementing the new consensus recommendations was associated with a reduction of the rate of primary cesarean delivery performed for arrest of labor with no apparent increase in immediate adverse neonatal outcomes in nulliparous women at term with singleton pregnancies in vertex presentation and with epidural anesthesia. Further studies are needed to assess the long-term maternal and neonatal safety of these policies.

A validated calculator to estimate risk of cesarean after an induction of labor with an unfavorable cervix

BACKGROUND

Induction of labor occurs in >20% of pregnancies, which equates to approximately 1 million women undergoing an induction in the United States annually. Regardless of how common inductions are, our ability to predict induction success is limited. Although multiple risk factors for a failed induction have been identified, risk factors alone are not enough to quantify an actual risk of cesarean for an individual woman undergoing a cesarean.

OBJECTIVE

The objective of this study was to derive and validate a prediction model for cesarean after induction with an unfavorable cervix and to create a Web-based calculator to assist in patient counseling.

STUDY DESIGN

Derivation and validation of a prediction model for cesarean delivery after induction was performed as part of a planned secondary analysis of a large randomized trial. A predictive model for cesarean delivery was derived using multivariable logistic regression from a large randomized trial on induction methods (n = 491) that took place from 2013 through 2015 at an academic institution. Full-term (≥37 weeks) women carrying a singleton gestation with intact membranes and an unfavorable cervix (Bishop score ≤6 and dilation ≤2 cm) undergoing an induction were included in this trial. Both nulliparous and multiparous women were included. Women with a prior cesarean were excluded. Refinement of the prediction model was performed using an observational cohort of women from the same institution who underwent an induction (n = 364) during the trial period. An external validation was performed utilizing a publicly available database (Consortium for Safe Labor) that includes information for >200,000 deliveries from 19 hospitals across the United States from 2002 through 2008. After applying the same inclusion and exclusion criteria utilized in the derivation cohort, a total of 8466 women remained for analysis. The discriminative power of each model was assessed using a bootstrap, bias-corrected area under the curve.

RESULTS

The cesarean delivery rates in the derivation and external validation groups were: 27.7% (n = 136/491) and 26.4% (n = 2235/8466). In multivariable modeling, nulliparity, gestation age ≥40 weeks, body mass index at delivery, modified Bishop score, and height were significantly associated with cesarean. A nomogram and calculator were created and found to have an area under the curve in the external validation cohort of 0.73 (95% confidence interval, 0.72-0.74).

CONCLUSION

A nomogram and user-friendly Web-based calculator that incorporates 5 variables known at the start of induction has been developed and validated. It can be found at: http://www.uphs.upenn.edu/obgyn/labor-induction-calculator/. This calculator can be used to augment patient counseling for women undergoing an induction with an unfavorable cervix.