When to make the diagnosis of failed induction of labor after Oxytocin and Rupture of membranes?

Clinical Pearls:

• In Nulliparous women 12 hours of Oxytocin and Rupture of membranes is optimum before diagnosing an unsuccessful induction. The neonates of women who remained in latent phase past 12 hours have increased rate of NICU admissions.
• In Multiparous women 15 hours of Oxytocin and Rupture of membranes is optimum before diagnosing an unsuccessful induction. The neonates of women who remained in latent phase past 15 hours have increased rate of NICU admissions.
• The longer women remained in latent phase with Oxytocin and Rupture of Membranes, the risk of maternal and neonatal complication increased.

According to CDC between 1990 and 2011 the rate for labor induction have more than doubled rising from 9.5% to 23.2%. About 762,000 induction of labor were performed making it one of the most commonly performed obstetric procedure in US.[1]

There is no accepted definition of “failed induction of labor”, although the ACOG in its statement to bring down the cesarean section rate does quote “cesarean deliveries for failed induction of labor in the latent phase can be avoided by... requiring that oxytocin be administered for at least 12–18 hours after membrane rupture before deeming the induction a failure.”[2] However this recommendation by ACOG is based on limited studies with very small study population. [3] In the two studies on which the recommendation is based 17- 60% of the women had vaginal delivery after still being in latent phase after 12 hours. [4] [5]

A Joint statement issued by Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, and American College of Obstetricians and Gynecologists Workshop quotes that “The diagnosis of failed induction should only be made after an adequate attempt. Failed induction is defined as failure to generate regular (eg, every 3 minutes) contractions and cervical change after at least 24 hours of oxytocin administration with artificial membrane rupture if feasible.”[6] But, with the latent phase extending long, maternal and neonatal safety concerns are constantly raised.

A recent retrospective cohort study published in Journal of Obstetrics and Gynecology compared neonatal and maternal outcome in relation to oxytocin induction and rupture of membranes before the active phase of labor (Cervical dilatation > 6 cm). This large study used the data from Consortiumon Safe Labor (CSL) which is a consortium of 12 clinical institutions providing data on labor and newborn to create a perinatal database with more than 200,000 deliveries. The de-identified database is than used for secondary data analysis to answer several obstetrics questions.

The study data included 9,763 nulliparous and 8,379 multiparous women, carrying singleton term pregnancies, with unfavorable cervix. In all these women labor was induced at 2 cm dilatation or less to 6 cm dilatation with rupture of membrane.  6 cm was taken as cut-off because women entered into active phase of labor once they crossed the 6 cm dilatation. No cervical ripening agent was used in the women included in the study.

The clinical outcomes evaluated included vaginal delivery rates, maternal and neonatal morbidity including NICU admissions. Women were assessed at fixed intervals of 6, 9, 12, 15, and 18 hours post oxytocin and rupture of membranes in regards to cervical dilatation, contraction, vaginal delivery or cesarean delivery. Time was marked zero hour when oxytocin and rupture of membrane both were present.

Hypertensive disorders of pregnancy were the most common indication for induction of labor in nulliparous (21.8%) and multiparous patients (10.7%) followed by post-date pregnancy.

At the end of 12 hours most of the nulliparous women have entered the active phase or have delivered with only 6.5% still in the latent phase, while at 15 hours only .6% multiparous women were still in the latent phase.

Eventually, out of this group 36.6% of the nulliparous and 50.0% of multiparous women had vaginal birth.  Those nulliparous women who still were in latent phase of labor at the end of 12 or 15 hours had high rates of maternal and neonatal complications. For multiparous patients who were still laboring at the end of 15 hours had increased maternal complications but the rate of NICU admission were not statistically significant.

The longer the patients remained in the latent phase with rupture of membranes and oxytocin, chances of vaginal delivery decreased proportionately and maternal and neonatal complications increased as time progressed. Maternal complications include chorioamnionitis, PPH and endometritis while neonatal complications include neonatal sepsis and NICU admissions.

The large cohort of patient’s data drawn from diverse population powered the study sufficiently to study a variety of outcomes including neonatal morbidity and NICU admission associated with longer duration of oxytocin and rupture of membranes. It also increased the generalizability of the study. Labor management is not standardized across the hospitals which may have led to cesarean deliveries in latent phase without waiting longer.

It was seen that the longer women remained in latent phase with Oxytocin and Rupture of Membranes, the risk of maternal and neonatal complication increased. Because of the retrospective nature of the data, diagnosis of failed induction cannot be made but 12 hours of Oxytocin and rupture of membranes in Nulliparous and 15 hours in Multiparous patient is a reasonable cutoff, because neonatal morbidity rises after that.

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[1] http://www.cdc.gov/nchs/fastats/obstetrical-procedures.htm

[2] Safe prevention of the primary cesarean delivery. Obstetric Care Consensus No. 1. American College of Obstetricians and Gynecologists. Obstet Gynecol 2014;123:693–711

[3] http://www.acog.org/Resources-And-Publications/Obstetric-Care-Consensus-Series/Safe-Prevention-of-the-Primary-Cesarean-Delivery

[4] Rouse DJ, Owen J, Hauth JC. Criteria for failed labor induction: prospective evaluation of a standard protocol. Obstet Gynecol 2000;96:671–7

[5] Simon CE, Grobman WA. When has an induction failed? Obstet Gynecol 2005;105:705–9

[6] http://journals.lww.com/greenjournal/Fulltext/2012/11000/Preventing_the_First_Cesarean_Delivery__Summary_of.26.aspx