Background
While there are well-accepted standards for the diagnosis of arrested active-phase
labor, the definition of a “failed” induction of labor remains less certain. One approach
to diagnosing a failed induction is based on the duration of the latent phase. However,
a standard for the minimum duration that the latent phase of a labor induction should
continue, absent acute maternal or fetal indications for cesarean delivery, remains
lacking.
Objective
The objective of this study was to determine the frequency of adverse maternal and
perinatal outcomes as a function of the duration of the latent phase among nulliparous
women undergoing labor induction.
Study Design
This study is based on data from an obstetric cohort of women delivering at 25 US
hospitals from 2008 through 2011. Nulliparous women who had a term singleton gestation
in the cephalic presentation were eligible for this analysis if they underwent a labor
induction. Consistent with prior studies, the latent phase was determined to begin
once cervical ripening had ended, oxytocin was initiated, and rupture of membranes
had occurred, and was determined to end once 5-cm dilation was achieved. The frequencies
of cesarean delivery, as well as of adverse maternal (eg, postpartum hemorrhage, chorioamnionitis)
and perinatal (eg, a composite frequency of seizures, sepsis, bone or nerve injury,
encephalopathy, or death) outcomes, were compared as a function of the duration of
the latent phase (analyzed with time both as a continuous measure and categorized
in 3-hour increments).
Results
A total of 10,677 women were available for analysis. In the vast majority (96.4%)
of women, the active phase had been reached by 15 hours. The longer the duration of
a woman’s latent phase, the greater her chance of ultimately undergoing a cesarean
delivery (P < .001, for time both as a continuous and categorical independent variable), although
>40% of women whose latent phase lasted ≥18 hours still had a vaginal delivery. Several
maternal morbidities, such as postpartum hemorrhage (P < .001) and chorioamnionitis (P < .001), increased in frequency as the length of latent phase increased. Conversely,
the frequencies of most adverse perinatal outcomes were statistically stable over
time.
Conclusion
The large majority of women undergoing labor induction will have entered the active
phase by 15 hours after oxytocin has started and rupture of membranes has occurred.
Maternal adverse outcomes become statistically more frequent with greater time in
the latent phase, although the absolute increase in frequency is relatively small.
These data suggest that cesarean delivery should not be undertaken during the latent
phase prior to at least 15 hours after oxytocin and rupture of membranes have occurred.
The decision to continue labor beyond this point should be individualized, and may
take into account factors such as other evidence of labor progress.
Key words
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Article Info
Publication History
Published online: November 11, 2017
Accepted:
November 6,
2017
Received in revised form:
October 27,
2017
Received:
October 2,
2017
Footnotes
The project described was supported by grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development ( HD21410 , HD27869 , HD27915 , HD27917 , HD34116 , HD34208 , HD36801 , HD40500 , HD40512 , HD40544 , HD40545 , HD40560 , HD40485 , HD53097 , HD53118 ) and the National Center for Research Resources ( UL1 RR024989 ; 5UL1 RR025764 ). Comments and views of the authors do not necessarily represent views of the National Institutes of Health.
The authors report no conflict of interest.
Cite this article as: Grobman WA, Bailit J, Lai Y, et al. Defining failed induction of labor. Am J Obstet Gynecol 2018;218:122.e1-8.
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