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