The cascade of
spontaneous events that sets the wheels of labor in motion has remained a
mystery despite all the recent advances in the field of maternal and fetal medicine.
Researchers hypothesize that it’s blend of physiology and magic that sets the
ball rolling. Maternal and fetal signals both play a part in starting the process.
The history
of labor induction dates to time of Hippocrates' when mammary stimulation
and mechanical cervical dilatation was used to bring about uterine contraction.[1]
Induction of labor for singleton births has seen a slight decline from 23.8% in
2010 and 23.3% in 2012 after seeing a steady increase in past 20 years. [2]
This translate to 932,000 women
undergoing induction of labor for various maternal and fetal indication.
Various
mechanical and chemical methods singly or in combination have been in use since
long. The choice of method depends on state of cervix, previous obstetric
history, indication of induction and gestational age at induction. Foley’s balloon
catheter, Prostaglandin E2 and misoprostol are common methods used for cervical
ripening. Amniotomy and oxytocin are used when the cervix is already ripened.[3]
A recent
paper published on November 03, 2016 in Journal of Obstetrics & Gynecology
evaluated the effectiveness of the four most commonly used method. [4]
The paper was also presented at the Pregnancy Meeting, the 2016 Annual Meeting
of the Society for Maternal-Fetal Medicine (SMFM).
Dr. Lisa Levine,
MD, University of Pennsylvania’s Perelman School of Medicine, Philadelphia,
Pennsylvania, and colleagues said in their presentation “This randomized trial
is one of the first of its kind to compare 4 different induction methods in a
head-to-head trial. We found that combination induction methods resulted in
delivery in half the amount of time as single agents with no difference in
caesarean delivery rates.”
The study called
as Foley or Misoprostol for the Management of Induction (FOR MOMI) trial was a 4-armed
randomized trial conducted between May 2013 and June 2015. The study recruited 492 women
with singleton full-term pregnancy (37 weeks of gestation or greater), vertex-presentation,
with no contraindication to vaginal delivery, intact membranes, Bishop score 6
or less, and cervical dilation 2 cm or less. These women were assigned to receive
either misoprostol alone; or Foley catheter alone; Foley catheter and Pitocin
concurrently or misoprostol and cervical Foley catheter concurrently.
The primary
outcome measured was reduction in time to delivery with a reduction of more
than 4 hours considered significant. Numerous secondary outcomes like time to
vaginal delivery, rate of caesarean deliveries, time in active labor, defined
as cervical dilation of 5 cm or more, delivery within 12 or 24 hours, and
maternal length of stay were also looked at.
The demographics
and clinical characteristics of the study participants were quite similar with
a mean age of 27 years, 72% being nullipara, mean gestational age at induction
being 39 weeks with mean bishop score 3 and mean cervical dilatation 1.
The median time
to delivery for nulliparous and multiparous women in various arms of the study are
(P<.001):
misoprostol–Foley
group 13.1 hours
oxytocin–Foley group 14.5 hours
misoprostol only 17.6 hours
Foley-only group 17.7 hours
When
the data was adjusted for parity and only vaginal deliveries analyzed, women in
the misoprostol-Foley group where twice as likely to deliver earlier (HR=1.92)
with reference to misoprostol only or Foley-only group.
Women
in the combination arms of the study also had the maximum chance of delivering
in 24 hours. (88% of women in the misoprostol/Foley group and 84% in the
oxytocin/Foley group).
Rates
of cesarean section and other maternal morbidities like perineal lacerations, endometritis,
wound infection and dehiscence, readmission or length of stay were comparable
in all the groups. No significant difference was found in neonatal morbidities
too.
The
authors opined that “This study has significant clinical implications for
obstetric care. The ability to shorten the length of time women spend in labor
without increasing morbidity has large clinical and financial implications
given the cost and known maternal–neonatal risks associated with both prolonged
labor and cesarean delivery."
The
only study limitation was lack of blinding, because women had to be examined for
application of different methods in 4 study arms. Also, individual arm lacked
the statistical power to compare the cesarean section, maternal and neonatal
morbidities across different groups.
In all,
the findings could help millions of women and shorten thousands of hours in
labor across the world. It is estimated that nearly 20% or 932,000 women
undergo induction of labor in USA. If combination method is used in all of
them, then there would be more than 3 million fewer hours, or more than 125,000
fewer days that women spend in labor in the United States alone.
This has huge financial
and health care utilization implications.
[1] www.glowm.com/section_view/heading/Induction%20of%20Labor/item/130
[2] http://www.cdc.gov/nchs/data/databriefs/db155.pdf
[3] https://sogc.org/wp-content/uploads/2013/08/September2013-CPG296-ENG-Online_REV-D.pdf
[4] http://journals.lww.com/greenjournal/Abstract/publishahead/Mechanical_and_Pharmacologic_Methods_of_Labor.98564.aspx
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