Since last 30 years, we have seen a trend of increasing
number of women delaying childbirth till later in life, especially in
industrialized nation . In a span of 10 years, births to
women 35 years and older increased from 12% to 20% in UK.
Women 35 years and
older are at increased risk of antepartum, intrapartum and postnatal
complications like hypertensive disease,
gestational diabetes mellitus, placenta previa, and placental abruption and
perinatal deaths. They are also at risk of delivering macrosomic or low birth weight
infants.
The rate of obstetrical intervention and caesearean
deliveries also rises with maternal age, being 38% in nulliparous women over 35
and nearly 50% in those over 40 years of age.
According to Smith GCS et al the gestational week of
delivery associated with the lowest cumulative risk of perinatal death was 38
weeks' gestation and the risk of death increased more sharply among primigravid
women after 38 weeks' gestation because of a greater risk of antepartum
stillbirth.
Currently, in the absence of maternal and fetal complication,
routine induction is available to all women in U.K at 41-42 weeks when the risk
of still birth is 2-3/1000 live births. However, based on many observational
studies, it is a general consensus among obstetrician that induction leads to
increased rate of caesarean deliveries and increased perinatal complications.
Trials of induction of labour at term are mostly in women
with complications like hypertension, prelabor rupture of membranes, fetal
growth restriction, diabetes, or fetal macrosomia. Only few trials involving
women with no complications are found in literature, but lack power and are in
1970s. Trials of induction of labour due to advanced maternal age are
lacking
This 35/39 trial was designed to test the hypothesis that
induction of labour at 39 weeks in older nulliparous women reduces the risk of
operative delivery. The results of the trial was published in March 3, 2016
issue of New England Journal of medicine.
The investigators performed a multicenter, randomized,
controlled trial to compare the rate of cesarean section between women who were induced at 39 weeks and 0 days
– 39 weeks and 6 days ( n= 304) with
those who were managed expectantly(n=314). Inclusion criteria were
nulliparity, age 35 years or older and carrying a single fetus in cephalic
presentation.
The primary outcome was cesarean section and the secondary
outcome being other form of vaginal deliveries, onset of labour, augmentation
of labour , intrapartum , postpartum and neonatal complications.
The induction of labour was done according to the protocols
of the units, but most used prostaglandin ripening followed, if necessary, by
amniotomy and oxytocin infusion.
It was seen that there was no significant difference in the
rate of cesarean sections between the induction group
(98 of 304 women [32%]) vs. (103 of 314 women [33%]) in the expectant group.
Also a total of 115 of 304 women (38%) in the induction group delivered
vaginally as compared with 104 of 314 women (33%) in the expectant-management
group.
The results were also comparable across different maternal
age group according to a sub group analysis.
The authors acknowledge the limitations of the trials "the
results may not be generalizable to older multiparous women and may not apply
to all nulliparous pregnant women who are 35 years of age or older."
The authors further say that “Our trial did not address
whether induction of labor at 39 weeks of gestation can prevent stillbirths. It
does, however, provide support for the safety of performing a larger trial to
test the effects of induction on stillbirth and uncommon adverse neonatal
outcomes in women 35 years of age or older, although such a trial would need to
be extremely large.”
The journal article was also accompanied by an editorial by William
A. Grobman, M.D, from the Northwestern University Feinberg School of Medicine
in Chicago, Illinois,
he emphasized that “it would be premature to alter recommendations
regarding the timing of delivery in uncomplicated pregnancies. Although the
study did not show evidence of harm from induction at 39 weeks of gestation, it
also did not show evidence of benefit, and one could argue that medical
interventions in general, and intervention in the natural progress of gestation
specifically, should be performed only when benefit has been shown.”
He also stressed that the study lacked sufficient power to
analyze differences in perinatal outcomes, whether labor induction at 39 weeks
of gestation affects these outcomes remains unknown!
He further added “The trial makes an important contribution
to medical knowledge. It is the largest trial of its type to be completed, and
it suggests that a belief that guides decisions about the timing of delivery —
namely, that induction of labor at term increases the risk of cesarean delivery
— may not be true after all.”
In summary,the authors concluded “ in women of advanced
maternal age, induction of labor at 39 weeks of gestation, as compared with
expectant management, had no significant effect on the rate of cesarean section
and was not associated with adverse short-term effects on maternal or neonatal
outcomes.”
Currently Dr. Groban is the principal investigator for a
larger trial to test the effects of induction on stillbirth and uncommon
adverse neonatal outcomes. The trial is currently under way within the Maternal–Fetal
Medicine Units Network of the Eunice Kennedy Shriver National Institute of
Child Health and Human Development. This trial, which has a targeted enrollment
of 6000 women, is designed to identify differences in perinatal outcomes among
nulliparous women with uncomplicated singleton pregnancies who are randomly
assigned to induction between 39 weeks 0 days and 39 weeks 4 days of gestation
or to expectant management.
References:
,
, , et al. Randomized trial of labor induction
in women 35 years of age or older. N Engl J Med
2016;374:813-822
.
Life-table analysis of the risk of perinatal death at term and post term in
singleton pregnancies. Am J Obstet Gynecol
2001;184:489-496
