I wanted to write this blog post b/c I remember in my first pregnancy - toward the end - being so afraid (and peeved) when my OB brought up the topic of the possibility of induction. I was heavily influenced at that time with the many opinions I heard about not inducing, and to instead just wait for the babe to come ("there's no time limit," "there's no eviction notice," "don't choose your baby's birthday," etc) - the opinions/advice were by birth professionals I knew, people I trusted. I even repeated the advice to people I knew - people who trusted my opinion as a doula and childbirth educator. (makes me cringe) I have since heard too many stories similar to this story (or met women) whose unfortunate outcomes did not reflect that sentiment I had ingrained in my head: "baby will come when ready and not a moment too soon." Because that isn't true in every case. Even close monitoring does not guarantee complications are not developing (or that they won't develop closer to or during labor). So it left me questioning.... Is there a time when continuing on with a pregnancy becomes riskier than delivering? That's what inspired me to write this.... I was in search of evidence for induction vs spontaneous labor at or beyond 40 weeks.
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If you are approaching 40 weeks of pregnancy, you
might hear your care giver bring up the topic of induction. If you are
wondering why they are hoping the baby will come sooner, rather than later,
this information may be useful to you. I know the idea of induction may be very scary. Perhaps reading evidence behind the recommendation will help you understand your professional care giver’s concern and help you make a more informed decision. Because ultimately, the choice is yours.
First, in October 2013, ACOG redefined what “term pregnancy” means.
A woman who was “full term” previously meant she was anywhere from 37 to 42 weeks. Now, there are new definitions and “full term” is a shorter window.
The
following represent the four new definitions of ‘term’ deliveries:
Early
Term: Between 37 weeks 0 days and 38 weeks 6 days
Full
Term: Between 39 weeks 0 days and 40 weeks 6 days
Late
Term: Between 41 weeks 0 days and 41 weeks 6 days
Postterm:
Between 42 weeks 0 days and beyond
From the study: “Babies
born between 39 weeks 0 days and 40 weeks 6 days gestation have the best health
outcomes, compared with babies born before or after this period. ”
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Here are several studies discussing labor induction vs expectant management (waiting for spontaneous labor). 41 weeks was the
common “cut off” for induction in these studies.
Please note, in the studies you will see the term "expectant management." I was confused by the term initially so I want to add the definition. Expectant management refers to "watch and wait" for spontaneous labor. It is the "hands off" approach; as opposed to induction, which would be considered active management.
From results:
"If deaths
due to congenital abnormality are excluded, no deaths remain in the labour
induction group and seven deaths remain in the no-induction group."
Conclusion: "A
policy of labour induction after 41 completed weeks or later compared to
awaiting spontaneous labour either indefinitely or at least one week is
associated with fewer perinatal deaths. However, the absolute risk is extremely
small. Women should be appropriately counselled on both the relative and
absolute risks."
From the results:
"There was
one perinatal death in the labour induction policy group compared with 13
perinatal deaths in the expectant management group. "
and
"Fewer
babies in the labour induction group had meconium aspiration syndrome (RR 0.50,
95% CI 0.34 to 0.73; eight trials, 2371 infants) compared with a policy of
expectant management. "
Conclusion:
"A policy
of labour induction compared with expectant management is associated with fewer
perinatal deaths and fewer caesarean sections. Some infant morbidities such as
meconium aspiration syndrome were also reduced with a policy of post-term
labour induction although no significant differences in the rate of NICU
admission were seen.However, the absolute risk of perinatal death is small.
Women should be appropriately counselled in order to make an informed choice
between scheduled induction for a post-term pregnancy or monitoring without
induction (or delayed induction)."
This study is about risks of delivery vs expectant
management, and risk of stillbirth. It also took into consideration for those that delivered,
what was the infant mortality rate - infant deaths of babies born alive that
die before they turn one.
Here is a graph from the study:
Keep in mind the orange line is the expectant management group - this is the non-induction group. You can see the risk of stillbirth (red line) steadily rise
from 37-40 weeks. Then increases more dramatically between 40-41 weeks, then
even moreso after 41 weeks.
Results:
The risk of stillbirth at term increases with gestational age from 2.1 per
10,000 ongoing pregnancies at 37 weeks of gestation up to 10.8 per 10,000
ongoing pregnancies at 42 weeks of gestation. At 38 weeks of gestation, the
risk of expectant management carries a similar risk of death as delivery, but
at each later gestational age, the mortality risk of expectant management is
higher than the risk of delivery (39 weeks of gestation: 12.9 compared with 8.8
per 10,000; 40 weeks of gestation: 14.9 compared with 9.5 per 10,000; 41 weeks
of gestation: 17.6 compared with 10.8 per 10,000).
Conclusion:
Infant mortality rates at 39, 40, and 41 weeks of gestation are lower than the
overall mortality risk of expectant management for 1 week.
#4:
This was published in January 2013. It specifically addresses pregnant women
that are 40 years of age and older.
From the release: “Data from these studies show the risk of stillbirth at 39-40
weeks gestation is doubled for women aged 40 years or over, and at 39 weeks
gestation these women (40+ years) have a similar stillbirth risk to women aged
in their late 20s at 41 weeks gestation.”
and
“It is
justifiable for experts to conclude that inducing labour at an earlier stage of
gestation (39-40 weeks) in older mothers (40+ years) could prevent late
stillbirth and any maternal risks of an ongoing pregnancy, without increasing
the number of operative vaginal deliveries or emergency caesarean sections.”
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These are the studies I have found regarding this
issue of induction vs wait for spontaneous labor. As you can see, because of
the increase in stillbirth, especially after 41 weeks, it is no wonder why
induction of labor is often recommended by 41 weeks.
When deciding, it is important to compare evidence for one
option versus evidence for another option. There will be anecdotes of those who went to 41, 42, 43+ weeks that ended
with a healthy mom and baby, with no complications. But there will also be
anecdotes of those who had elective inductions at 37 or 38 weeks that ended
with a healthy mom and baby, with no complications. It does not mean either
route is what the evidence supports as the safest route to go.
If you have any peer reviewed studies you’d like to add regarding this topic, please
feel free to do so in the comments!
Edited 01/11/2013 to add another study:
#5: http://www.ajog.org/article/S0002-9378(08)00558-9/abstract
Results: Compared to infants born at 38, 39, or 40 weeks, those born at 41w0d to 42w6d have a greater odds of neonatal mortality (aOR: 1.34, 95% CI, 1.08-1.65). Subdividing by gestational week, infants delivered at 41w0d to 41w6d showed elevated mortality relative to earlier term births (aOR: 1.37, 95% CI, 1.08-1.73). Additional analyses support this increased neonatal mortality across all normal birthweight categories.
Conclusion: Infants born beyond 41w0d of gestation experience greater neonatal mortality relative to term infants born between 38w0d and 40w6d.
