Tuesday, January 7, 2014

Induction versus Spontaneous

photo courtesy of drewesque

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.


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. 


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."

#2: http://www.ncbi.nlm.nih.gov/pubmed/22696345 (June 2012 -- I believe this is the updated version of the study above)

From the results:
"There was one perinatal death in the labour induction policy group compared with 13 perinatal deaths in the expectant management group. "


"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. "

"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.


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.


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:

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.


  1. The reason that one document took into account deaths through the first year was because going post term doesn't just affect the stillbirth it -- it also increases the neonatal (first 28 days) and postneonatal infant mortality rate. So, a baby born at 42 or 43 weeks has a higher risk of death the whole first year compared to a baby born at 40 weeks. This isn't often mentioned, but is well established.

    1. Becky - thanks for your reply. Do you have any other studies that demonstrate the increase risk for those born over 42 weeks? I'd love to add them. Also, I will make an edit in my post. Thanks for pointing that out! It was not something I was aware of.

    2. I just found this: http://www.ajog.org/article/S0002-9378(08)00558-9/abstract

    3. This is a study looking at stillbirth, neonatal and postneonatal death that the ACOG pulled data from for their 2004 statement on post term pregnancy. It has graphs indicated the changes in mortality through 43 weeks, I think. http://onlinelibrary.wiley.com/doi/10.1111/j.1471-0528.1998.tb10047.x/pdf

    4. The rates are not huge and the differences aren't huge, but also keep in mind that late term and post term pregnancies also have increasing rates of morbidity as well as mortality. Still, most babies will be OK. If only we had a crystal ball to know which ones won't!

  2. My friends just lost their baby after more than 42 weeks pregnancy. It is heartbreaking. They were so excited to have a natural birth and welcome their baby. Now they are devastated. I saw a picture, and the baby is perfect. Just not alive.

  3. I'm not dismissing the statistical risk of going post-dates, but it's very, very important to establish whether a woman is *really* post-dates.

    I had my second child at 43 weeks and 3 days counting from LMP. *However* (taking into account the times when I had relations with my husband), I knew for a fact that I conceived not 14 days, but at least a month or possibly more after LMP. My cycles were whacky because I was nursing.

    When I tried to tell this to my doctor, all I got was this glassy-eyed look. She just went by the book and wrote down my due date as 40 weeks from LMP, which was just plain wrong.

    Unsurprisingly, I was misdiagnosed with IUGR and got a lot of grief because my baby wasn't growing "properly". I tried to talk and preach and shout that the baby IS growing properly, according to the REAL gestational age, but everybody just dismissed me as if I were an idiot.

    So... should I have agreed to an induction at 41 weeks? Of course not, because I was really only 39 weeks *and possibly even less*. So I waited and went into labor at 43wks3days, had a baby with a perfect weight (just above average) and a perfectly good placenta.

    1. So, counting by the *real* due date, I went into labor at around 41 weeks, which made perfect sense because my first child was also born at 41 weeks.

      It's extremely important that doctors actually *talk* to, not at, their patients, no matter how overworked they are. A woman knows her cycles better than a doctor who is seeing her for the first time. A woman knows when she had sex. If a woman used an ovulation kit, she knows exactly when she ovulated. All those things should be taken into account.

    2. Hi, thank you for your comment.

      Yes, I can certainly see how things like nursing could impact cycles and due dates

      "It's extremely important that doctors actually *talk* to, not at, their patients, no matter how overworked they are."

      YES. Totally agree.

      "A woman knows her cycles better than a doctor who is seeing her for the first time. A woman knows when she had sex."

      Agree.... BUT... not all women are honest and/or forthcoming (which may be for a variety of reasons). And, in the end, OBs are liable. They are the ones who bare responsibility.

      First trimester ultrasounds can help immensely narrow down a due date in cases where there is confusion.


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