A closer look at “term” birth

Of baby brains and reading scores…

When I was in my pediatric residency I was taught that a baby born between 38 and 41 weeks was “full term.” Babies born in that golden four weeks were thought to be one homogeneous group in terms of future development. A baby born at 38 weeks gestation was home free, at least as far as his neurological future went.

Not so fast. A study of more than 100,000 New York children just published in the journal Pediatrics reports that those born at 38 weeks–the low end of the term age bracket–in general don’t perform as well on standardized tests of math and reading in third grade as do children born later in pregnancy.

And not only that:

Each week of increased gestation from 37 to 41 weeks showed an added benefit in both reading and math scores. Further, children born at 37 or 38 weeks performed significantly worse than children born at 39, 40, or 41 weeks, and have a significantly increased relative risk of impaired reading and math skills on standardized school achievement tests.

The brain grows rapidly between 38 and 41 weeks gestation: gray matter increases nearly 50%,  and myelinated white matter triples as the brain increases in complexity. It’s not surprising that being born even two or three weeks early might negatively impact some babies.

The study isn’t perfect, and it’s best to keep in mind that increased risk doesn’t equal inevitablility–the large majority of babies born at 38 weeks will be just fine. Still, researchers in Denmark, Belarus, Switzerland, and Scotland have recently reported findings similar to those in the New York study–all of which supports the growing effort to reduce elective, early labor induction.

Best to leave babies in the womb until nature says it’s time to come out!




Filed under Education, Maternal-child health, Natural childbirth

11 responses to “A closer look at “term” birth

  1. “Liked” this post, but I wish I could “love”. I hope that more studies continue to be done on this subject because I think we have gone too far over the line on trying to control when babies make their appearance. Certain inductions are necessary of course, but elective inductions prior to 41 weeks need to be looked at much more closely. Thanks for posting.


  2. JenB

    Sad article – another way to get Moms to feel bad about their failures? Sometimes a baby is born early and there is nothing you can do about it. .


    • Jen – The last thing I want to do is make mothers feel bad. I certainly don’t think having a premature baby is a failure. Most premature babies grow and develop normally–I know this from personal experience, because I’ve taken care of many of them over the years.

      My main concern is about pregnancies that end in early, unnecessary, elective inductions–this study showed that there is some risk, however small, in being born at 38 weeks compared with 40-41 weeks. As I said in closing the post, the best thing for babies is to stay in the womb until nature says it’s time to be born.


    • Facts don’t make us feel bad, they inform. We need to accept what we cannot control. Facts empower us to make the best choices when we have a choice. My 29 wkr is brilliant. She knew all her numerals by just after 2 years of age. I do not see this as an attack on me or her (and my babies naturally birth one to three weeks early). I see this as information encouraging us to let babies who can stay in longer and be health to stay where they are best served. I wonder if they had factored for bfing vs. formula feeding, how much of a difference that would make as bfing is made to help a developing brain but ffing is the norm for a majority in the US. It would be helpful to those of us who cannot continue our preg to have the information on how we might be able to close the gap (bfing, kangaroo care, etc.) That would be the obvious next step of research.


  3. Pingback: Full Term? « brilliantbirth

  4. Fatima

    I’m interested to see that 41 weeks is considered the high end as opposed to 42. My hospital was happy to allow me to go to 42 weeks and my baby came at 41 weeks 5 days. I’ve also read a study which found that there was no significant benefit to inducing at 41 weeks as opposed to 42 weeks. Do you have a view on this?


    • Fatima – You make a good point about the 41-week cutoff. That was the parameter used in the study I cited, but obviously a lot of healthy pregnancies go longer. Thanks for writing!


  5. Pingback: The Placenta Blog » Blog Archive » What’s A Few Weeks?

  6. Becky

    Hmmm, but there are reductions in perinatal mortality in inducing, as well as reductions in some particular morbidities. It isn’t simply done for kicks. The evidence is clear at 41 weeks, but there is also evidence that inductions from 39 weeks reduce perinatal mortality compared to expectant management.

    See this Cochrane review: http://summaries.cochrane.org/CD004945/induction-of-labour-in-women-with-normal-pregnancies-at-or-beyond-term
    And this thorough review: http://www.ncbi.nlm.nih.gov/books/NBK38683/
    And this new study looks more at inductions before 41 weeks: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3349781/
    And this found improved neonatal outcomes with elective induction: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2888294/

    We do want consider long term issues, and the evidence is clear that induction shouldn’t be done without indication before 39 weeks, but we mustn’t lose sight of why inductions are done at all in the first place. We can’t just assume that we can wait until “nature intends” labor to start, because nature doesn’t care about the survival of individual babies, and we humans do.


    • Becky,
      Thanks for sending along these studies. You’re right, it appears that elective induction (EI, to save on typing…) does make for lower neonatal mortality, but apart from that rather blunt measure (the Cochrane review states that “baby deaths were rare with either policy”) it’s a bit of a mixed morbidity bag.

      Take meconium aspiration, for example.The Caughey study you cited found a decrease in such outcomes as meconium-stained amniotic fluid at 41 weeks with EI, but noted that the effects were “not robust” at lesser gestational ages—including the early elective inductions I’m concerned about. On the other hand, the Stock review found increased NICU admissions with EI at all gestational ages studied. And Cochrane found a reduction in meconium aspiration with EI versus expectant management, but no difference in NICU admissions.

      Finally, the study by Bailit found higher rates of hysterectomies following EI, and concluded with this statement: “Given that the advantages of elective delivery are primarily social or logistical and not medical, an argument could be made not to offer an elective delivery at all given the maternal risks. At minimum, patients should be well informed of the fetal and maternal risks of elective delivery.”

      It’s a complicated issue, obviously. There is a time and place for inductions, and I’m not speaking against that. My point in this post, as with my posts about concerns with long-term child health issues associated with cesareans (asthma, eczema, diabetes and other chronic illnesses), is that a growing body of evidence supports the idea that interventions like early induction and elective cesareans may not be as benign for babies as was once thought.

      Elective inductions aren’t done for kicks, as you say, but they’re often done for convenience. Waiting until “39 weeks or later” to ensure better outcomes isn’t as precise a matter as it sounds. Many hospitals lack the equipment and personnel needed to accurately date a pregnancy.

      Expectant parents should decide about matters like EI in discussion with their maternity care providers, based on the unique features of their own situation. Parents should be aware of all the pros and cons of EI, though, including the “softer” ones like this study of later academic performance.

      Thanks again,
      Mark Sloan


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