In October 2013, the American College of Obstetricians/Gynecologists (ACOG) issued an updated definition for term pregnancies. The updated definitions are significant because they change when pregnancies are classified as “full term.”

Prior to the new definition, a pregnancy was deemed full term from three weeks before to two weeks after a woman’s due date; that is, a full term pregnancy ranged from 37-42 weeks. It was thought that babies born in this window all performed equally well and had the same level of risk for complications.

Based on newer global data, however, we now know that this isn’t the case. Babies born between 39 and 41 weeks have the least amount of complications, whereas babies born earlier and later than that have some increased risks. This is what has led ACOG to adjust their terminology.

Pregnancies should now be defined as follows:

  • Early term: 37 weeks through 38 weeks
  • Full term: 39 weeks through 40 weeks
  • Late term: 41 weeks
  • Postterm: 42 weeks and late

The goal of the new definitions is to help patients and doctors understand that babies who are not yet 39 weeks still have developing and maturation to do—and that is best done in the womb.

Elective deliveries for non-medical reasons, like a doctor going away on vacation or a parent wanting a certain birthday, are not appropriate before the 39-week mark. While that is not a new concept, ACOG hopes that labeling these babies as early term will discourage elective early deliveries.

Reviewed by Dr. Jen Lincoln, December 2018

Takeaways

  • Full term pregnancies used to include babies born at 37-42 weeks gestation.
  • Babies born between 37-39 weeks of pregnancy are now called early term.
  • Babies who are not yet 39 weeks still have developing to do inside the womb.
  • Early term babies should not be delivered unless there is a medical indication.

References

  1. American Congress of Obstetricians/Gynecologists. Committee Opinion #579. Definition of term pregnancy.
  2. Spong CY. Defining “term” pregnancy: recommendations from the Defining “Term” Pregnancy Workgroup. JAMA 2013;309:2445–6.

Comments

  1. I was delivered at least a month early (possibly 6 weeks) via C-section because my mom developed pre-eclampsia. She was a bit scared because my great-aunt died of pre-eclampsia when she was 18, though of course back then medical care wasn’t as advanced, not to mention her doctor was an idiot who insisted she was fine. Thankfully her baby survived (born the day after New Year’s), but she died later on Valentine’s Day, exactly 2 months before her 19th birthday.

    Reply
  2. Both of my babies were delivered early via c-section. I developed high blood pressure with both pregnancies so my doctor felt it was best to take the babies when they did (my first at 38 weeks and my second right at 37 weeks). My second was much smaller. What a difference a week makes.

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  3. I went into labor on my due date! It made me remember that we don’t need to control everything, our bodies know what they are doing!

    Reply

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