How Doctors Now Define Full-Term Pregnancy

Learn what's considered an early-term, full-term, late-term and post-term pregnancy.
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May 5, 2017
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Not sure what a “full-term” pregnancy looks like anymore? Chances are, you’re not alone. To clear things up, doctors and scientists came together in 2013 to redefine what the next nine months of your life will look like, how long baby needs to develop, and just what it means when you deliver too early—or too late.

Teams from the American College of Obstetricians and Gynecologists’ (ACOG) Committee on Obstetric Practice, the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine (SMFM) have created term guidelines for pregnancy and published the opinion-findings in the journal Obstetrics & Gynecology.

Traditionally, term pregnancy only referred to the three weeks before and the two weeks following your estimated due date, but now, as research continues to show that baby’s physical and mental faculties are affected when they’re born during that time frame, researchers note the importance those five weeks are to development.

So, as a means to combat the issue and provide clearer definitions, OBs, doctors and scientists created four new categories to help define term pregnancies. Dr. Jeffrey L. Ecker, chair of the ACOG Committee on Obstetric Practice and the Society for Maternal-Free Medicine, said, “We wanted there to be no confusion among providers or patients [who assume] that outcomes were uniform between 37 and 42 weeks. We are concerned that by applying a single label to them—the label of ‘term’—some might come to that conclusion.” The categories are as follows:

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

Post-term: Between 42 weeks, 0 days and beyond

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“Increasingly it has been demonstrated in good studies with good research that outcomes between 37 to 39 weeks, for example, are different and worse than outcomes between 39 and 41 weeks,” Ecker added. So, what exactly do those adverse outcomes look like?

Researchers found that children born at 37 and 38 weeks had significantly lower reading scores when compared to their same-age peers who were born at 39, 40 and even 41 weeks. They also found that math scores for children born at 37 and 38 weeks were also lower. Kids that get too early of a start on life are more likely to struggle than their peers who had full-term pregnancies. A few months later, researchers in Buffalo found that babies born at 37 and 38 weeks (early-term babies), were physiologically immature when compared to their full-term peers.

With the help of these term-guidelines, the ACOG feels that moms-to-be will have a clearer picture of just how quickly baby is developing and just how important those final weeks are. Patients know that due date," says Dr. Mari-Paule Thiet, the director of the Division of Maternal-Fetal Medicine at the University of California, San Francisco. “They circle it and they know the exact date that that baby should come. In the past we gave that gray zone of five weeks for it to come and said it could come any time within that window, and it’s all the same.” In short, Thiet feels that these definitions will give moms a more realistic idea of when it’s time for them to deliver. She adds, “I think it’s good that now patients can think, ‘ok, this is really my two weeks until due date week. I might deliver before my due date, but I hope I don’t.’”

The guidelines aren’t just a big help to pregnant women. Ecker hopes that the new four-stage term definition will help doctors and scientists understand the effects of delivery-time. The research is invaluable for OBGYNs treating moms-to-be. “Because we do recognize that outcomes are different, by adding specific labels, it allows doctors and patients to speak specifically about what they anticipate, and for the language used to be consistent among different doctors and practices so that everyone will apply ‘early term’ to 37 to 39 weeks instead of one hospital saying, ‘early term’ and another hospital saying ‘short of term.’ Everyone will speak the same language.”

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