In 2017, ACOG and the Society for Maternal-Fetal Medicine revised the definitions of what it means to have a “term pregnancy”. Before this change, all births past 37 weeks were lumped together as “term” and it was assumed it was all the same. Evolving research has shown that it is not all the same. The new definitions take into account the late brain and lung development and normalcy of birth past the EDD. The new definitions are:
Preterm: Before 36 6/7 weeks If a labor begins during this time, it is likely that doctors will try and stop it so the baby’s lungs will be more developed at birth. Babies born during this time often need special care in a Neonatal Intensive Care Unit.
Early term: 37 0/7 weeks through 38 6/7 weeks This is prime time for baby’s brain to be developing and for babies to gain the coordination necessary to safely alternate sucking and swallowing during feeding. During this time, if labor begins, it is likely that doctors will let it move forward, and observe the baby carefully to make sure it transitions well. Most babies who are born spontaneously at this time do very well, though some will need extra help transitioning.
Full term: 39 0/7 weeks through 40 6/7 weeks A two week phase where many people go into labor on their own and babies are ready for life outside the womb.
Late term: 41 0/7 weeks through 41 6/7 weeks This is the week when most first time parents will go into labor and deliver. Babies at this stage tend to do just as well as when they are born at full term.
Postterm: 42 0/7 weeks and beyond After 42 weeks, there is concern that the placenta will not function as well as it once did, and many care providers and parents consider induction if the EDD is sure.
This should improve the health of babies in changing the way care providers think about managing pregnancy and birth.
For example, most babies who are born after a spontaneous labor at 37 weeks and 2 days are just fine. So in the past it was assumed that inducing at that same point would be fine, too. Recent research has shown that assumption is false, so thinking as early term as a time when spontaneous labors don’t need to be stopped, but inductions are too soon, means that more of the babies born early term will be more ready for life outside the womb.
Another example is thinking of the late term as a separate time from the risks of post term. Many, many labors begin spontaneously during that week, so it’s a normal time for pregnancy to continue.
It feels like a lot to take in and remember all the new terms, but it is a new way of thinking that can have real benefit for the health of babies.