Topic Overview

Full-term babies are delivered
sometime between 37 and 42 weeks of pregnancy. (Those weeks are counted from
the first day of your last menstrual period.) A pregnancy that has
reached 42 or more weeks is called a “post-term” or “post-date” pregnancy. You
might also call it “overdue.” Pregnancy that lasts beyond the due date is
fairly common.

In
most cases, there is no obvious cause of a post-term pregnancy.

Some post-term pregnancies are not truly post-term.
The
due date may not have been figured correctly. (Your due date is 40 completed weeks after
your last period. If you ovulated late in your cycle, your pregnancy didn’t start as
early as this due date says.)

An ultrasound measurement of your fetus during
the first
trimester can give the most accurate due date. But
even that due date is an estimate of when you might deliver.

What concerns are linked to post-term pregnancy?

Most often, a post-term baby is born in good health. But a very small
number of post-term pregnancies are linked to stillbirth and infant death. This is why your doctor or nurse-midwife
will watch you closely after 40 to 41 weeks.

Many doctors and nurse-midwives want to lower risks for the post-term baby by delivering by or
before 42 weeks. In most cases, watching and waiting is also fine. It is often
hard to know which choice is best during the 2 weeks after the due
date:

  • Any time after the due date that a fetal
    problem shows up in testing, it is time to deliver.
  • If the cervix is ready for delivery, many doctors speed up the process by
    inducing labor. This may start in the doctor’s office
    with a simple
    sweeping of the membranes.
  • If the cervix isn’t ready for delivery, watching and waiting is
    a reasonable choice. But giving medicine to soften the cervix and induce
    labor does seem to have some advantages. A review of studies has shown that
    softening the cervix and inducing labor after 41 completed weeks lowers the rate of
    stillbirths and infant deaths (though, either way, deaths are very
    rare).footnote 1

For safety reasons, most health professionals will plan
to deliver a baby by 42 weeks, inducing labor if necessary.

Related Information

References

Citations

  1. Gülmezoglu AM, et al. (2012). Induction of labour for improving birth outcomes for women at or beyond term. Cochrane Database of Systematic Reviews (6).

Credits

ByHealthwise Staff
Primary Medical Reviewer Kathleen Romito, MD – Family Medicine
Adam Husney, MD – Family Medicine
Specialist Medical Reviewer Kirtly Jones, MD – Obstetrics and Gynecology

Current as ofMarch 16, 2017