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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
most cases, there is no obvious cause of a post-term pregnancy.
Some post-term pregnancies are not truly post-term.
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
trimester can give the most accurate due date. But
even that due date is an estimate of when you might deliver.
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
risk increases with each week, up to 10 out of 1,000 post-term pregnancies after
43 weeks.1 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
For safety reasons, most health professionals will plan
to deliver a baby by 42 weeks, inducing labor if necessary.
American College of Obstetricians and Gynecologists
(2004, reaffirmed 2009). Management of postterm pregnancy. ACOG Practice Bulletin No. 55.
Obstetrics and Gynecology, 104(3): 639–646.
Gülmezoglu AM, et al. (2006). Induction of labour for
improving birth outcomes for women at or beyond term. Cochrane Database of Systematic Reviews (4).
November 2, 2011
Sarah Marshall, MD - Family Medicine & Kirtly Jones, MD - Obstetrics and Gynecology
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