The average healthy pregnancy is around 40 weeks. Some babies come earlier and others run later. A pregnancy that lasts longer than 42 weeks is called a post-term pregnancy.
Dr. Siobhan Dolan discusses overdue pregnancies in the book Healthy Mom Healthy Baby. Here is an excerpt from the book.
“Although many post-term babies are healthy, some risks do start to increase after 41 to 42 weeks. An overdue pregnancy takes a toll on the placenta, amniotic fluid, and umbilical cord. As the baby grows larger, the chances of stillbirth and delivery injuries go up, and there is a greater likelihood that the baby will experience meconium aspiration (inhaling stool from the amniotic fluid into the lungs) or a condition called dysmaturity syndrome (in which the baby is no longer getting enough nourishment because the placenta is aging and becoming calcified).
“When a baby is overdue, the provider may do some tests to check on the baby’s health. They include:
– Ultrasound exam
– Kick count, which is a count of how many times your baby moves or kicks you during a certain period of time
– Nonstress test, in which a fetal monitor measures your baby’s heart rate for a certain amount of time
– Biophysical profile, which uses a fetal monitor and an ultrasound to score a baby on each of five factors (nonstress test, body movements, breathing movements, muscle tone, and the amount of amniotic fluid)
– Contraction stress test, which compares your baby’s heart rate at rest with the heart rate during contractions induced by a shot of oxytocin or nipple stimulation
“If these tests suggest that your baby is in good condition, you can continue to wait for labor to begin naturally. If they raise concerns, your provider may wish to induce labor or perform a c-section. Providers rarely allow a pregnancy to go beyond 42 weeks.”