The first question to consider, of course, is whether your due date is accurate. Often what appears to be a late baby is really only a mistake in calculations; having a baby 9 days "late" is fairly common. The calendar wheel doctors use to calculate your due date is based on counting back 3 months from the first day of your last menstrual period, then adding 7 days. However, these calculations are based on a perfect 28-day menstrual cycle, and very few women have periods that perfect. The reality is that 80 percent of babies arrive between 38 and 42 weeks of pregnancy, so your due date window is much bigger than you might think.
Only about 1 out of every 10 babies is officially overdue, which means that the baby is born after 42 weeks of pregnancy. No one really knows why some babies come early and others come late. Of the many factors that possibly influence pregnancy duration, researchers have found that ethnicity and the number of babies you have play the most important roles. African-American women generally have shorter pregnancies--by three days--than Caucasian women. How many babies a woman has had can also influence gestation time; pregnancies tend to be shorter with each subsequent pregnancy.
If your pregnancy lasts more than 41 weeks, your practitioner will start monitoring your baby's health more closely. She'll probably ask you to do a kick count every day, which means keeping track of your baby's movements. A decline in activity can signal that your baby is ready to exit. Your provider may also do nonstress tests (NST) a couple of times each week to be sure that your baby's heart rate accelerates when he moves. An NST is a painless way of ensuring your baby's health. You'll go to the doctor's office, have a belt with a transmitter placed around your abdomen, and sit comfortably while the fetal heart rate is measured for 20-30 minutes. You may also have an ultrasound to measure amniotic fluid volume or a biophysical profile. The combination of the NST and the ultrasound can provide a host of information on your baby's well-being.
Other than that, the best thing you can do if you're overdue is relax and have fun. Take a walk on the beach, see a funny movie, make love with your partner if your water hasn't broken and your practitioner says it's OK, visit friends, read a book, and store up your energy for delivery day. Most of the time labor happens when it's going to happen. If something you do seems to induce labor, it's probably only a coincidence.
Originally published in You & Your Baby: Pregnancy.
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