As the exact trigger that sets off labor is unknown, it's not clear why some women are overdue. You are more likely to be overdue if this is your first baby, if you've had an overdue baby before, or if the condition runs in your family. Some think it's more common in well nourished women, and there is even evidence that pregnancies are longer in the summer than in the winter. If your due date was figured out from an early ultrasound, this gives a more accurate dating of pregnancy than the date of your last menstrual period, and you'll be less likely to be classified as overdue.
After 41 weeks, there is a slightly increased risk to your baby's health that may be due to the reduced efficiency of the placenta. After 42 weeks the risk increases, but is still small. Depending on hospital policy, you will be offered an induction around 41 weeks (see Induction of Labor). The following may also be done.
After 40 weeks, your doctor may do an internal examination to "strip the membranes." She'll insert a gloved finger into the cervix and pull the membranes in a circular pattern. This can soften the cervix and increase the chance of you going into labor by 30 percent in the next 48 hours. It's safe for you and your baby, but can cause cramps and slight bleeding.
Many doctors induce labor by 41 or 42 weeks. If your pregnancy goes beyond 42 weeks and you don't want to be induced, your doctor may offer monitoring with scans to measure the baby's pulse and volume of fluid around the baby; or you may have a NST (see Monitoring During Labor) once or twice a week until labor to pick up any signs that the placenta is failing. If a problem is found, you'll be advised to have a cesarean or an induction of labor.
You might find the physical and mental stress of being pregnant beyond your due date considerable but it can help to know that unless you have a medical condition, being overdue does not significantly increase your health risks. You may worry that your baby will grow too large, causing difficulty in labor, but your baby isn't likely to put on enough weight in the last week or so to make a big difference and most overdue babies have a normal birthweight.
Excerpted from Pregnancy Day by Day.
Copyright ©2009 Dorling Kindersley Limited.
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