Passing the due date - what happens?

When your due date arrives, you will be more than ready to have your baby! Most women deliver the baby somewhere between 37 and 42 weeks. According to the American College of Obstetricians and Gynecologists, only 5% of babies arrive on the exact due date. Approximately 10% of babies are not delivered by 42 weeks, and when that happens, it is referred to as a "post-term pregnancy."

Why Does This Happen?

The most common cause of post-term pregnancy is that your due date was miscalculated and you really are not overdue, but right on time. Only about 2% of pregnancies are really post-term. The reasons for having a true post-term pregnancy are unclear, and there is no definitive answer as to why it happens. The most important aspect of diagnosing a post-term pregnancy is knowing the gestational age of the baby.

What Are The Risks?

If you have still not delivered at 42 weeks, there are increased risks to your health and to the health of the baby. As the baby gets closer to full term, the placenta, which is the link between you and the baby, may stop working as effectively as it had before. This could influence the oxygen and nutrients that the baby receives from you. As the baby continues to grow, the amount of amniotic fluid or water surrounding the baby may lessen. When this happens the umbilical cord may get compressed when the baby moves or by uterine contractions. This can also interfere with the baby's ability to receive the appropriate amounts of nutrients and oxygen.

The increased risks to the baby include:

• Dysmaturity (post-maturity) syndrome: The baby has long fingernails and hair, a long and lean body, and wrinkled or parchment-like skin.
• Fetal distress: the baby is not receiving enough oxygen, causing an abnormal heart rate or other problems.
• Meconium aspiration: the baby may have a bowel movement into the amniotic fluid and then inhale it into its lungs. This could cause the baby to get pneumonia, but often a baby with meconium staining will do fine.
• Macrosomia: the baby grows too big, and this makes it harder to deliver vaginally through the birth canal.

What Will Happen?

If you reach 41-42 weeks or a point where the doctor feels it is important to check the well being of the baby, there are some tests that can be done. The tests include fetal monitoring (including non-stress test or biophysical profile) and ultrasound. If these tests show that the baby is active and healthy and the amniotic fluid volume is normal, the doctor may decide to continue monitoring at scheduled intervals until your labor starts naturally.

If some of the tests show that the baby might be having problems, the doctor will decide whether you and the baby can tolerate induced labor (labor brought on with the help of medications; either vaginal suppositories to ripen the cervix or IV medication) or whether the baby needs to be delivered by C-section.

You will be in close contact with your doctor at this time until your delivery. If the decision made is to induce labor, you will be monitored continuously. If any problems occur during labor, a C-section delivery will be done immediately.

While there are risks associated with post-term pregnancy that will require your baby to get special care after birth, there are also many post-term babies who are born healthy without any complications. The monitoring and tests that are currently available for post-term pregnancies has helped to increase the likelihood of good outcomes.

Review Date: June 29, 2001
Reviewed By: Peter Chen, M.D., Obstetrics and Gynecology, University of Pennsylvania School of Medicine. Review provided by VeriMed Healthcare Network.

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