Learn about the risks of being overdue and the monitoring methods available.

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Why Are Some Women Overdue?

Full-term pregnancies range from 38 to 42 weeks. But what if your pregnancy continues beyond 42 weeks? It's not unheard of -- in fact, according to the American College of Obstetricians and Gynecologists, 10 percent of all pregnancies go past 42 weeks. But why is the process longer for some?

    Some pregnancies are post-term. But as it turns out, others are actually the result of the incorrect assignment of a due date. Due dates are tricky because it's hard to pinpoint the exact age of a fetus. Reasons for this include irregular periods, sketchy or inaccurate menstrual history presented to the obstetrician, and mistaking spotting during very early pregnancy for a period. Doctors usually use several methods together to make their best estimate of a due date, including:

      • Calculation based on your last ovulation (the most reliable method).
      • Calculation based on the first day of your last menstrual period.
      • Clinical examination of the uterus for size.
      • Your first detection of fetal movement (the fetus usually makes its first movements between 16 and 20 weeks).
      • Fetal heartbeat (in normal pregnancies, the doctor can detect it between 18 and 20 weeks).
      • Ultrasound, which during early pregnancy can estimate fetal age within seven to 10 days (it's not as effective later in the pregnancy).

        Unfortunately, if you have irregular cycles it could prove difficult to accurately predict a due date.

          What Are the Risks?

          According to the ACOG, 95 percent of babies born between 42 and 44 weeks are born safely. But going past the due date does carry some risks, including:

            • The placenta's ability to provide baby with adequate oxygen and nutrients may be compromised.
            • The volume of essential amniotic fluid may decline as baby grows (this increases the possibility of a pinched umbilical cord).
            • The possibility of fetal distress increases.
            • The baby could grow too large to pass safely through the birth canal (also known as macrosomia).

              With post-term pregnancies, there's also an increased possibility that the baby could have a bowel movement while still in the womb, putting him in danger of inhaling the waste product known as meconium.

              Some of these complications can lead to a cesarean delivery which, as a surgical procedure, carries its own risks.

                How Is a Baby's Condition Assessed?

                Luckily, there are methods that your physician can use to monitor your post-term baby's condition. Among these methods are:

                  • Kick count: A "kick count" is a record you keep of how often your baby moves. Your doctor will tell you to contact him immediately should you notice your baby suddenly decreases his movements. This could be a sign of fetal distress, which would require immediate testing to determine your baby's condition to asses whether delivery should be initiated quickly.
                  • Nonstress test: This test, a type of electronic fetal monitoring, uses a special instrument to measure how your baby's heart reacts when his body moves. This helps the doctor determine if your baby is in distress.
                  • Contraction stress test: When your uterus contracts, this test (which is another form of electronic fetal monitoring) measures your baby's heart rate with a special instrument. It helps determine your baby's condition during labor, and allows your doctor to see if there's any fetal distress.
                  • Ultrasound: Your doctor can determine your baby's size, position, breathing rate, heartbeat, and body movements with an ultrasound. Ultrasound is also useful in determining how much amniotic fluid surrounds your baby. This is important to determine because insufficient amniotic fluid for prolonged periods can cause labor complications. In addition, your doctor can assess the size and position of the placenta using ultrasound. This information is important for your doctor to know because the placenta provides your baby with life-sustaining oxygen.

                    Will My Doctor Induce Labor?

                    Depending on your condition, and that of your baby, your doctor may discuss the possibility of inducing labor. This is a decision that must be made on a case-by-case basis. Remember that most babies are not born on their actual due date. While complications could potentially occur in a postdate pregnancy, they're rare. Most of the time, babies are born healthy and complications are minimal. This is the result of the excellent fetal monitoring techniques available to your health-care provider.

                    While you might feel uncomfortable and anxious to meet your new baby, rest assured that a postdate pregnancy is not uncommon. Keep the lines of communication open with your health-care provider. It might help to write down your questions so you can discuss them at your visits. She can inform and reassure as she monitors your progress.

                    Source: American College of Obstetricians and Gynecologists

                    All content here, including advice from doctors and other health professionals, should be considered as opinion only. Always seek the direct advice of your own doctor in connection with any questions or issues you may have regarding your own health or the health of others.