Robert Wood Johnson University Hospital


High-Risk Newborns - Postmaturity

What is postmaturity?

The normal length of pregnancy is from 37 to 41 weeks. Postmaturity refers to any baby born after 42 weeks gestation or 294 days past the first day of the mother's last menstrual period. Less than 6 percent of all babies are born at 42 weeks or later. Other terms often used to describe these late births include post-term, postmaturity, prolonged pregnancy, and post-dates pregnancy.

What causes postmaturity?

It is not known why some pregnancies last longer than others. Postmaturity is more likely when a mother has had one or more previous post-term pregnancies. Sometimes a mother's pregnancy due date is miscalculated because she is not sure of her last menstrual period. A miscalculation may mean the baby is born earlier or later than expected.

Why is postmaturity a concern?

Postmature babies are born at the very end, or past, the normal length of pregnancy. The placenta, which supplies babies with the nutrients and oxygen from the mother's circulation, begins to age toward the end of pregnancy, and may not function as efficiently as before. Other concerns include the following:

What are the symptoms of postmaturity?

The following are the most common symptoms of postmaturity. However, each baby may show different symptoms of the condition. Symptoms may include:

Symptoms of postmaturity may resemble other conditions or medical problems. Always consult your baby's doctor for a diagnosis.

How is postmaturity diagnosed?

Postmaturity is usually diagnosed by a combination of assessments, including the following:

Treatment of postmaturity

Specific treatment for postmaturity will be determined by your baby's doctor based on:

In a prolonged pregnancy, testing may be done to check fetal well-being and identify problems. Tests often include ultrasound, nonstress testing (how the fetal heart rate responds to fetal activity), and estimation of the amniotic fluid volume.

The decision to induce labor for post-term pregnancy depends on many factors. During labor, the fetal heart rate may be monitored with an electronic monitor to help identify changes in the heart rate due to low oxygenation. Changes in a baby's condition may require a cesarean delivery.

Special care of the postmature baby may include:

Prevention of postmaturity

Accurate pregnancy due dates can help identify babies at risk for postmaturity. Ultrasound examinations early in pregnancy help establish more accurate dating by measurements taken of the fetus. Ultrasound is also important in evaluating the placenta for signs of aging.

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