Post-term Pregnancy Causes and Risks

A woman may experience preterm delivery, but there is also a risk for post-term pregnancy. Post-term pregnancy is a pregnancy that has gone beyond the expected 42 weeks of typical gestation. Generally, pregnancy is thought to last between 40 and 42 weeks, and if it extends beyond this point it will be labeled as post-term.

Many people are confused and wonder just why a pregnancy that lasts a little longer than normal might be considered a problem. While everyone assumes a mother is going to be more than ready to deliver by the time the ninth month of pregnancy comes to an end, if the baby requires more time to develop it should not be a problem. However, it is rare that a post-term pregnancy occurs for health reasons, and the outcome of such a lengthy pregnancy can be harmful to the mother and baby.

What Causes This Issue?

Why would someone have an overly long pregnancy? Actually, one of the main reasons that it is believed a woman is experiencing a post-term pregnancy is because the date of conception was calculated incorrectly. In other words, human error may make her believe she is due when she is not. However, there are actual medical factors that can cause this condition to develop too. They include:

  • Maternal obesity
  • Abnormalities in the mother’s central nervous system
  • Previous pregnancies that went post-term
  • Deficiency in the placenta of sulfatase enzyme
  • Anencephaly (a malformation of the skull of the baby)
  • Placental insufficiency

The last item, placental insufficiency, can be a factor causing an overly long pregnancy, but it is also one of the key risks too. This is because by the time a woman has reached 37 weeks of pregnancy, the placenta is unable to grow any farther, and actually stops working as effectively. This can cause a baby to begin to experience oxygen and nutrient deprivation the longer they remain in utero.

What Problems Can Post-term Pregnancy Cause?

This tells us that post-term pregnancy can also cause a host of problems for the baby. The issue of placental insufficiency is one, and this can lead to conditions such as cerebral palsy, cognitive and developmental disorders, and brain damage. It can also lead to an overgrowth of the baby known as fetal macrosomia. This is when a baby is born at a weight more than 8 pounds 13 ounces, and which puts that baby at risk for lifelong metabolic issues and even diabetes.

There is also a risk of meconium aspiration syndrome. This is when a baby defecates before birth and then inhales the material. It can lead to oxygen deprivation and infection of the lungs. These too can cause brain damage and birth injury.

Mothers are also at risk at such times. The baby with fetal macrosomia may be unable to be delivered naturally, and if a mother does not get a cesarean section she could be at risk for uterine rupture or excessive bleeding. Post-term pregnancy also puts a mother at risk for infection, perineum injury, and the need for an emergency c-section.

Detecting Issues

Regular medical exams will indicate if a baby is developing properly or if there are some issues of concern. Ultrasounds can determine the approximate development of the baby, and if further treatments are deemed necessary, physicians can take a host of steps that include:

  • Inducing labor
  • Monitoring the baby
  • Performing contraction stress tests
  • Conducting a biophysical profile on the baby

Each of these things will provide the physician or medical team with a clearer idea of just what is going on and how to keep the mother and baby safe.


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