Post-term Pregnancy Causes and Risks

Post-term pregnancy is a pregnancy that lasts longer than 42 weeks.  That is two weeks past the normal 40-week gestation period.  Since a post-term pregnancy is linked with both fetal and maternal health complications, doctors usually do everything they can to ensure that an infant is delivered as close to the due date as possible.  In some cases that means inducing labor, which comes with its own set of risks.

post-term pregnancy causes and risk. Neonatal baby in hospital.

Post-term Pregnancy Causes

In many cases, post-term pregnancy is a matter of miscalculating the date of conception.  Yet, physicians should always perform an ultrasound during the first half of the pregnancy to promote accuracy.  Although there is never a guarantee of an infant’s due date, an early ultrasound will give a better idea of the due date.

Aside from miscalculating the date, other factors that may contribute to post-term pregnancy include:

  • Previous post-term pregnancies
  • Maternal obesity
  • Sulfatase deficiency in the placenta
  • Central nervous system abnormalities
  • Anencephaly

Post-term Pregnancy Risks

According to the American Academy of Family Physicians (AAFP), there are numerous dangerous health risks associated with post-term pregnancy, including:

Fetal Macrosomia

Fetal macrosomia refers to an infant who is over 8 pounds, 13 ounces at birth.  This may cause childhood diabetes, obesity and metabolic syndrome.  Mothers are also as risk when delivering a large baby, including uterine rupture, genital lacerations and excessive bleeding after delivery.

Placental Insufficiency

Placental insufficiency, also known as uteroplacental vascular insufficiency, occurs when the placenta fails to deliver adequate oxygen and nutrients to the infant.  This can occur due to a small placenta, or because the placenta is not functioning properly. After 37 weeks of pregnancy, the placenta reaches its maximum size and its functions begin to reduce. The longer an infant goes without proper nutrition and oxygen, the more at risk they become for a host of health problems.  Some possible health problems include oxygen deprivation at birth which can lead to cerebral palsy and learning disorders.  Since the placental cord may compress in post-term pregnancies, there is a heightened risk of placental insufficiency. 

Meconium Aspiration

Meconium aspiration is marked by an infant breathing in amniotic fluid and meconium (newborn feces) shortly after birth.  Infants who are born post-term are more likely to have a bowel movement while still in utero.  Meconium aspiration is extremely dangerous and can lead to oxygen deprivation, lung inflammation and lung infection.  Although rare, it can also lead to persistent pulmonary hypertension of the newborn (PPHN) and permanent brain damage.

Risks to Mothers

Mothers are also at risk for developing dangerous medical issues, including postpartum hemorrhaging, bacterial infections, perineum injuries and a chance of requiring a cesarean section (C-Section) surgery.

Post-term Pregnancy Treatment

Treatment is imperative for post-term pregnancy and if done properly, may help prevent many of the aforementioned risks.  Typical treatment options may include:

  •  Antenatal Fetal Monitoring: An infant may be monitored closely once the due date passes in order to detect any signs of distress.  AAFP doesn’t recommend antenatal fetal monitoring until the 42nd week pregnancy.
  • Contraction Stress Test: A contraction stress test will provide Oxycontin to the mother in an attempt to start contractions.  Doctors generally prescribe the medication for intravenous use.
  • Biophysical Profile: A biophysical profile (BPP) is a test that will determine an infant’s overall physical score in regards to movement, breathing, fetal tone and the volume of amniotic fluid.  
  • Labor Induction: It’s often difficult to determine the best time to induce labor, but if the results of the previously mentioned treatment options indicate fetal distress, physicians will normally induce labor.  Labor induction can include a scheduled C-section or medication applied to the cervix that promotes contractions.

It’s important to note that labor induction comes with its own health risks.  These include low fetal heart rate, excessive maternal bleeding and umbilical cord problems.  However, in most cases, labor induction greatly outweighs the risks of allowing the pregnancy to continue if the infant is in distress.

Birth Injury Guide

Written By BIG Staff

The team at Birth Injury Guide is comprised of lawyers, doctors, nurses and professional writers. We strive to provide up-to-date content that is accurate and relevant to the needs of families affected by birth injuries.