What Are the Most Common Stillbirth Causes?

These Factors Are Linked to Pregnancy Loss After 20 Weeks

What causes stillbirths? Giving birth to a stillborn baby is every pregnant woman's worst nightmare. When it does happen, it's natural to want to understand why.

Unfortunately, sometimes doctors don't have an answer to this question. One study found that in a quarter of stillbirths, there is no known probable or possible cause, and other studies indicate an even higher percentage of unexplained stillbirths - up to 60 percent.

Stillbirth causes tend to shift depending on gestational age, and unexplained stillbirth is more common late in pregnancy. 

Let's review the most common culprits that can cause pregnancy loss after 20 weeks. 

Chromosomal Abnormalities, Birth Defects and Stillbirths

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Just as chromosomal abnormalities cause the majority of miscarriages, certain chromosomal problems and birth defects can increase the risk that a baby will be stillborn. According to the March of Dimes, birth defects are a factor in about 15 to 20 percent of stillbirths.

Chromosomal abnormalities are usually determined at conception, but birth defects can be caused by environmental influences.

For example, low levels of folic acid - an important nutrient found in fortified grains and leafy green vegetables - can increase the risk of having a baby affected by neural tube defects such as anencephaly, which is incompatible with life.

Intrauterine Growth Restriction

Intrauterine growth restriction (IUGR) is a condition in which the baby is significantly smaller than expected for the number of weeks of pregnancy. In severe cases, this condition can cause stillbirth or increased risk of newborn loss, perhaps due to the baby not getting enough oxygen or other important nutrients.

The mother's health conditions and lifestyle can also increase the risk of intrauterine growth restriction, and doctors screen for these problems during prenatal care. Some specific risk factors are preeclampsia, pregnancy-induced high blood pressure and smoking in pregnancy.

As part of standard prenatal care, doctors closely monitor a baby's growth so they have the best chance to intervene if a baby seems to be at risk. 

Placental Abruption and Other Obstetric Complications

Placental abruption is a condition in which the placenta suddenly separates from the wall of the uterus during pregnancy, while the baby is still in the womb.

This can happen because of maternal health conditions, trauma to the abdomen in later pregnancy or birth defects in the mother's uterus. Certain lifestyle factors, such as smoking or substance abuse, can also increase the risk.

Symptoms of placental abruption include abdominal pain, contractions and vaginal bleeding. Any woman worried about the condition should see a doctor immediately.

Other obstetric complications, such as multiple gestations and preterm birth, are also factors in some stillbirths.  More »

Infections

Certain bacterial and viral infections, including STDs, in a pregnancy can increase the risk of stillbirth. Infections are a factor in 10 to 25 percent of stillbirths. More »

Cord Accidents

Cord accidents during pregnancy, such as a tight knot in the cord or the cord becoming too tightly wrapped around the baby's neck, are rare. However, according to the March of Dimes, random cord accidents play a role in about 15 percent of stillbirths.  More »

Rare Stillbirth Causes

Many other factors can cause a stillbirth, although these cases are rarer. Here are two examples:

  • Abdominal trauma. Accidents in later pregnancy, such as a car accident or falling down stairs, can cause a stillbirth.
  • Pregnancies far past their due date. Studies also show that pregnancies past 42 weeks gestation are at increased risk for stillbirth, perhaps due to the placenta losing its ability to support the baby. Doctors usually recommend inducing labor in these pregnancies for this reason.

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