What Are the Most Common Stillbirth Causes?

Giving birth to a stillborn baby is a fear of many pregnant women. When it does happen, it's natural to want to understand what caused the stillbirth. Unfortunately, sometimes doctors don't have an answer to this question. One study found that in approximately one-quarter of stillbirths, there is no known probable or possible cause.

A stillbirth is a fetal loss that happens after 20 weeks of pregnancy. A fetal loss before 20 weeks is typically referred to as a miscarriage. Stillbirths can be further categorized as early (20 to 27 completed weeks), late (28 to 36 completed weeks) or term (37 weeks or more). The cause of stillbirths can vary based on gestational age and underlying risk factors. Review the most common causes of pregnancy loss after 20 weeks. 

Chromosomal Abnormalities and Birth Defects in 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. Chromosomal abnormalities, especially those associated with anatomic abnormalities or birth defects, account for a higher percentage of stillbirths.

According to the March of Dimes, birth defects are a factor in about 14% of stillbirths.

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 structural abnormalities 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 pregnant woman experiencing these symptoms should see a doctor immediately.

Other obstetric complications, such as multiple gestations and low amniotic fluid, are also factors in some stillbirths. 


Certain bacterial and viral infections, including sexually transmitted diseases (STDs), can increase the risk of stillbirth. Infections are a factor in 10% to 20% of stillbirths.

Umbilical 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 10% of stillbirths.

Pregnancies Far Past Due Date

Studies 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 at or before 42 weeks gestation for this reason.

Maternal Medical Problems

Several maternal medical conditions are associated with an increased risk of stillbirth. This could be a condition that a woman had before she became pregnant or one that she has developed during her pregnancy. Some examples are:

  • Hypertension
  • Diabetes
  • Autoimmune conditions like lupus
  • Certain blood clotting disorders
  • Obesity

If your pregnancy is complicated by any of these conditions, your doctor may recommend additional testing and/or delivery before your due date.

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