What causes a Stillbirth?

The most common known causes for stillbirth include:

Placental problems - Placental abruption, a condition in which the placenta peels away, partly to almost completely, from the uterine wall before delivery, most commonly occurs around the 35th week of pregnancy. It results in heavy bleeding that can threaten the life of mother and baby, and deprives the fetus of adequate oxygen, sometimes resulting in fetal death. Placental abruption is diagnosed with an ultrasound examination. Women who smoke cigarettes have a 50 percent greater risk of abruption than nonsmokers, while women who use cocaine during pregnancy may at least double their risk. Women who develop a pregnancy-related form of high blood pressure (preeclampsia) also have twice the risk of abruption as unaffected women. Other problems with the placenta, which prevent it from supplying the fetus with enough oxygen and nutrients, also contribute to fetal death.

Birth defects - Between 5 and 10 percent of stillborn babies have abnormalities involving their chromosomes, the tiny thread-like structures in each cell that carry our genes. Chromosomal abnormalities are the most common cause of miscarriages that occur before 20 weeks of pregnancy, and they also can cause fetal death at any time during pregnancy. Other stillborn babies have structural malformations that are not caused by chromosomal abnormalities, but can result from genetic, environmental or unknown causes.

Growth restriction - Fetuses who are lagging in growth are at increased risk of death from asphyxia (lack of oxygen) both before and during birth, and from unknown causes. Women with high blood pressure are at increased risk of having a growth-retarded baby. An ultrasound examination during pregnancy can show that the fetus is growing poorly, allowing the pregnancy to be monitored carefully.

Infections - Bacterial infections involving the fetus or placenta are an important cause of fetal deaths that occur between 24 and 27 weeks of gestation. These infections often cause no symptoms in the pregnant woman, and may go undiagnosed until they cause serious complications, such as fetal death or preterm birth (before 37 completed weeks of pregnancy). After delivery, tests on the placenta can show whether or not a bacterial infection caused the death.

Doctors once believed that lack of oxygen (asphyxia) during a difficult delivery caused most stillbirths. While asphyxia during delivery still causes fetal deaths, it is an uncommon cause of these losses.

Other infrequent causes of stillbirth include: umbilical cord accidents, trauma, maternal diabetes and high blood pressure, and postdate pregnancy (a pregnancy that lasts longer than 42 weeks).

Learning the cause of a stillbirth can help a couple cope with their devastating situation. When the cause of a stillbirth is known, health care providers are better able to counsel the couple about the risk of stillbirth occurring again in another pregnancy. For most couples, the risk will be low. For example, chromosomal abnormalities or cord accidents are unlikely to recur in another pregnancy. However, if the stillbirth is due to a chronic maternal illness (such as systemic lupus erythematosus or high blood pressure) or if the stillbirth is due to a genetic disorder, the couple may face a higher risk of recurrence. In such cases, the couple would benefit from genetic counseling. A genetic counselor can advise the couple about the risk of stillbirth or other adverse pregnancy outcomes happening again in another pregnancy.

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