After the fetus is delivered, the fetus and placenta are examined carefully to determine why the fetus died. An autopsy often is recommended. Even after extensive testing, however, in more than one-third of cases the cause of stillbirth cannot be determined. 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 35 th 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. 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.