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This article reviews fetal death from nongenetic causes, with an emphasis on the appropriate work-up for these disorders.
The death of a formed fetus can be an emotionally devastating pregnancy complication. Developmentally, the embryo becomes a fetus at 9.5 to 10 weeks' gestation. However, the most commonly used definition of stillbirth in the United States is the death of a fetus of at least 20 weeks' gestation.
The stillbirth rate in the United States has decreased slightly over the past 15 years, with a rate of 6.2 per 1,000 live births in 2003.1 This is almost 1 in 160 pregnancies. The decrease in stillbirths has primarily been in fetal deaths after 28 weeks' gestation. Many stillbirths are from genetic causes. These include aneuploidy, syndromes, malformations, and single-gene (including Mendelian) disorders. This article will review fetal death from nongenetic causes, with an emphasis on the appropriate work-up for these disorders.
Studies that are helpful in determining whether infection contributed to stillbirth include fetal autopsy, placental evaluation, and cultures of fetal tissue. A case of group B streptococcus infection with positive cultures in fetal lungs and inflammation in fetal tissues and the placenta is convincing evidence that infection probably caused the fetal death. In contrast, vaginal colonization with group B streptococcus with negative cultures of fetal tissues and no placental inflammation is not good evidence. In the latter case, the positive culture is probably unrelated to the stillbirth.
Numerous other viruses have been associated with sporadic stillbirths (Table 1).2 Coxsackie A and B viruses can cause placental inflammation, myocarditis, hydrops, and death. Other viruses include adenoviruses, echoviruses, enteroviruses, varicella, rubeola (measles), mumps, and rubella. The risk of stillbirth in association with some of these viruses can be vastly reduced with vaccination.
The human immunodeficiency virus may infect the fetus in utero, but rarely causes stillbirth. In contrast, the herpes simplex virus rarely infects, but can cause fetal death.