Characterizing Fetal Hemorrhage in a Perinatal Autopsy Cohort.

Fetal hemorrhage (FH) is an important and difficult cause of death to recognize at perinatal autopsy. Existing literature is restricted to case reports and small case series, and none comprehensively describe both placental and autopsy findings. We sought to characterize fetal and placenta findings where the ultimate cause of death was determined to be FH to aid in the identification of these cases. This is an autopsy series of perinatal deaths with fetomaternal hemorrhage (FMH) and FH into the amnionic sac. We included singleton pregnancies with Kleihauer Betke (KB) testing, and divided cases into 3 groups: FMH with ≥40% of fetal blood volume, FMH ≤39%, and suspected FH into the amnionic sac with negative KB test. We identified 20 cases from 691 perinatal autopsies, 10 with FMH ≥40%, 5 with FMH ≤39%, and 5 suspected FH into the amnionic sac. Cases with FMH≥40% were likely to have a normal placental weight, villous edema, and fetal hydrops. While FH into the amnionic sac was more likely to have a small placenta with disruption/defect of fetal vessels, and less likely to have fetal hydrops. This study describes the differences and similarities between cases with FMH and FH in to the amnionic sac, and highlights the need for careful placenta and fetal autopsy examinations.