Three cases of massive fetomaternal hemorrhage presenting without clinical suspicion.

Fetomaternal hemorrhage (FMH) is a common obstetrical occurrence most often associated with small volumes of blood transferred across the placenta. Fetomaternal hemorrhage leads to alloimmunization of Rh D-negative mothers, resulting in an increased risk of hemolytic disease of the newborn. Massive FMH involving volumes of blood greater than 30 mL can cause substantial fetal morbidity and mortality. Massive FMH may present with signs and symptoms such as decreased movement, sinusoidal heart rhythms, or fetal anomalies. We present 3 cases of clinically unexpected massive FMH of 206, 88, and 155 mL. The treating clinicians were unaware of any fetal or maternal signs or symptoms of FMH until contacted by the laboratory. These cases illustrate the necessity for FMH quantitation, even in the absence of clinical suspicion. Additional studies are needed to find better ways to identify these patients in advance. Development of criteria allowing identification of patients at risk would be of benefit to both mother and baby.