Ultrasound is now well established as a noninvasive diagnostic modality in the detection of obstetric abnormalities. Its use in the detection of fetal anomalies has involved primarily anencephaly, microcephaly, and hydrocephaly (1, 2, 3). A previous report compared the usefulness of ultrasonic B scanning and conventional radiography in demonstrating fetal ascites in hydrops fetalis (4). This report concerns an additional case where the ultrasound examination was instrumental in the detection of a hydropic fetus in an Rh-isoimmunized woman.
CASE REPORT
S. H. is a 27 year old gravida 3, para 2, Caucasian female with known Rh isoimmunization. Her first pregnancy produced a normal, healthy female who was Rh positive. Seven years prior to this admission, the patient was in an auto accident and suffered m u l t i n l ~ fractures. She received five units of blood at that time. The blood type of these transfusions is unknown. Six years prior to this admission, she delivered an erythroblastotic infant which died three hours after a term delivery. The patient was followed closely during the present pregnancy because of her known Rh isoimmunization.
The patient had her first ultrasound examination at the Los Angeles County-USC Medical Center at approximately 27 weeks' gestational age; she was asympatomatic at that time. The ultrasound examination at that time demonstrated an abnormally thick placenta (Fig. ). The single fetus was in the cephalic position. The biparietal diameter was 7.1 cm, which corresponds to a mean gestational age' of approximately 28 weeks. No definite thickening of the fetal scalp was seen. The fetal abdomen was distended, and