Ultrasonographic fetal surveillance in the management of the isoimmunized pregnancy.
During the past 20 years the management of pregnancies involving rhesus sensitization has been based on determinations of the optical density of amniotic fluid as an index of the bilirubin concentration and the degree of hemolysis. High values have dictated intervention in the form of delivery or intrauterine transfusion, depending on the gestational age. Since 1982 intensive surveillance with ultrasound imaging and electronic monitoring of the fetal heart rate have become useful in decisions about the timing of intervention. Using these tools, we followed 11 fetuses who would previously have been treated by multiple intrauterine transfusions or early delivery, for 8 to 63 days without treatment. All were born alive, in good condition and without hydrops, at gestational ages of 30.5 to 36.0 weeks. The lengths of stay for the neonates ranged from 8 to 48 days, and all were discharged alive. We conclude that rhesus sensitization in a select group of fetuses, who according to former standards would have been candidates for earlier delivery or intrauterine transfusion, can be managed expectantly for longer periods by careful observation with modern techniques of surveillance.