Is intrauterine transfusion associated with diminished fetal growth?

Studies in animal models and human pregnancies suggest that severe fetal anemia and/or replacement of fetal with adult blood result in decreased pH, increased base deficit, and hyperlactacidemia. Similar changes have been noted in growth-retarded, nonanemic fetuses, and we therefore hypothesized that isoimmunized fetuses requiring intrauterine transfusions might have diminished growth. We longitudinally studied growth patterns in 17 isoimmunized fetuses by noting biparietal diameter and head and abdominal circumference measurements at each transfusion. The distributions of these measurements above and below the 25th, 50th, and 75th percentiles derived from our general obstetric population were compared at the initial transfusion and the last ultrasonogram performed before delivery. Birth weights also were noted and their distribution around the 25th, 50th, and 75th percentiles was compared to the expected distribution. For each ultrasonographic parameter, the distribution of measurements at the last ultrasonogram before delivery was not significantly different from the distribution at the initial ultrasonogram. The birth weight distribution also was not significantly different than the expected distribution. Thus we were unable to demonstrate slowing of fetal growth in our severely isoimmunized pregnancies.