The unreliability of amniotic fluid bilirubin measurements in isoimmunized pregnancies in sickle cell disease patients.

Amniotic fluid spectrophotometric analysis for bilirubin (delta optical density [delta OD450], at 450 nm) is used to assess the severity of fetal involvement in isoimmunized pregnancies. Two patients presented with sickle cell anemia and hyperbilirubinemia who also were isoimmunized. The first patient had anti-kell and anti-e antibodies, whereas the second patient had anti-Lewisa and anti-Coltonb antibodies. Delta OD450 was elevated in both patients. The difficulty in interpretation of high delta OD450 in the presence of maternal hyperbilirubinemia is stressed. Sickle cell diseased patients are particularly prone to present with this problem. These patients always have hyperbilirubinemia and a relatively high incidence of irregular antibodies because of the numerous blood transfusions they receive. The management of these two patients is presented with suggestions for the use of alternative modalities of monitoring isoimmunized pregnancies in patients with hyperbilirubinemia.