Transplacental fetal hemorrhage after amniocentesis.

A retrospective survey of Winnipeg Rh laboratory data from January 1, 1981 to December 31, 1984 determined that, despite placental localization, 2.6% of 974 women having amniocenteses performed at 16 to 18 weeks' gestation for genetic reasons and 2.3% of 1215 women having amniocenteses performed between 32 and 38 weeks' gestation had fetal-maternal transplacental hemorrhages greater than or equal to 0.1 mL of fetal red cells due to placental trauma. In 1.6 and 1.8%, respectively, the fetal transplacental hemorrhages were greater than or equal to 1 mL. Four of 99 alloimmunized women undergoing 257 amniocenteses for determination of severity of fetal erythroblastosis had fetal transplacental hemorrhages all greater than 5 mL of fetal red cells. The 1.9% incidence of fetal transplacental hemorrhages after amniocentesis in alloimmunized women is 83% less than the 11.2% incidence that occurred in the authors' institution from February 1963 to December 1966. However, in three of the four women, there was a very rapid rise in Rh antibody titer and increased severity of Rh fetal disease. Only the alloimmunized woman who meets strict criteria, indicating that her fetus is at risk of fetal death, should be subjected to amniocentesis, and then only after careful placental localization by ultrasound. Because fetal transplacental hemorrhages occur after amniocentesis despite ultrasound placental localization, 300 micrograms of Rh immune globulin should be administered to all unimmunized Rh negative women after amniocentesis.