Rh isoimmunization related to amniocentesis.

We report on the incidence of Rh isoimmunization after genetic amniocentesis at our institution. In 115 Rh negative women who underwent amniocentesis and subsequently delivered Rh positive infants, there were 4 (3.4%) sensitizations before birth. This was significantly greater than the 1.5% rate of gestational sensitization found in pooled populations of women who did not undergo amniocentesis. We also noted a significant increase in the number of sensitizations that occurred before 28 weeks. The results were consistent with those of previous studies of this issue, and are discussed in relation to current policies for managing Rh negative women who have second trimester amniocentesis.