Fetal-maternal bleeding associated with genetic amniocentesis.

Maternal serum alpha-fetoprotein (AFP) elevation following midtrimester genetic amniocentesis (post-AFP) was studied as an indicator of fetal-to-maternal bleeding (FMB). A post-AFP elevation was observed in 28 of 333 (8.4%) consecutive patients who before the procedure had preliminary placental localization by ultrasound and a normal serum AFP concentration (pre-AFP) for the gestational age. The absolute elevations of post-AFP and serial AFPs and the correlation with placental localization all suggest that this is related to FMB. The frequency of spontaneous abortion in patients with an elevation of post-AFP (4 of 28 cases, 14.29%) as opposed to the frequency of those patients who did not demonstrate this phenomenon (3 of 305, 0.98%) was significantly different. The higher frequency of anterior placental implantations in the former group suggests that preliminary placental localization by ultrasound may be important when counseling the patient concerning the risk of amniocentesis. The implications of these findings regarding Rh sensitization and the need for Rh immunoglobulin prophylaxis following this procedure are discussed.