Feto-maternal haemorrhage associated with genetic amniocentesis: results of a randomized trial.

Maternal serum alpha-fetoprotein (AFP) levels were determined before and after genetic amniocentesis (n = 283) or ultrasound scan (n = 268) in a group of women participating in a randomized trial of genetic amniocentesis. Increases in AFP levels were seen significantly more often after amniocentesis than after ultrasound scan (P less than 0.001) and 48 women in the amniocentesis group had increases in AFP (delta AFP) that were larger than the maximum delta AFP (+/- 25 micrograms/l) seen in the ultrasound group. If a delta AFP of greater than 25 micrograms/l represents a feto-maternal haemorrhage (FMH) attributable to amniocentesis, the rate of amniocentesis-induced FMH was 17%. Such FMH was seen significantly more often after transplacental amniocentesis or after amniocentesis performed by less experienced operators. No association was detected between birthweight and FMH attributable to amniocentesis.