AbstractThe incidence of spontaneous abortion after amniocentesis (19 to 28 weeks gestation) in women who have had previous spontaneous abortions is compared with the rate in women who have not had previous spontaneous abortions. The outcome of the pregnancy after amniocentesis and the previous history of spontaneous abortion is reported for 691 pregnancies. The rate of spontaneous abortion after amniocentesis was found to be significantly higher in women who had one or more previous spontaneous abortions, 12/238 (5 per cent), than in women who did not, 6/453 (1.3 per cent). In women who reported two or more previous spontaneous abortions, the rate was 7/81 (8.6 per cent). No statistically significant effect of maternal age or gravidity was detected. The incidence of spontaneous abortion after amniocentesis was greater in the three weeks following the procedure (three for each of the three weeks) than in the subsequent seven weeks (nine for seven weeks).