It is desirable to identify those pregnancies that run an increased risk of abruptio placentae, as this disorder still is associated with a high perinatal mortality. Data were collected from the Swedish nationwide birth registry system on all 894,619 births in Sweden in the period 1973 to 1981. The overall incidence of abruptio placentae was 0.44%, with a perinatal mortality of 20.2% and a cesarean section frequency of 74.6%. The incidence of abruptio placentae was significantly increased in the case of twin birth, male offspring, mothers below 20 years of age, and with every delivery after the second one. A history of abruptio placentae increased the risk of a similar incident in a subsequent pregnancy by 10.2-fold. The frequency of cesarean section in subsequent parturitions remained high (32.1%) even in the absence of reabruptio placentae, thus demonstrating the need to identify further risk groups.