A threefold increase in the incidence of placenta previa, from one in 318 deliveries (0.3%) in 1972-1974 to one in 109 deliveries (0.9%) in the twelve-month period ending June 30, 1980, was noted at Vanderbilt University Hospital. Two large groups of patients not present in 1972-1974 were found to be responsible for this increased incidence of placenta previa: one-way maternal transports and women who had had induced first trimester abortions. The frequency of maternal transports having placenta previa was 3.3% (p less than 0.0001), and the frequency of placenta previa in women after an induced first trimester abortion was 3.8% (p less than 0.0001). When correction for maternal transports was made, the endogenous induced first trimester abortion population had a frequency of placenta previa of 2.1% (p less than 0.004), whereas the remainder of the endogenous population had an incidence of placenta previa similar to that found in the years 1972-1974. Induced first trimester abortion is seen as a significant factor predisposing to placenta previa.
PIP: Risk factors associated with the development of placenta previa, a significant complication of pregnancy, are multiparity, advancing age, multifetal gestation, cigarette smoking, and a history of previous abortion. Vanderbilt University Hospital experienced a 3-fold increase in the prevalence of placenta previa, from 1 out of 318 deliveries (0.3%) in 1972-1974 to 1 out of 109 deliveries (o.9%) in the 12-month period ending June 30, 1981. This study retrospectively evaluated the causes for this increase in the frequency of placenta previa. Total number of deliveries, prevalence of placenta previa, maternal age, parity, race, and abortion history were evaluated during the periods 1972-1974 and July 1, 1979 to June 30, 1980. In all cases of placenta previa, the diagnosis was confirmed at the time of Cesarian section. Poisson distribution was used to determine the probability of placenta previa occuring in the various risk groups during 1979-1980, while Chi-square analysis was used to compare frequencies of placenta previa, spontaneous abortion, and induced abortion during the 2 periods. The increased incidence of placenta previa was attributed to 2 large groups of patients not present in 1972-1974: 1-way maternal transports and women who had had induced first trimester abortions. Of 332 maternal transports, 11 (3.3%) had placenta previa (p0.001). Of 210 patients with a history of induced first trimester abortions, 8 (3.8%) had placenta previa (p0.0001). 150 were in their first pregnancy since the induced first trimester abortion, with 7 (4.6%) having placenta previa (p0.001). 4 (2.1%) of 195 nontransport patients who had undergone induced first trimester abortion had placenta previa (p0.0004). Suction curettage was the abortion method performed in 6 of 8 women with placenta previa. Mean time interval between induced first trimester abortion and termination of pregnancy complicated by placenta previa was 42.25 months. Average age and parity of patients was 28.6 years and 1.95 respectively, significantly higher than that of the general population (p0.001). Endometrial curettage may play a role in the increased incidence of placenta previa subsequent to induced first trimester abortion. Limitation of this study is the relatively small sample size. Further research should be done to elucidate the potential risks of induced first trimester abortion.