Barrett J M, Boehm F H, Killam A P
Am J Obstet Gynecol. 1981 Dec 1;141(7):769-72. doi: 10.1016/0002-9378(81)90702-x.
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.
范德比尔特大学医院发现，前置胎盘的发病率增长了两倍，从1972年至1974年每318例分娩中有1例（0.3%），增至截至1980年6月30日的12个月期间每109例分娩中有1例（0.9%）。研究发现，1972年至1974年不存在的两组大量患者导致了前置胎盘发病率的上升：单向孕产妇转运和孕早期人工流产的女性。发生前置胎盘的孕产妇转运频率为3.3%（p<0.0001），孕早期人工流产后女性发生前置胎盘的频率为3.8%（p<0.0001）。校正孕产妇转运因素后，内源性孕早期人工流产人群前置胎盘的发生率为2.1%（p<0.004），而其余内源性人群前置胎盘的发生率与1972年至1974年的发生率相似。孕早期人工流产被视为前置胎盘的一个重要易感因素。
