Etiology The main risk factor for placenta accreta is Prior uterine surgery In the US, placenta accreta most commonly occurs in women who Have placenta previa and have had a cesarean delivery in a previous pregnancy Incidence of placenta accreta has been increasing; it occurred in about 1/30, 000 in the 1950s 1/500 to 2000 in the 1980s and 1990s 3/1000 by the 2000s In the US between 1998 and 2011, 1 in 272 (1) In women who have placenta previa, the risk of placenta accreta increases from about 10% if they have had one cesarean delivery to > 60% if they have had > 4 cesarean deliveries.