deliveries occurred in our hospital, including 752 (3%) deliveries of IVF pregnancies.Methods Placenta accreta was only diagnosed when there were histological findings from the placenta associated with the suitable clinical course. Demographic, obstetrical and fertility characteristics of these patients were retrieved from hospital files.Main outcome measure Rates of PA in pregnancies achieved with IVF versus rates of PA in spontaneous pregnancies.Results The rate of PA in the IVF group was 12/752 (16/1000) pregnancies, compared with 30/24 441 (1.2/1000) among spontaneous pregnancies (P < 0.0001; OR 13.2; 95% CI 6.7-25.8). Among the variables examined, parity, rate of caesarean delivery in the index pregnancy, and birthweight differed significantly between IVF and spontaneous pregnancies.Conclusions The odds of developing PA are significantly higher in IVF pregnancies than in spontaneous pregnancies. These differences may stem from differences in the endometrial environment, or from changes to the endometrium wrought by IVF treatment protocols.

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P lacenta accreta (PA) can be a serious obstetric complication leading to severe postpartum hemorrhage that may require peripartum hysterectomy. Previous cesarean delivery is the most common risk factor associated with PA, and the risk of PA increases with the number of prior cesarean deliveries. The incidence of PA varies widely in the medical literature due to differences in the diagnostic criteria used, such as whether diagnosis is based only on clinical factors or also on histologic aspects. Ultrasound and magnetic resonance imaging are used for early prenatal diagnosis of PA, which is important for improving obstetric outcome by allowing for early planning for cesarean delivery and possible hysterectomy, thereby decreasing PA-related complications. The authors of this study had developed a clinical impression that the incidence of PA was higher among women who have undergone in vitro fertilization (IVF) compared with women who have conceived spontaneously. No association between pregnancies resulting from assisted reproductive techniques and PA has previously been reported. This current retrospective chart review examined the association between PA and IVF pregnancies occurring between 2004 and 2009 at the authors' institution.During the 5-year study period, of 25,193 deliveries at the authors' institution, 752 (3%) were IVF pregnancies. When PA was suspected during vaginal or cesarean delivery, the placenta was sent for pathologic studies. Criteria for clinically suspected PA included difficulty with placental separation requiring manual lysis of the placenta and during cesarean section heavy bleeding from the placental bed requiring hemostatic sutures. From placental pathology reports obtained during the study period, 42 cases of histologically confirmed PA were found among suspected cases based on clinical criteria. PA cases were then divided into spontaneous (SP) and IVF pregnancy groups. Pregnancies achieved after treatment with fertility drugs or intrauterine insemination were placed in the SP group. Demographic, obstetric, current pregnancy and delivery data, and fertility characteristics were obtained from patient records. The main outcome measure was the rate of PA in pregnancies achieved by the 2 methods of conception.Thirty SP and 12 IVF cases of clinically suspected PA were confirmed histologically. The overall rate of confirmed PA was 42 of 25,193 or 1.67/1000 deliveries. The rate in the IVF group was 12 of 752 deliveries or 16/1000 compared with a rate of 30/24,441 or 1.2/1000 deliveries in the SP group. The mean age in the IVF and SP groups was 37.8 years and 33.6 years, respectively. Of established risk factors for PA, only parity differed significantly between the groups; it was significantly lower in the IVF group because most of the women were nulliparous. Among women with PA, 5 women in the SP (17%) and 1 in the IVF (8%) group had a previous cesarean delivery. Curettage procedures had been performed in 42% and 33% of women with PA in the IVF and SP groups, respectively. Mean fetal weights...