Objective: To explore the association between cryopreserved embryo transfer (CET) and risk of placenta accreta among patients utilizing in vitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI).

Design: Case-control study.

Setting: Academic medical center.

Patient(s): All patients using IVF and/or ICSI, with autologous or donor oocytes, undergoing fresh or cryopreserved transfer, who delivered a live-born fetus at ≥24 weeks of gestation at our center, from 2005 to 2011 (n = 1,571), were reviewed for placenta accreta at delivery.

Intervention(s): Cases of accreta (n = 50) were matched by age and prior cesarean section to controls (1:3) without accreta. The association between CET and accreta was modeled using conditional logistic regression, controlling a priori for age and placenta previa. Receiver operating characteristic curves were used to determine thresholds of endometrial thickness and peak serum E2 levels related to accreta.

Main outcome measure(s): Placenta accreta.

Result(s): Univariate predictors of accreta were non-Caucasian race (odds ratio [OR] 2.85, 95% confidence interval [CI] 1.25-6.47); uterine factor infertility (OR 5.80, 95% CI 2.49-13.50); prior abdominal or laparoscopic myomectomy (OR 7.24, 95% CI 1.92-27.28); and persistent or resolved placenta previa (OR 4.25, 95% CI 1.94-9.33). In multivariate analysis, we observed a significant association between CET and accreta (adjusted OR 3.20, 95% CI 1.14-9.02), which remained when analyses were restricted to cases of accreta with morbid complications (adjusted OR 3.87, 95% CI 1.08-13.81). Endometrial thickness and peak serum E2 level were each significantly lower in CET cycles and those with accreta.

Conclusion(s): Cryopreserved ET is a strong independent risk factor for accreta among patients using IVF and/or ICSI. A threshold endometrial thickness and a "safety window" of optimal peak E2 level are proposed for external validation.