In vitro fertilization as an independent risk factor for placenta accreta spectrum

BACKGROUND: Placenta accreta spectrum is well known for its association with catastrophic maternal outcomes. However, its pathophysiology is not well defined. There have been emerging data that in vitro fertilization may be a risk factor for placenta accreta spectrum. OBJECTIVE: We investigated the hypothesis that in vitro fertilization is an independent risk factor for placenta accreta spectrum. STUDY DESIGN: A retrospective analysis of all deliveries in a prospective, population-based cohort (2012-2019) was performed in a tertiary academic center. Primary outcome variable was placenta accreta spectrum. Univariate analysis was performed on potential risk factors for predicting placenta accreta spectrum, and a multivariate model was designed to best fit the prediction of placenta accreta spectrum adjusted for risk factors such as cesarean delivery, placenta previa, age, and parity. History of previous cesarean delivery was known as a risk factor for both placenta previa and placenta accreta spectrum; hence, the interaction between "placenta previa" and "previous cesarean delivery" was included in the final model. Odds ratios were calculated as exponential of beta coefficients from the multivariate regression analysis. RESULTS: A total of 37,461 deliveries were included in this analysis, 5464 (15%) of which had a history of cesarean delivery, 281 (0.7%) had placenta previa in their index pregnancy, and 571 (1.5%) had in vitro fertilization pregnancy. The frequency of placenta accreta spectrum was 230 (0.6%). Independent risk factors for placenta accreta spectrum were in vitro fertilization pregnancy (adjusted odds ratio, 8.7; 95% confidence interval, 3.8-20.3), history of previous cesarean delivery (adjusted odds ratio, 21.1; 95% confidence interval, 11.4-39.2), and presence of placenta previa (adjusted odds ratio, 94.6; 95% confidence interval, 29.3-305.1). After adjustment for number of previous cesarean deliveries, the correlation persisted for in vitro fertilization (adjusted odds ratio, 6.7; 95% confidence interval, 2.9-15.6). CONCLUSION: Our data suggested that in vitro fertilization is an independent risk factor for placenta accreta spectrum, although its relative clinical importance compared with that of the presence of placenta previa and history of cesarean delivery is small. The pathophysiology behind this relationship remains to be investigated.