Aspirin use during pregnancy and placental pathology in obese women in a large prospective cohort study

Background: The placenta plays a critical role in the development of preeclampsia. Low-dose aspirin can prevent preeclampsia in high-risk women, but the mechanisms are unclear. We examined the association between aspirin use during pregnancy and the placental pathology in obese women to better understand how aspirin may work. Methods: Data were taken from the U.S. Collaborative Perinatal Project (CPP), a large prospective cohort study conducted at 12 centers from 1959 to 1976. Live singleton pregnancies (n=42,308) with information on placental pathology and aspirin exposure during pregnancy were included. Pre-pregnancy BMI >= 30.0 kg/m2 and 25.0 kg/m2 <= BMI < 30.0 kg/m2 were defined as obese (n=2,286) and overweight (n=5,673), respectively. Placental pathology examinations were performed by a team of trained pathologists according to a standard protocol. We further divided the placental pathology into three clusters: hypoxia-related, inflammation-related, and hemorrhage-related placental indicators. Generalized estimating equation was used to examine the association between aspirin use during pregnancy and placental pathological changes adjusting for potential confounders.Results: Among obese women, aspirin use in one, two and three trimesters during pregnancy tended to have lower risks of hypoxia-related placental pathologic changes (OR=0.99, 95% CI: 0.70-1.39; OR=0.77, 95% CI: 0.48-1.24; OR=0.43, 95% CI: 0.20-0.91, respectively) and hemorrhage-related placental pathologic changes (OR=0.89, 95% CI: 0.60-1.32; OR=0.50, 95% CI: 0.28-0.89; OR=0.49, 95%CI: 0.21-1.19, respectively) compared to women who did not use aspirin during pregnancy. In addition, aspirin use in all three trimesters may have a protective effect on inflammation-related placental pathologic changes (OR=0.43, 95% CI: 0.15-1.25). The positive association was not as prominent in overweight women. Aspirin use was associated with lower risks of thrombus, calcification, cysts, fibrin deposition, syncytium-nuclear clumping, necrosis, macrophage, and neutrophilic infiltration in the placentae.Conclusions: Our study suggests that aspirin use during pregnancy was associated with a decreased risk of placental pathological changes in obese women. The positive association increase with the duration of use.