Meher, S., Duley, L., Hunter, K., & Askie, L. (2017). Antiplatelet therapy before or after 16 weeks’ gestation for preventing preeclampsia: an individual participant data meta-analysis. American Journal of Obstetrics and Gynecology, 216(2), 121–128.e2.

This study was done to assess the optimum time for starting antiplatelet therapy for prevention of preeclampsia. Data suggest that administration of aspirin prior to 16 weeks gestation is optimal but the evidence is limited. This study was a subgroup analysis of a 32,217 patient meta-analysis comparing antiplatelet administration before and after 16 weeks gestation. The study assessed four outcomes, including preeclampsia, death of baby, preterm birth before 34 weeks, and small for gestational age baby.

No significant difference in effects of antiplatelet therapy where found for the two groups regarding the four outcomes assessed. The study was not able to assess whether there is a gestational age beyond which starting aspirin therapy may not be beneficial. Regardless, the results of this study show that aspirin should be started regardless of when a patient first presents for obstetrical care as the effect in reducing preeclampsia and other complications is comparable independent of start date.