Impact of the ACOG guideline regarding low dose aspirin for prevention of superimposed preeclampsia in women with chronic hypertension

BACKGROUND: Patients with chronic hypertension are at increased risk for superimposed preeclampsia. The 2016 American College of Obstetricians and Gynecologists (ACOG) guideline recommended initiating 81 mg daily aspirin for all pregnant women with chronic hypertension to prevent superimposed preeclampsia. OBJECTIVE: 1) To evaluate the rates of implementation of the 2016 ACOG guideline over time; 2) To evaluate the effectiveness of aspirin for the prevention of superimposed preeclampsia and other adverse maternal and neonatal outcomes in women with chronic hypertension before and after this guideline. STUDY DESIGN: This is a retrospective study of women with chronic hypertension who delivered at Thomas Jefferson University Hospital from 1/2014 through 6/2018. This cohort of women with chronic hypertension was divided into 2 groups, before and after the ACOG recommendation published in 7/2016. Daily 81 mg aspirin was initiated between 12 to 16 weeks. We excluded multiple gestations and incomplete records. The primary outcome was incidence of superimposed preeclampsia, and secondary outcomes were incidence of superimposed preeclampsia with or without severe features, small for gestational age, and preterm birth \u3c37 weeks. Subgroup analysis based on risk stratification was evaluated in women with chronic hypertension requiring antihypertensive medication, history of preeclampsia and pre-gestational diabetes. RESULTS: We identified 457 pregnant women with chronic hypertension, 203 in the post-ACOG group and 254 in the pre-ACOG group. Aspirin 81 mg was offered to 142 (70%) in the post-ACOG group and 18 (7.0%) in the pre-ACOG group. Maternal demographics were not significantly different. The overall incidence of superimposed preeclampsia was not significantly different: 87 (34.3%) vs. 72 (35.5%), p=0.79 in the pre and post ACOG guideline groups, respectively. Superimposed preeclampsia with severe features significantly increased: 32 (12.6%) vs 9 (4.4%), p\u3c0.01 while superimposed preeclampsia without severe features significantly decreased: 55 (21.7%) vs 63 (31.0%) p=0.03. There were no significant differences in small for gestational age neonates or preterm birth \u3c37 weeks incidences between groups. There were no significant differences in the subgroup analysis based on the severity of chronic hypertension requiring antihypertensive medication, history of preeclampsia, or pregestational diabetes. CONCLUSION: After the adoption of the ACOG guidelines in 70% of the cohort, superimposed preeclampsia, small for gestational age, and preterm birth were not significantly decreased after implementation of aspirin 81mg initiated between 12 to 16 weeks of gestation