OBJECTIVE: This is a secondary analysis of a randomized, placebo-controlled trial of low-dose
aspirin for the prevention of
preeclampsia in healthy, low-risk, nulliparous women. Low-risk women were defined by the absence of
hypertension, renal disease, diabetes, other endocrine disorders,
seizures,
heart disease, or
collagen vascular disease. Our study was limited to singleton, nonanomalous gestations. Women were eligible if they had prior pregnancy terminations but not prior spontaneous pregnancy loss <20 weeks. Current pregnancies that resulted in a loss or termination <20 weeks or antepartum
stillbirth or had missing follow-up data were excluded. The treatment intervention was 60 mg of
aspirin, initiated at 13-25 weeks' gestation or matching placebo. The primary outcome was spontaneous
preterm birth <34 weeks' gestation. Secondary outcomes included spontaneous
preterm birth <37 weeks and overall
preterm birth <37 and <34 weeks. Baseline demographics and primary and secondary outcomes were compared between treatment groups. A logistic regression model was used to adjust for confounders related to spontaneous
preterm birth.
RESULTS: Of 2543 included women, 1262 (49.6%) received low-dose
aspirin and 1281 (50.4%) placebo. Baseline characteristics were similar between groups, except for marital status. The rate of spontaneous
preterm birth <34 weeks was 1.03% (n = 13) and 2.34% (n = 30) in the low-dose
aspirin and placebo group, respectively (odds ratio, 0.43, 95% confidence interval, 0.26-0.84). Additionally, the rate of spontaneous
preterm birth <37 weeks was 6.58% (n = 83) in the low-dose
aspirin group and 7.03% (n = 90) in the placebo group (odds ratio, 0.97, 95% confidence interval, 0.71-1.33), and the rate of overall
preterm birth <37 weeks was 7.84% (n = 99) in the low-dose
aspirin group and 8.2% (n = 105) in the placebo group (odds ratio, 0.97, 95% confidence interval, 0.72-1.31). After adjustment for variables that were clinically relevant or statistically significant, including body mass index, race, tobacco use, marital status, and education level, there was a significant reduction in spontaneous
preterm birth <34 weeks in the low-dose
aspirin group (adjusted odds ratio, 0.46, 95% confidence interval, 0.23-0.89). The rates of overall
preterm birth <34 and <37 weeks and spontaneous
preterm birth <37 weeks were similar in women who received low-dose
aspirin compared with placebo.
CONCLUSION: