The effect of 150 and 80 mg doses of aspirin on preventing preterm birth in high-risk pregnant women.

Objectives: Preterm birth (PTB) is the common cause of neonatal mortality nationwide. The present study aimed to evaluate the efficacy of different doses of aspirin in preventing PTB in high-risk pregnant women. As secondary outcomes, other perinatal complications were compared.

Methods: This double-blind randomized clinical trial was conducted on high-risk pregnant women with impaired placental perfusion diagnosed in the first trimester of pregnancy referring to the perinatal centers affiliated to Shiraz university of Medical Sciences between February 2020 and March 2021. The subjects were randomly divided in two groups administered with 150 or 80 mg aspirin every night from 11 to 13+6 weeks until 36 weeks or delivery. This study is registered in the Iranian Registry of Clinical Trials (IRCT20140317017035N6; http://www.irct.ir/). Univariate and multiple logistic regressions were applied using SPSS 22.

Results: A total of 101 subjects received 80 mg aspirin and 89 ones received 150 mg aspirin. The results of multiple analysis revealed a significantly lower odds of PTB (OR 0.4 0.19, 0.99)) in the 150 mg group compared to the 80 mg group. As secondary outcomes, preeclampsia (PEC) and PEC with severe features (PECsf) were lower (OR 0.2 (0.06, 0.82) and 0.1 (0.01, 0.92), respectively); however, fetal age and neonatal weight were higher in the 150 mg group (OR 1.2 (1.04, 1.33) and 1.001 (1-1.001), respectively).

Conclusions: The study findings indicated that, compared with 80 mg of aspirin, taking 150 mg of aspirin reduced PTB and perinatal complications in high risk pregnant women.