Low dose aspirin prevents preterm birth in nulliparous women: AJOG

The administration of low dose aspirin in healthy nulliparous women is associated with a substantial decrease in spontaneous preterm birth (PTB) <34weeks without co-morbidities, according to a new study published in the American Journal of Obstetrics and Gynecology.

Maria Andrikopoulou, Department of Obstetrics and Gynecology, NYU Winthrop University Hospital, Mineola, NY, and colleagues conducted the study to determine whether low dose aspirin reduces the rate of spontaneous PTB in nulliparous women without medical co-morbidities.

Preterm birth is one of the leading causes of perinatal mortality and morbidity. Clinical data suggests that low dose aspirin may decrease the rate of overall PTB, but investigators have speculated that this is likely due to a decrease in medically indicated PTB through its effect on the incidence of preeclampsia and other placental diseases. The researchers hypothesized that low dose aspirin may also impact the mechanism of spontaneous preterm labor.

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This is a secondary analysis of a randomized, placebo-controlled trial of low dose aspirin for 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, non-anomalous gestations. Women were eligible if they had prior pregnancy terminations, but not prior spontaneous pregnancy loss <20 weeks(wks). Current pregnancies that resulted in a loss or termination <20wks, antepartum stillbirth or had missing follow-up data were excluded. The treatment intervention was 60mg of aspirin, initiated at 13-25wks gestation or matching placebo. The primary outcome was spontaneous PTB <34wks gestation. Secondary outcomes included spontaneous PTB <37 and overall PTB <37 and <34wks. Baseline demographics, primary, and secondary outcomes were compared between treatment groups. A logistic regression model was used to adjust for confounders related to spontaneous PTB.

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.

Key Findings:

• The rate of spontaneous PTB <34wks was 1.03% (n=13) and 2.34% (n=30) in the low dose aspirin and placebo group, respectively (OR 0.43, 95% CI 0.26-0.84).


• The rate of spontaneous PTB < 37wks was 6.58% (n=83) in low dose aspirin and 7.03% (n=90) in placebo group (OR 0.97, 95% CI 0.71-1.33) and the rate of overall PTB<37 weeks was 7.84% (n=99) in low dose aspirin and 8.2% (n=105) in placebo group (OR 0.97, 95% CI 0.72-1.31).


• After adjustment for variables that were clinically relevant or statistically significant, including BMI, race, tobacco use, marital status and education level, there was a significant reduction in spontaneous PTB <34wks in the low dose aspirin group (aOR 0.46, 95% CI 0.23-0.89).


• The rates of overall PTB <34 and <37wks and spontaneous PTB <37wks were similar in women that received low dose aspirin compared to placebo.

"Low dose aspirin is associated with a substantial decrease in spontaneous PTB <34wks in healthy nulliparous women without co-morbidities. These findings suggest a new therapeutic option for PTB prevention that requires further study," concluded the authors.

For further information log on to https://doi.org/10.1016/j.ajog.2018.06.011