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Daily aspirin may reduce preterm birth risk among first-time mothers

Women who took low-dose aspirin were 11% less likely to give birth before the 37th week of pregnancy

Ingrid Torjesen

Friday, 24 January 2020

Daily low-dose aspirin during pregnancy may lower the risk for preterm birth among first-time mothers, suggests a study* published in The Lancet.

The study, which was funded by the US National Institutes of Health, found that women were 11.6% less likely to deliver before the 37th week of pregnancy if they took daily low-dose aspirin, compared to those given a placebo.

The study involved 11,976 women with a first-time pregnancy enrolled at seven sites in India, Pakistan, Zambia, Democratic Republic of the Congo, Guatemala and Kenya. Roughly half were assigned at random to receive 81mg of aspirin daily and the other group received a daily placebo. Women were included in the study only if they maintained a pregnancy for more than 20 weeks.

Preterm birth (before 37 weeks) occurred in 11.6% of the women who took aspirin and in 13.1% of the women who took the placebo. Similarly, birth before 34 weeks (early preterm delivery) occurred in 3.3% of the aspirin group and 4% of the placebo group (a 25% reduction). Women in the aspirin group also had a lower rate of perinatal mortality (stillbirth or newborn death in the first seven days of life), compared to the placebo group (45.7 per 1,000 births vs 53.6 per 1,000 births). The risk of high blood pressure disorders of pregnancy at term did not differ significantly between the groups.

The authors note that the low cost and safety of low-dose aspirin therapy suggest that it could be easily adapted for widescale use.

"Our results suggest that low-dose aspirin therapy in early pregnancy could provide an inexpensive way to lower the preterm birth rate in first-time mothers," said Marion Koso-Thomas, of the US National Institute of Child Health and Human Development Pregnancy and Perinatology Branch.

Preterm birth is the most common cause of infant death and the leading cause of long-term neurological disability in children, and while advances in newborn care have already improved survival for preterm infants in many high-income countries, this care is limited or unavailable in less well-resourced settings.  Earlier studies have suggested that low-dose aspirin may reduce the risk of preterm birth and preeclampsia, but were not large enough to statistically determine the therapy's effectiveness in reducing preterm birth.


*Hoffman MK, Goudar SS, Kodkany BS, et al. Low-dose aspirin for the prevention of preterm delivery in nulliparous women with a singleton pregnancy (ASPIRIN): a randomised, double-blind, placebo-controlled trial. The Lancet. Published: 25 January 2020, DOI: 10.1016/S0140-6736(19)32973-3

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