February 11, 2020

Low-dose aspirin reduces preterm birth among first-time mothers

At a Glance

  • In a large trial, daily low-dose aspirin reduced the risk of preterm birth (before 37 weeks) by 11% and early preterm birth (before 34 weeks) by 25% among first-time mothers.
  • The low cost and safety of aspirin therapy suggest it could be used in diverse settings around the world to reduce preterm birth.
Young mother kissing her newborn on the forehead The study tested whether low-dose aspirin could help prevent preterm birth.FatCamera / iStock / Getty Images Plus

A baby born before 37 weeks of pregnancy is considered preterm. Preterm birth is the most common cause of infant death and a leading cause of long-term disability in children. Women in low- and middle-income countries are at greater risk of giving birth prematurely. While much research has focused on preventing preterm birth, scientists are still looking for effective therapies that don’t require large resources.

Past studies suggested that daily low-dose aspirin might prevent preterm birth and preeclampsia—a potentially life-threatening blood pressure disorder during pregnancy or soon after giving birth. But these studies weren’t large enough to prove aspirin’s effectiveness.

Researchers designed a large, multi-country trial to test whether taking daily low-dose aspirin, starting early in pregnancy, would reduce preterm birth among first-time mothers. The study, led by Dr. Matthew K. Hoffman of ChristianaCare, was funded by NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). Findings appeared in the Lancet on January 25, 2020

The team enrolled about 12,000 women at sites in India, Pakistan, Zambia, Democratic Republic of the Congo, Guatemala, and Kenya. The first-time mothers ranged from ages 14 to 40. They were randomly assigned to take low-dose aspirin (81 mg) each day or a similar-looking placebo. The participants, research staff, and health care providers were unaware of which participants were taking aspirin or placebo.

Treatment began during the first trimester, as early as the sixth week of pregnancy, and continued until the end of the 36th week of pregnancy or until giving birth. Deliveries at 20 weeks or later were included in the results.

The team found that woman taking daily low-dose aspirin were 11% less likely to deliver prematurely (before 37 weeks). Preterm birth occurred in 11.6% of the women taking aspirin compared to 13.1% of the women taking placebo.

Taking low-dose aspirin also reduced the risk of early preterm delivery (giving birth before 34 weeks) by 25%. Early preterm delivery occurred in 3.3% of the aspirin group and 4% of the placebo group. Aspirin therapy reduced perinatal mortality—stillbirth or newborn death in the first week of life—as well (45.7 per 1,000 births with aspirin vs 53.6 per 1,000 births with placebo). The researchers found no difference in the rates of preeclampsia or other blood pressure disorders between the two groups.

“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,” says study author Dr. Marion Koso-Thomas of NICHD.

Aspirin therapy could be useful for diverse groups of pregnant women in various clinical settings. Its low cost and proven safety suggest it could be readily adopted worldwide, particularly in countries where medical resources are scarce.

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References: Low-dose aspirin for the prevention of preterm delivery in nulliparous women with a singleton pregnancy (ASPIRIN): a randomised, double-blind, placebo-controlled trial. Hoffman MK, Goudar SS, Kodkany BS, Metgud M, Somannavar M, Okitawutshu J, Lokangaka A, Tshefu A, Bose CL, Mwapule A, Mwenechanya M, Chomba E, Carlo WA, Chicuy J, Figueroa L, Garces A, Krebs NF, Jessani S, Zehra F, Saleem S, Goldenberg RL, Kurhe K, Das P, Patel A, Hibberd PL, Achieng E, Nyongesa P, Esamai F, Liechty EA, Goco N, Hemingway-Foday J, Moore J, Nolen TL, McClure EM, Koso-Thomas M, Miodovnik M, Silver R, Derman RJ; ASPIRIN Study Group. Lancet. 2020 Jan 25;395(10220):285-293. doi: 10.1016/S0140-6736(19)32973-3. PMID: 31982074.

Funding: NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).