Low-Dose Aspirin Might Help Prevent Preterm Births

A daily baby aspirin helped first-time mothers lower their chances of delivering too soon in a new clinical trial, though it's not clear the practice should become routine everywhere.

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The trial, which was run in six lower-income countries, found that giving first-time mothers a daily low-dose aspirin reduced their risk of preterm birth by 11%. Their chances of a very early delivery -- before the 34th week of pregnancy -- were cut by one-quarter.

"This is a very important finding," said Dr. Rahul Gupta, chief medical and health officer for the nonprofit March of Dimes.

Low-dose aspirin is readily available, cheap and safe, noted Gupta, who was not involved in the trial. That means it could have a real impact in low-income countries, where infant deaths from preterm birth are particularly common.

But whether the findings would extend to the United States and other high-income countries is not yet known, Gupta added.

He said it could be worthwhile to conduct a similar trial in the United States -- with special attention to enrolling groups with higher rates of preterm delivery, such as black women.

In 2018, the rate of preterm birth was 14% among black women, versus 9% among white women, according to the U.S. Centers for Disease Control and Prevention. That's about a 50% difference.

In the United States, low-dose aspirin -- 81 milligrams per day -- is already recommended for pregnant women at high risk of preeclampsia, a condition marked by dangerously high blood pressure and protein in the urine. One of its potential consequences is preterm birth, and studies on aspirin and preeclampsia had suggested the drug might help prevent those early deliveries.

That led to the latest trial, which recruited nearly 12,000 women in the Democratic Republic of the Congo, Guatemala, India, Kenya, Pakistan and Zambia. All were first-time mothers-to-be; half were randomly assigned to take a daily low-dose aspirin, while half received placebo pills.

The women started on aspirin or placebo as early as the sixth week of pregnancy and continued through the 36th week or until delivery.

In the end, women using aspirin were less likely to give birth prematurely (before the 37th week of pregnancy): 11.6% did, versus 13.1% of women in the placebo group. Their rate of early preterm birth (before week 34) was cut, too -- with 3.3% delivering that early, versus 4% of placebo users.

The findings are strong enough to support routine use of low-dose aspirin in low- to mid-income countries, said study co-author Dr. Marion Koso-Thomas.

Like Gupta, she pointed to the pros of aspirin's low cost and simplicity. It's also safe, said Koso-Thomas, who is with the Pregnancy and Perinatology Branch at the U.S. National Institute of Child Health and Human Development.

Her team found no increased risks of problems, such as bleeding, for moms or babies.

And when preterm births are prevented, Koso-Thomas said, the consequences of it -- including infant deaths -- can be, too.

In the trial, perinatal deaths -- which include stillbirths and newborn deaths within the first week of life -- were reduced in the aspirin group. Among women who took aspirin, there were just under 46 perinatal deaths per 1,000 pregnancies, compared with just under 54 per 1,000 in the placebo group.

The findings were published in the Jan. 25 issue of The Lancet.

Whether the findings can be translated to the United States or other high-income countries is not clear, however.

Since preterm births are more common in low-income countries, it's not clear that the same "statistically meaningful universal benefit" would be seen elsewhere, said Dr. Julie Quinlivan, of the University of Notre Dame Australia.

She wrote an editorial published with the study.

Pregnant women should always talk to their doctor before using any medication, including low-dose aspirin, Quinlivan said.

And when it comes to lowering the risk of preterm birth, there are some other proven measures, she said: quitting smoking; getting the flu vaccine; treating anemia or any genital or urinary infections before pregnancy; eating a diet rich in omega-3 fatty acids, or considering a fish oil supplement.

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