Trial Shows Low Cost Antibiotic Use May Reduce Preterm Births in Women with HIV

A new study published in the New England Journal of Medicine has found that a commonly used, low-cost antibiotic may significantly reduce the risk of preterm births, particularly among pregnant women living with HIV. The findings come from the Cotrimoxazole for Mothers to Improve Birthweight in Infants (COMBI) trial, a randomized controlled study.

Globally, one in four live-born infants is either preterm, small for gestational age, or has a low birth weight—conditions that contribute heavily to under-5 child mortality. Prematurity is now the leading cause of death among children under five. Maternal infections and inflammation, especially in women with HIV, have been closely linked to adverse birth outcomes. The COMBI trial was designed to investigate whether administering a daily dose of trimethoprim–sulfamethoxazole—a broad-spectrum antimicrobial with anti-inflammatory properties—could reduce these risks.

A total of 993 pregnant women from three antenatal clinics in Shurugwi, Zimbabwe, participated in the study. They were randomly assigned to receive either 960 mg of the antibiotic or a placebo daily. All participants received routine antenatal care, and detailed data on their birth outcomes were collected and analyzed.

While the study found no significant difference in birthweights between the two groups, it revealed a notable reduction in preterm births. Only 6.9% of women in the antibiotic group delivered prematurely, compared to 11.5% in the placebo group. Strikingly, among the 131 women with HIV, just 2% of births in the antibiotic group were preterm, compared with 14% in the placebo group. Babies in the treatment group also had an average increase of 177 grams in birthweight.

Bernard Chasekwa, first author, said: “Our trial, conducted within routine antenatal care and enrolling women predominantly from rural areas, showed that trimethoprim-sulfamethoxazole did not improve birthweight, which was our main outcome. However, there was an intriguing suggestion that it may have improved the length of pregnancy and reduced the proportion of preterm births. We now need to repeat this trial in different settings around the world to see whether antibiotics during pregnancy can help reduce the risk of prematurity.”

Reference: https://www.qmul.ac.uk/media/news/2025/medicine-and-dentistry/fmd/antibiotics-taken-during-pregnancy-may-reduce-preterm-births.html