Antibiotic Prophylaxis During Pregnancy Shows No Significant Benefit on Birth Weight: Trial Shows

The randomized, double-blind, placebo-controlled trial was led by Bernard Chasekwa and colleagues from the Zvitambo Institute for Maternal and Child Health Research in Harare. Researchers enrolled 993 pregnant women, including 131 with HIV infection, to examine whether daily administration of trimethoprim–sulfamethoxazole could lead to healthier birth weights by mitigating maternal infections, which are known contributors to low birth weight and other neonatal complications.

Participants were randomized to receive either the antibiotic (960 mg daily) or a placebo, beginning no earlier than 14 weeks into pregnancy and continuing until delivery. The median gestational age at which treatment began was 21.7 weeks. The primary endpoint of the study was infant birth weight.

Key Findings:

• The average birth weight in the antibiotic group was 3,040 grams.
• The average birth weight in the placebo group was 3,019 grams.
• The 20-gram difference between the two groups was not statistically significant.
• The antibiotic intervention did not show a measurable effect on birth weight.
• The frequency of adverse events was comparable in both groups.
• The antibiotic regimen was generally safe but did not demonstrate a clear benefit in improving birth weight outcomes.

Trimethoprim–sulfamethoxazole is often used to prevent bacterial infections in people with compromised immunity, including those with HIV. Its potential application in improving pregnancy outcomes has been of interest, particularly in low-resource settings where maternal infections are common and access to advanced medical care is limited.

However, the trial’s findings suggest that this specific prophylactic strategy may not yield the anticipated benefits for birth weight, a key indicator of neonatal health. Researchers emphasized the importance of continuing to explore other interventions to address poor birth outcomes, particularly in sub-Saharan Africa, where such risks remain high.

“Our results indicate that while trimethoprim–sulfamethoxazole is well-tolerated during pregnancy, it does not significantly affect birth weight,” the authors concluded. “Future studies should focus on identifying more effective approaches to reducing infection-related pregnancy complications.”

The trial adds to the growing body of evidence guiding maternal health policies, underscoring the need for evidence-based approaches tailored to the specific challenges faced in different global regions.

Reference:

Chasekwa, B., et al. (2025) A Trial of Trimethoprim–Sulfamethoxazole in Pregnancy to Improve Birth Outcomes. New England Journal of Medicine. doi.org/10.1056/NEJMoa2408114.