Trimethoprim-Sulfamethoxazole Prophylaxis Shows No Benefit for Infant Birth Weight in HIV-Positive Pregnancies

A recent randomized trial published in *The New England Journal of Medicine* has concluded that antenatal prophylaxis with trimethoprim-sulfamethoxazole does not result in a significant increase in birth weight or improvements in key birth outcomes for infants born to HIV-positive mothers. The study involved 993 women from Zimbabwe who were randomized to receive either the antibiotic regimen or a placebo during their pregnancies. This research is particularly relevant as it addresses the prevalence of preterm birth and low birth weight, which affect one in four newborns globally and are exacerbated by maternal infections, particularly in the context of HIV.

The trial aimed to assess whether the use of trimethoprim-sulfamethoxazole, a broad-spectrum antimicrobial, could improve birth outcomes. Patients were enrolled from three antenatal clinics in Shurugwi, Zimbabwe, with inclusion criteria that ensured they were not already receiving the medication, had no contraindications, and had a confirmed positive urine pregnancy test. The data collection included demographic and clinical information, with trained midwives conducting ultrasonographies to measure gestational duration.

Participants were randomly assigned in a 1:1 ratio to receive either the trimethoprim-sulfamethoxazole regimen—comprising two 480-mg tablets daily—or a placebo, indistinguishable in appearance. Follow-up appointments were scheduled throughout the pregnancy to monitor adherence, side effects, and obstetrical complications.

As reported in the study, the final analysis showed no significant difference in average birth weight between the two groups: 3040±460 grams for the trimethoprim-sulfamethoxazole group compared to 3019±526 grams for the placebo group, yielding a mean difference of just 20 grams, which was not statistically significant. Secondary outcomes, such as rates of low birth weight and small for gestational age, also showed no meaningful differences.

Despite the initial hypothesis that antibiotics could enhance birth outcomes during pregnancy, the results of this trial illustrate the complexity of maternal health in the context of HIV. "In this trial, we found that a universal, pragmatic strategy of antenatal trimethoprim-sulfamethoxazole in a district in Zimbabwe with a high prevalence of HIV did not lead to a significant improvement in birth weight," concluded the study authors, including Dr. Blessing Chasekwa from the University of Zimbabwe and co-authors from various institutions.

The implications of these findings are substantial for public health strategies targeting maternal and infant health, especially in regions with high rates of HIV. While the use of prophylactic antibiotics has been posited as a method to mitigate risks associated with maternal infections, this study suggests that such strategies may not yield the anticipated benefits in terms of birth weight. Future research may focus on alternative interventions or combined strategies that address the multifaceted challenges faced by HIV-positive pregnant women.

In light of these findings, healthcare providers and policymakers may need to reassess existing guidelines regarding antibiotic prophylaxis during pregnancy, particularly in HIV-affected populations. The trial's results contribute to the ongoing discourse on optimizing maternal health outcomes and underline the critical need for holistic approaches that consider the broader determinants of health in vulnerable populations.