Infants ingest minimal amounts of antiretroviral medications through breast milk when mothers maintain viral suppression, according to a study published on October 20, 2026, in the JAIDS Journal of Acquired Immune Deficiency Syndromes.
The multicenter investigation conducted in the Netherlands examined whether maternal human immunodeficiency virus medications transfer to nursing infants. Researchers tracked mother-infant pairs where women living with the virus chose to breastfeed while maintaining antiretroviral therapy. The findings indicate that infant drug exposure remains well below established safety thresholds during lactation.
RID and Viral Suppression Ensure Infant Safety
- Relative Infant Dose (RID): This metric calculates the percentage of the maternal drug dose that reaches the nursing infant through milk, adjusted for infant body weight. All calculated RIDs fell safely below the 10% safety cutoff.
- Viral Suppression: Maternal viral loads remained undetectable throughout the observation period, meaning the ribonucleic acid (RNA) levels in breast milk were either undetectable or extremely low.
- Infant Safety: No participating infant showed measurable plasma viral load during or after the breastfeeding period, and growth trajectories remained normal.
Measuring Antiretroviral Transfer in Breast Milk
L.C. van der Wekken-Pas, of Radboud University Medical Center in Nijmegen, led the research team in evaluating prospective data from 16 mother-infant pairs alongside retrospective biobank data from five participants. The prospective cohort had a median maternal age of 35 years, while the retrospective cohort had a median maternal age of 31 years. Participants maintained their established antiretroviral regimens for at least two weeks before sampling began at routine monthly postpartum visits.
Investigators used mass spectrometry to measure drug concentrations in maternal plasma, pumped breast milk, and infant plasma. They calculated the breast milk-to-plasma ratio alongside the relative infant dose, assuming a standard breast milk intake of 150 milliliters per kilogram daily. For medications lacking specific pediatric approval, researchers applied an RID threshold of less than 10% as the benchmark for safety.
The highest calculated relative infant dose was 6.94% for efavirenz. For dolutegravir—which was utilized by 11 of the 16 prospective participants—the relative infant dose measured just 0.94%. Emtricitabine and tenofovir from tenofovir alafenamide fumarate both exhibited breast milk-to-plasma ratios exceeding 1, yet corresponding infant plasma levels remained minimal. The median level for emtricitabine stayed at 0.011 milligrams per liter, while tenofovir levels from tenofovir alafenamide fumarate were too low to quantify.
Maternal Viral Suppression Correlates with Healthy Infant Growth
Maternal plasma viral suppression held steady across all participants throughout the study timeline. Out of 36 tested breast milk samples, 33 showed zero detectable HIV RNA copies, while three measured below 40 copies per milliliter. Testing confirmed that no infant developed a measurable plasma viral load while breastfeeding or at four and eight weeks after nursing ceased.
Infant growth metrics showed no developmental anomalies related to drug exposure. None of the infants were born small for gestational age, and those weighed multiple times exhibited normal weight trajectories. Researchers noted that one newborn presented with trisomy 21 and congenital cardiac malformations requiring surgical intervention, but recorded no additional serious adverse events across the cohort.
Study limitations included a small overall sample size and restricted regimen diversity. Observations concentrated primarily on nucleoside reverse transcriptase inhibitors and dolutegravir. The pragmatic study design also meant that drug intake schedules and sampling times were not strictly standardized, requiring some data imputation.
Consult Specialists If Viral Suppression Is Unverified
Breastfeeding while managing HIV requires strict adherence to prescribed antiretroviral therapy and verified viral suppression. Patients experiencing treatment fatigue, irregular dosing schedules, or detectable viral loads must consult a specialist before initiating lactation.
Healthcare providers advise against breastfeeding if maternal viral suppression is unverified or if drug resistance is suspected. Immediate medical evaluation is required if an infant exhibits unusual lethargy, feeding difficulties, or unexpected gastrointestinal symptoms while exposed to breast milk containing antiretroviral agents.
The addition of these data to previous studies should reassure both women living with HIV and their healthcare professionals in pursuing breastfeeding in case a woman with good drug adherence and a suppressed plasma viral load prefers to do so.
The study received funding support from ZonMW. Individual authors reported disclosing financial relationships, including research grants, speaker fees, travel reimbursements, and advisory board participation involving ViiV Healthcare, Gilead Sciences, and Merck, alongside research grants from the Dutch Society of HIV physicians.
References
- JAIDS Journal of Acquired Immune Deficiency Syndromes: Multicenter evaluation of antiretroviral drug exposure in breastfed infants, October 2026.
- Radboud University Medical Center: Clinical pharmacokinetic and virological assessments in postpartum women living with HIV.
