Exposed, But Not Infected: What Happens to Babies Born to Mothers Living With HIV

Three studies published in 2026 followed these children from the day they were born to their third birthday — here is what they found, and what it means for families

Almost every baby born today to a mother living with HIV does not get the virus, which is one of the real triumphs of modern pregnancy care. Even so, doctors have wondered for years whether being exposed to HIV and to HIV medicines before birth leaves any lasting mark. Three studies published in 2026 followed these children from birth to age three, and their answer is more reassuring — and more useful — than the worry suggests.

What it means to be "exposed" but not infected

When a woman living with HIV takes antiretroviral medicines through her pregnancy, the virus in her blood usually becomes undetectable, and the chance of passing it to her baby drops to around two in a hundred or lower. Her baby is tested after birth, the test comes back negative, and the family is told the news everyone was hoping for.

Doctors have a term for these children: HIV-exposed and uninfected. There are more than sixteen million of them worldwide, and over nine in ten live in sub-Saharan Africa, where HIV is most common. They were surrounded by HIV and by HIV medicines while they were growing in the womb, but they do not have the virus and never will from that exposure.

The worry that families inherited from an earlier era

The question that has hung over these children for decades is whether that exposure matters anyway. It is not an idle worry. In the years before HIV treatment in pregnancy was widely available, researchers who combined the results of many studies found that exposed children died somewhat more often in early childhood than children whose mothers did not have HIV [1], and were admitted to hospital more often, and stayed longer, with ordinary childhood infections such as chest infections and diarrhoea [2], [3].

That evidence came from a very different world. In those years, many mothers started treatment late in pregnancy, or not at all; many had advanced illness; and many were advised not to breastfeed for fear of passing on the virus, losing all the protection that breast milk gives. It has never been clear how much of the difference was caused by the HIV exposure itself and how much by the hard circumstances that so often travelled with it — illness in the family, interrupted breastfeeding, and poverty. Researchers who set out the possible explanations listed them side by side: the mother's own immune system being on alert during pregnancy, the medicines crossing the placenta, fewer protective antibodies being passed on, shorter breastfeeding, and the social conditions around the family [4].

The picture began to change as treatment became routine. A large study in South Africa, where almost all mothers were on treatment, found much less difference than earlier work had suggested [5]. A study in Belgium found that when mothers began treatment before they became pregnant, rather than during the pregnancy, the difference in hospital admissions largely disappeared [6]. And in Botswana, where more than 98 out of every 100 pregnant women with HIV are on treatment, researchers following 462 babies through their first year found no difference at all in how often exposed and unexposed babies were admitted to hospital with an infection or died — about 9 in every 100 exposed babies compared with about 7 in every 100 unexposed babies, a gap small enough to be chance [7].

What the three new studies did

The three 2026 studies pick up the question at three different ages.

The first was done at three hospitals in Yaoundé, the capital of Cameroon [8]. Researchers collected blood from the umbilical cord of 140 newborns at the moment of birth — 65 born to mothers with HIV and 75 born to mothers without — and examined the cells and the chemical messengers in it. They were strict about who could take part: every mother with HIV had to have no detectable virus in her blood, and mothers in both groups with other infections or long-term illnesses were left out, so that anything they found could be attributed to the HIV exposure itself rather than to something else.

The second was also done in Yaoundé, at a different hospital, and followed babies rather than sampling them once [9]. Researchers enrolled 210 pregnant women — about half living with HIV — and then saw their babies six times during the first year, weighing and measuring them, asking mothers what symptoms the baby had had, testing swabs for seven common infections, and measuring antibodies in the blood.

The third was the largest and longest [10]. It followed 1,227 mothers and children in eight regions of three Chinese provinces — Yunnan, Guangxi and Xinjiang — from birth to the third birthday. For every exposed child, two comparison children of the same sex, the same ethnic background and a similar length of pregnancy were followed alongside.

What the newborn blood tests showed

At the moment of birth, there were differences [8]. The exposed babies' cord blood had fewer white blood cells overall, fewer of the cells called neutrophils that deal with bacteria, and slightly less haemoglobin, the substance that carries oxygen. Their blood also carried a chemical signature of inflammation: more of two messenger proteins that switch inflammation on, and less of one that calms it down.

These differences are real, but they are also small and mostly invisible. The exposed and unexposed babies weighed the same at birth — an average of about 3,281 grams compared with 3,289 grams, a difference of eight grams. Head size was very slightly smaller in the exposed group, but not by enough to be certain it was not chance. The study looked at babies only once, on the day they were born, so it cannot tell us whether these differences lasted a week, a year, or not at all.

What the first year of life looked like

The second study is the one that most directly answers a parent's question, and its overall answer is reassuring [9]. Over twelve months, exposed and unexposed babies grew similarly, caught the same infections at about the same rate, and had antibody levels that rose and fell along the same curves.

Two infections were common in both groups — cytomegalovirus, a virus most children meet early and shrug off, and rhinovirus, the ordinary common cold — while rotavirus, malaria, influenza and the chest virus RSV were almost absent in both. At six months, cytomegalovirus was actually more common in the unexposed babies.

Some differences did show up, but they came and went, and they mostly affected boys. Exposed boys were a little lighter at three months, and more exposed children were short for their age at certain visits. But when the researchers accounted for the family's financial circumstances, how the baby was fed, and the mother's age and length of pregnancy, those differences no longer stood out. Feeding is probably the biggest part of the explanation: about 31 in every 100 exposed babies were given formula, compared with 2 in every 100 unexposed babies.

What had changed by the third birthday

The Chinese study found the most consistent difference and, at the same time, the most practical explanation [10]. Exposed babies were born lighter — about 2,926 grams on average compared with 3,182 grams — and were more likely to be born early or small. They stayed slightly lighter and shorter than the comparison children at most check-ups through to age three, though the gap narrowed around 18 months and two years.

What made the difference was the interesting part. When the researchers asked which factors actually predicted poor growth, HIV exposure was not at the top of the list. Being born small was, raising the odds of poor nutrition by about 38 per cent. So was a mother having previously lost a baby. So was low household income — families with higher incomes had measurably better-grown children. How long the mother had been on HIV treatment made no difference at all. In other words, by age three, most of what separated these children from their peers was the same thing that separates any child from their peers: birth weight and household circumstances.

What this means for your baby

If your child was exposed to HIV before birth and tested negative, your child does not have HIV. The differences researchers can measure are small, most of them fade, and the ones that persist are driven by things other than the exposure — most of all by birth weight and by the resources a family has.

The most useful things are also the most ordinary. Keep the growth check-ups, because a growth chart plotted regularly will pick up a problem far earlier than any specialist test. Keep immunisations on schedule. And ask your team about breastfeeding: if you are on treatment with an undetectable viral load, breastfeeding is recommended, and the evidence that it protects exposed babies is strong. In Botswana, each extra month of exclusive breastfeeding cut the odds of a baby being hospitalised with an infection or dying by about 16 per cent [7], and studies in Nigeria, South Africa and Kenya have found the same protective effect [11], [12]. Many mothers were advised years ago not to breastfeed because of transmission fears [13]; for a mother whose virus is suppressed, that advice has changed.

It is also worth knowing that exposed children who do become unwell can be a little sicker once admitted, even though they fall ill no more often [14]. That is a reason to seek review sooner if your child seems genuinely unwell, not a reason to worry about every cold.

What researchers are working on next

Two large gaps remain. None of these three studies looked at how children learn, speak and develop, which is the area where the evidence is thinnest and which researchers have identified as the priority for the next generation of studies [15]. And all three describe an older set of HIV medicines; most programmes have since moved to a newer drug called dolutegravir, so the exposure being studied is already being replaced by a different one [16]. Studies now under way are following larger groups of children for longer, measuring development as well as growth, and looking separately at boys and girls — because these three studies disagreed about which sex fares worse, which usually means the difference is small and depends on where you look [17].

For now, the fair summary is a hopeful one. A generation of children who would once have been born with HIV are instead being born without it, growing up, and looking, by and large, like everybody else.

References

  1. Brennan AT, Bonawitz R, Gill CJ, et al. A meta-analysis assessing all-cause mortality in HIV-exposed uninfected compared with HIV-unexposed uninfected infants and children. AIDS. 2016;30:2351–2360. doi:10.1097/QAD.0000000000001211 ↩
  2. Slogrove AL, Goetghebuer T, Cotton MF, Singer J, Bettinger JA. Pattern of infectious morbidity in HIV-exposed uninfected infants and children. Frontiers in Immunology. 2016;7:164. doi:10.3389/fimmu.2016.00164 ↩
  3. Brennan AT, Bonawitz R, Gill CJ, et al. A meta-analysis assessing diarrhea and pneumonia in HIV-exposed uninfected compared with HIV-unexposed uninfected infants and children. Journal of Acquired Immune Deficiency Syndromes. 2019;82(1):1–8. doi:10.1097/QAI.0000000000002097 ↩
  4. Wedderburn CJ, Evans C, Yeung S, et al. Growth and neurodevelopment of HIV-exposed uninfected children: a conceptual framework. Current HIV/AIDS Reports. 2019;16:501–513. doi:10.1007/s11904-019-00459-0 ↩
  5. le Roux SM, Abrams EJ, Donald KA, et al. Infectious morbidity of breastfed, HIV-exposed uninfected infants under conditions of universal antiretroviral therapy in South Africa: a prospective cohort study. The Lancet Child & Adolescent Health. 2020;4(3):220–231. doi:10.1016/S2352-4642(19)30375-X ↩
  6. Goetghebuer T, Smolen KK, Adler C, et al. Initiation of antiretroviral therapy before pregnancy reduces the risk of infection-related hospitalization in human immunodeficiency virus-exposed uninfected infants born in a high-income country. Clinical Infectious Diseases. 2019;68(7):1193–1203. doi:10.1093/cid/ciy673 ↩
  7. Dubois MM, Jao J, Sun S, et al. Infectious morbidity and all-cause mortality of infants HIV-exposed uninfected compared to infants HIV-unexposed uninfected in Botswana. The Pediatric Infectious Disease Journal. 2025;44(3):214–216. doi:10.1097/INF.0000000000004603 ↩
  8. Touangnou-Chamda SA, Netongo PM, Njiki Bikoï J, et al. Impaired clinical, biological, and cytokine patterns in HIV-1 exposed uninfected newborns in Yaoundé: a comparative study of neonatal immune vulnerability. African Journal of Laboratory Medicine. 2026;15(1):3035. doi:10.4102/ajlm.v15i1.3035 ↩
  9. Djounda R, Ngamaleu MR, Honore A, et al. Growth, infection, and humoral immunity in children who are HIV exposed and uninfected. Frontiers in Cellular and Infection Microbiology. 2026;16:1816838. doi:10.3389/fcimb.2026.1816838 ↩
  10. Li X, Cao Y, Zou J, et al. Longitudinal trajectories of growth and development in HIV-exposed uninfected children from a long-term birth cohort — 8 regions, 3 PLADs, China, 2017–2024. China CDC Weekly. 2026;8(10):268–275. doi:10.46234/ccdcw2026.043 ↩
  11. Tchakoute CT, Sainani KL, Osawe S, et al. Breastfeeding mitigates the effects of maternal HIV on infant infectious morbidity in the Option B+ era. AIDS. 2018;32:2383–2391. doi:10.1097/QAD.0000000000001974 ↩
  12. Ásbjörnsdóttir KH, Slyker JA, Maleche-Obimbo E, et al. Breastfeeding is associated with decreased risk of hospitalization among HIV-exposed, uninfected Kenyan infants. Journal of Human Lactation. 2016;32(3):NP61–NP66. doi:10.1177/0890334415607854 ↩
  13. Bork K, Cames C, Cournil A, et al. Infant feeding modes and determinants among HIV-1-infected African women in the Kesho Bora Study. Journal of Acquired Immune Deficiency Syndromes. 2013;62(1):109–118. doi:10.1097/QAI.0b013e318277005e ↩
  14. Lwanga C, Aber P, Tickell KD, et al. Impact of HIV exposure without infection on hospital course and mortality among young children in sub-Saharan Africa: a multi-site cohort study. BMC Medicine. 2024;22(1):573. doi:10.1186/s12916-024-03790-5 ↩
  15. Ntuli L, Mtshali A, Mzobe G, Pillay N, Happel AU, Ngcapu S. Developmental challenges in infants who are HIV-exposed uninfected. Brain, Behavior, and Immunity. 2025;130:106078. doi:10.1016/j.bbi.2025.106078 ↩
  16. Salvi M, Fioretti B, Alberti M, et al. Understanding HIV-exposed uninfected children: a narrative review. Viruses. 2025;17(3):442. doi:10.3390/v17030442 ↩
  17. Condo JU, Gage A, Mock N, Rice J, Greiner T. Sex differences in nutritional status of HIV-exposed children in Rwanda: a longitudinal study. Tropical Medicine & International Health. 2015;20(1):17–23. doi:10.1111/tmi.12406 ↩