HIV in children and mother-to-child transmission

• HIV in children comes almost entirely from mother-to-child transmission (in utero, intrapartum or through breast milk). Without intervention 15 to 45% of infants acquire it; on maternal ART with viral suppression perinatal transmission is under 1%.^[8][6]
• Infants below 18 months cannot be diagnosed with antibody tests; virologic (PCR) testing is required, a first positive result is repeated, and ART is started immediately.- Early ART reduced early infant mortality by 76% in the CHER trial.^{[7] [5]}

By the end of this page you should be able to:

1. Explain how HIV passes from mother to child and why the timing of transmission matters.
2. Describe the schedule of infant virologic testing and the criteria for presumptively and definitively excluding HIV in an infant.
3. Choose a neonatal prophylaxis regimen based on the infant's risk category and the mother's virologic status.
4. State when to start ART in an infant with confirmed or presumptive HIV, with the evidence for early treatment.
5. Advise a mother living with HIV about feeding, contrasting formula with supported breastfeeding and the monitoring each requires.
6. Plan PMTCT before and during pregnancy, at delivery and postpartum.

A mother-to-child (vertical) transmission of HIV is infection of an infant acquired from the mother during pregnancy (in utero), during labour and delivery (intrapartum), or after birth through breast milk. This page focuses on children with perinatal HIV exposure and children living with HIV. Adults with HIV are covered in the page "HIV infection and AIDS", which also covers opportunistic prophylaxis, PrEP and PEP. This topic draws on the WHO consolidated HIV guidelines of 2021, the WHO clinical management update of December 2025, which revised postnatal prophylaxis and breastfeeding guidance for infants at risk, and, for the United Kingdom, the BHIVA pregnancy guidelines of 2025.^[1][3][4]

• Without intervention, 15 to 45% of infants born to women living with HIV acquire the infection; about 15 to 25% of that risk is attributed to breastfeeding. A 2021 WHO policy brief estimates that about half of all vertical transmission occurs during breastfeeding.^[8][2]
• About 85% of pregnant women living with HIV are on ART; roughly 150,000 infants acquired HIV through vertical transmission in 2020, most because mothers were undiagnosed, untreated or lost to care.- In well-resourced settings with universal antenatal testing and ART, perinatal infections have fallen to very low levels, because maternal ART suppresses the virus and infant prophylaxis covers residual risk. ^[2]

The risk to the infant rises with maternal viral load, absence or inadequacy of maternal ART, feeding without suppression, and acute maternal infection acquired late in pregnancy or while breastfeeding.

• Untreated maternal HIV is the strongest risk factor; perinatal infection is reported as virtually zero when ART is established before conception and viral load is under 50 copies/mL at delivery.^[2]
• Viraemia of 50 copies/mL or more in the 4 weeks before delivery moves an infant into the high-risk category for in utero and intrapartum acquisition.- Acute infection during pregnancy or breastfeeding carries high transmission risk because viral load is very high before the immune response matures. ^[6]
• Premastication (chewing or pre-warming food in an adult's mouth before feeding an infant) and unsafe feeding practices can also transmit HIV.

Transmission has three windows: during pregnancy in utero, during labour and delivery (especially with early membrane rupture or prolonged labour), and after birth through breast milk, whose risk accumulates with each month of feeding. Maternal ART that suppresses viral load below 50 copies/mL acts at every window, and the drug the infant receives adds a further safety margin. Prolonged viraemia destroys CD4 T cells and damages the brain, while early suppression preserves immune function and neurodevelopment; in the CHER trial early ART cut early infant mortality by 76% and HIV progression by 75% compared with deferred therapy.^[7]

Infants with HIV can be well at birth; symptoms, when they develop, are non-specific. Features that should prompt testing even without known exposure include recurrent or severe infections (pneumonia, persistent thrush, chronic diarrhoea), failure to thrive, persistent oral or oesophageal candidiasis, severe skin infections, or disseminated cytomegalovirus or Pneumocystis pneumonia in the first months of life. In older children and adolescents, HIV presents like adult HIV infection (see "HIV infection and AIDS"): weight loss, chronic fever, lymphadenopathy, recurrent respiratory infections. Because little distinguishes HIV from common childhood illness, the diagnostic anchor is maternal HIV risk or a positive test rather than the clinical picture alone.

A positive test removes the differential; before diagnosis the table compares conditions that share features with untreated perinatal HIV.

Every infant at risk should be managed on the assumption that HIV is possible until testing has excluded it.

Above 18 months, diagnosis rests on HIV antibody or antigen/antibody tests. Below 18 months, maternal IgG crosses the placenta and makes antibody tests unreliable, so a virologic (nucleic acid) test is required: infant diagnosis by PCR.^[5]

• Which tests. Either a plasma or dried blood spot HIV RNA nucleic acid test or a qualitative HIV DNA test can be used; a positive result must be repeated on a new specimen as soon as possible to confirm it.
• When. US panels recommend nucleic acid testing at birth, 14 to 21 days, 1 to 2 months and 4 to 6 months. Birth testing is not necessary for an infant at low risk who is not breastfed, but is recommended in low-risk infants who will be breastfed. For breastfed infants, testing is at least every 3 months during breastfeeding, and at 4 to 6 weeks and again 3 months after breastfeeding stops. ^[5]
• Confirmatory testing. A positive test is repeated, and ART is started immediately while awaiting confirmation; do not delay ART for the second result. ^[5]
• Excluding infection. HIV can be presumptively excluded in a non-breastfed infant with two negative virologic tests (one at 2 weeks or older and one at 4 weeks or older, at least 2 weeks after stopping infant prophylaxis), or one negative test at 8 weeks at least 2 weeks after stopping prophylaxis, or one negative antibody test at 6 months. Definitive exclusion requires two negative virologic tests, one at 1 month or older and one at 4 months or older (or two negative antibody tests on separate specimens at 6 months or older in infants not breastfed). A breastfed infant needs the full breastfeeding and post-cessation schedule. ^[5]
• Late presentation. Any child with signs suggesting HIV, even without documented exposure, should be tested.

• Maternal viral load is measured in pregnancy (early, around the third to sixth months, at 36 weeks, and at delivery if risk is high) and during breastfeeding, so infant management tracks the true risk. BHIVA recommends monthly viral load testing for mother and infant during breastfeeding and for 2 months after stopping. ^[4]
• CD4 count in the infant guides staging and prophylaxis against opportunistic infection.
• HIV RNA in the infant after starting ART confirms suppression.

An infant diagnosed and treated early may be seronegative at around 2 years. BHIVA recommends HIV antibody testing to detect seroreversion at 24 months, or at a minimum 8 weeks after breastfeeding stops if that is later. Because antibody tests can be misleading after early ART, the diagnosis of a treated child rests on the nucleic acid test history. ^[4]

There is no score that grades perinatal HIV itself. Severity is conveyed by age and two numbers:

• Age under 18 months with perinatal exposure defines the window in which nucleic acid testing is required.
• HIV RNA under 50 copies/mL in the mother from 20 weeks of gestation through delivery defines low risk of in utero and intrapartum acquisition; viraemia of 50 copies/mL or more in the 4 weeks before delivery defines high risk. ^[6]
• Markers of high transmission risk include acute maternal HIV infection, maternal ART resistance or interruption, spontaneous rupture of membranes or prolonged rupture-delivery interval with viraemia, and prematurity.

Every decision follows one principle: suppress the mother's virus as early and as completely as possible, then cover the infant for the residual risk. Nothing below should be read as a licence to delay maternal ART.

• Test all pregnant women for HIV early in pregnancy, and again in the third trimester when risk continues or risk factors exist.
• Start ART as soon as HIV is diagnosed, at any gestation. BHIVA recommends starting in the first trimester if the viral load is over 100,000 copies/mL or the CD4 is under 200 cells per microlitre, and that all women commence ART by week 24 at the very latest. WHO likewise recommends initiating ART urgently, even late in pregnancy.^[4][2]
• Check for resistance, interactions and adherence whenever viral load is detectable. At 36 weeks, BHIVA recommends optimising the regimen (including dolutegravir), resistance testing where appropriate, weekly viral loads and directly observed therapy. If viraemia persists at delivery, BHIVA recommends an optimised three-drug regimen including dolutegravir, with double-dose tenofovir and single-dose nevirapine, in close liaison with obstetrics.

• Vaginal delivery is supported when viral load is under 50 copies/mL in the absence of obstetric contraindications; vaginal birth after caesarean section is offered under the same condition.^[4]
• Caesarean section is planned when viral load is 50 to 399 copies/mL (taking into account duration on therapy, trajectory, adherence and obstetric factors) and is recommended at 400 copies/mL or more. ^[4]
• If the membranes rupture at term and viral load is 50 to 399 copies/mL, caesarean section is recommended; if viral load is 400 copies/mL or more, an urgent caesarean section is recommended, with delivery within 24 hours. ^[4]
• Intravenous zidovudine in labour is given when viral load is over 1000 copies/mL, or when it is unknown, starting 4 hours before planned caesarean section or on arrival in labour. ^[4]
• Delayed cord clamping is supported when viral load is under 50 copies/mL. ^[4]

All newborns exposed to HIV should receive antiretroviral drugs as soon as possible, preferably within 6 hours of birth. The regimen depends on the predicted risk of acquisition.^[6]

The table is a practical summary rather than a protocol; national programmes differ. Where presumptive HIV therapy is used, zidovudine should be continued alone to complete a total of 6 weeks if the three-drug course is shorter. Infants at high risk also need follow-up testing to exclude infection, and Pneumocystis jirovecii pneumonia prophylaxis (trimethoprim-sulfamethoxazole) from 4 to 6 weeks of age unless HIV has been presumptively excluded. ^[6]

Cure is not possible with current drugs, but suppression is. The goal is to start combination ART as early as possible.

• Start ART as soon as the first positive nucleic acid test is known, even before the confirmatory result returns, because delaying costs lives. Early ART reduced early infant mortality by 76% and HIV progression by 75% compared with waiting, as shown in the CHER trial.^[7]
• Preferred initial therapy for infants under 30 days of age in 2026 guidance is dolutegravir, the second-generation integrase inhibitor, with zidovudine plus lamivudine or emtricitabine as the nucleoside backbone.
• Dosing is by weight band and gestational age, with syrup or dispersible tablets used rather than adult formulations; many centres in resource-limited settings use fixed-dose combinations.
• Follow-up includes monitoring HIV RNA, CD4, growth, development and drug side effects.
• Cotrimoxazole prophylaxis is given to all infants living with HIV until immune reconstitution is confirmed, and to exposed infants at risk as above.
• Early ART also has a neurodevelopmental benefit: in CHER, infants who started ART before 3 months had significantly better motor and general developmental scores at 11 months than infants whose treatment was deferred.

This is the area where guidelines disagree most.

High-resource (BHIVA) position. Exclusive formula feeding removes all postnatal risk of HIV transmission, so BHIVA recommends that women feed with formula (or other suitable alternatives) exclusively, with support including free formula and equipment, and with cabergoline offered to suppress lactation when formula is chosen. When breastfeeding is chosen by a woman on ART with viral load under 50 copies/mL, BHIVA supports and monitors it, with the following rules:^[4]

• Advise that pregnancy and postpartum ART reduces but does not abolish transmission: the estimated risk on suppressive ART is 3 per 1000 infants at 6 months and 7 per 1000 at 12 months. ^[4]
• Breastfeed for no longer than about 6 months, then switch to formula with solids introduced normally.
• Feed exclusively: no formula mixed with breast milk and no water, tea, juice or solids before 6 months, because mixed feeding increases transmission risk. ^[4]
• Stop breastfeeding at once and start infant PEP if maternal viral load reaches 50 copies/mL or more while breastfeeding. ^[4]
• Test the infant monthly during and for 2 months after breastfeeding.
• Manage gastrointestinal illness aggressively and do not resume breastfeeding after it.
• Cabergoline suppresses lactation when breastfeeding is not being used.

Global (WHO) position. For settings where formula and safe water cannot be guaranteed, WHO recommends lifelong maternal ART with supported adherence and exclusive breastfeeding for 6 months, followed by complementary feeding with continued breastfeeding up to 2 years, for mothers with suppressed viral load. About 85% of pregnant women living with HIV are on ART, and close to half of all vertical transmission now occurs during breastfeeding, mainly because of late maternal diagnosis or loss of adherence rather than breast milk itself. ^[2]

United States (HHS) position. As of 2024 the US perinatal panel supports shared decision making: replacement feeding with commercial formula or pasteurised donor human milk eliminates postnatal risk, but patients on ART with a sustained viral load under 50 copies/mL who choose to breastfeed should be supported with monthly viral load checks and infant testing every 3 months, and breastfeeding stopped if viraemia appears. HHS notes that viral suppression decreases breastfeeding transmission risk to less than 1% but not zero.

Untreated perinatal HIV is usually fatal within the first 2 years of life. Even in treated infants there are risks to monitor:

• Immunodeficiency and opportunistic infections (Pneumocystis pneumonia, cytomegalovirus, tuberculosis, chronic candidiasis).
• Neurodevelopmental delay and HIV encephalopathy, attenuated but not eliminated by early ART.
• Drug toxicity (zidovudine-related anaemia, nevirapine hepatotoxicity), usually managed by substitution rather than stopping treatment.
• Failure to thrive and chronic lung disease from recurrent infections.
• Disclosure, adherence and mental health challenges in adolescence, plus transition to adult services.

With early diagnosis, ART and cotrimoxazole, perinatal HIV is a chronic manageable condition with excellent long-term outcomes. Early ART begun in the first 12 weeks reduced early mortality by 76% in CHER; infants on ART reached virologic suppression and grew normally when adherence was maintained.

• Antenatal screening: universal opt-out HIV testing in pregnancy, with repeat testing in the third trimester in high-prevalence areas or ongoing risk.
• Pre-conception counselling: in BHIVA this starts before conception, including resistance review and regimen choice during pregnancy.
• Preventing acquisition by the mother while breastfeeding: post-exposure prophylaxis after a significant exposure; PrEP now an option during pregnancy and breastfeeding in US guidance for at-risk women, including long-acting injectable agents.
• Infants with exposure after birth (premastication, maternal seroconversion during breastfeeding, sexual abuse) need additional testing with antibody or nucleic acid tests based on age, and consideration of 4-week three-drug prophylaxis when new viraemia arises.
• Premature or sick neonates require neonatal doses by gestational age and close liaison with paediatric HIV services; congenital CMV screening and hepatitis B immunoglobulin are co-administered.

• A single dried blood spot and point-of-care nucleic acid testing shorten turnaround from weeks to same-day, making same-day ART initiation feasible where centralised laboratory delays have historically cost infant lives.
• Where PCR capacity is limited, prioritise testing at 6 weeks and whenever an exposed infant is unwell; WHO recommends that no infant reach the second year without their HIV status being established by 18 months at the latest.
• If maternal ART is unavailable or interrupted, immediate initiation or restart at the earliest antenatal contact is the single most effective intervention, because suppressing viral load before delivery removes most transmission risk.
• Exclusive breastfeeding for 6 months with lifelong maternal ART is the safest feeding policy in low-resource settings; WHO's rationale is that the survival benefits of breastfeeding outweigh the small residual transmission risk on suppressed ART.
• Infection control: universal precautions, screening of blood products and safe needle practice.

• Every pregnant woman or birthing parent with HIV, and every infant exposed to HIV, needs care shared between obstetrics, paediatric HIV and adult HIV services.
• Refer urgently when an exposed infant is unwell, has respiratory distress or temperature, or fails to thrive, because Pneumocystis or CMV pneumonia can be the first presentation.
• Refer for genotype resistance testing whenever transmission occurs despite ART, or when maternal viral load fails to fall on treatment.
• Transfer to adult HIV services should be planned in adolescence, with early introduction of the young person as their own decision-maker.

• With modern treatment a mother living with HIV can have a healthy pregnancy and a healthy child; perinatal transmission on suppressed therapy is close to zero.
• Feeding decisions (formula versus breastfeeding) should be discussed early, non-judgementally and more than once, using written information.
• Cotrimoxazole prophylaxis, immunisations according to national schedules, growth monitoring and developmental follow-up are part of routine care for all exposed children.

• HIV infection and AIDS (infectious-disease): adult disease, ART, opportunistic prophylaxis, PrEP and PEP.
• Childhood pneumonia and failure to thrive: common presentations in untreated perinatal HIV.
• Neonatal resuscitation and sepsis: immediate newborn care in infants exposed to HIV.
• Antenatal screening and reproductive health topics.
• Infant feeding and colic: practical feeding support for families on formula.