Manage HIV in pregnancy, labour and the puerperium, and prevention of vertical transmission (PVT)

In one line

HIV in pregnancy is managed as one problem with two patients: the mother, whose own survival depends on lifelong dolutegravir-based ART and aggressive screening for tuberculosis, and the infant, whose freedom from infection is bought almost entirely by driving and holding the maternal viral load below detection across pregnancy, delivery and breastfeeding. Prevention of vertical transmission (PVT — the term that replaced PMTCT in South African practice) is, at its core, viral-load control plus risk-stratified infant prophylaxis, and South Africa has taken vertical transmission from roughly one in four exposed infants to under one in a hundred near birth on exactly that principle.

The mechanics of a positive antenatal HIV test, the basic ART regimen and routine booking bloods are assumed groundwork — covered as a booking diagnosis at the Intermediate level. The consultant layer is reasoning about viral-load–driven risk: the woman who arrives in labour unbooked, the unsuppressed mother near term, infant feeding under suppressive ART, and how to argue any of it from the data. The gynaecological HIV interface — genital TB, cervical disease, opportunistic infection — sits in genital-tb-hiv-gynaecology.

Mechanism & pathophysiology

Vertical transmission happens across three windows, and each maps to a different mechanism, which is why a single intervention does not cover all of them.

Intrauterine transmission (roughly the minority of in-utero infections, occurring mostly in late pregnancy) is transplacental: cell-free and cell-associated virus crosses a placenta whose integrity is itself degraded by maternal viraemia, chorioamnionitis, placental malaria and co-infections. Intrapartum transmission — historically the largest single contributor in a non-breastfeeding, untreated population — is exposure of the infant to maternal blood and genital-tract secretions during labour and delivery, amplified by ruptured membranes, instrumentation, and a high genital-tract viral load. Postnatal transmission is through breast milk, a continuous low-grade exposure that accumulates over the whole duration of breastfeeding; in a breastfeeding population it becomes the dominant route, and in South Africa more than 80% of the residual transmissions now occur during the first six months of breastfeeding.

The single variable that runs through all three windows is the maternal HIV viral load. Risk is not a step function tied to a diagnosis; it is continuous and steeply dose-dependent on the number of circulating virions the infant is exposed to. The 2025 Lancet meta-analysis of 147 studies quantified this with precision: pooled perinatal transmission was 0.2% with a maternal viral load below 50 copies/mL, 1.3% at 50–999, and 5.1% at ≥1000 copies/mL — an adjusted relative risk of 22.5 for the highest band versus the suppressed band. The same gradient holds postnatally, where monthly breastfeeding transmission was 0.1% with a recent viral load under 50 and 0.5% at ≥50. This is the molecular logic of PVT in one sentence: drive the viral load down and hold it there, and the exposure across every window collapses toward zero.

That gradient also explains why timing of suppression matters as much as the fact of it. A woman established on ART and virally suppressed before conception enters pregnancy with the placenta never exposed to high-titre virus; the Lancet analysis found zero perinatal transmissions among 4675 women on pre-conception ART with a viral load below 50 near birth — the strongest available evidence that the "undetectable equals untransmittable" principle extends to pregnancy and birth. The newly-diagnosed woman starting ART in the third trimester, by contrast, may not reach undetectable before she delivers, so her placenta and genital tract have been exposed to viraemia for months and she may still be unsuppressed intrapartum. Two women with the same final regimen can carry an order-of-magnitude difference in transmission risk purely on when suppression was achieved. The postnatal window is the one place where even suppression is not demonstrably zero-risk: the Lancet pooled estimate at recent viral load <50 was very low but not nil, and the authors were explicit that current data — largely from cohorts without frequent viral-load monitoring or modern regimens — are insufficient to claim true U=U during breastfeeding. That residual uncertainty is precisely what the infant-prophylaxis layer exists to cover.

The immunological backdrop is that pregnancy is a state of relative immune modulation, and untreated HIV strips the maternal reserve further. A low CD4 count is less about transmission risk per se (viral load drives that) and more about the mother's own vulnerability — to tuberculosis above all, but also to pneumonia, cryptococcal disease and the opportunistic infections that have made non-pregnancy-related infection the leading driver of HIV-associated maternal death in South Africa. Treating the mother and protecting the infant are therefore not competing goals; the same suppressive ART does both.

One mechanistic subtlety has practical force at the breastfeeding interface: breast inflammation raises the milk viral load even when the plasma viral load is suppressed. Mastitis, a cracked nipple, a breast abscess or subclinical inflammation locally disrupts the blood–milk barrier and lets cell-associated virus into the milk compartment, which is why breast pathology in a lactating woman living with HIV is treated promptly rather than conservatively, and why mixed feeding is discouraged — non-human feeds injure the infant gut mucosa and create a portal for whatever virus is present. Suppression lowers the milk viral load; protecting the breast and the infant gut closes the remaining gaps.

Assessment

The assessment separates cleanly into screening the population, and then placing the individual woman onto one of three management pathways.

Universal antenatal testing, and re-testing through the at-risk window.

• HIV testing is offered to every woman at the first antenatal visit (provider-initiated, opt-out), with same-day result and same-day ART for those who test positive.
• In a high-incidence setting a single negative booking test is not enough — maternal seroconversion during pregnancy or breastfeeding is a recognised and high-risk transmission route (the mother seroconverts with a very high viral load and no prophylaxis in place). South African practice therefore re-tests the HIV-negative woman at every subsequent antenatal visit and three-monthly throughout breastfeeding. A woman who tested negative at booking but presents in labour or postnatally must be re-tested.
• The negative rapid test also has a false-negative trap in early seroconversion (window period) and in advanced disease; clinical suspicion overrides a single reassuring result.

Staging the individual: viral load and CD4 carry different information.

• The viral load is the transmission-risk variable and the treatment-success variable. It is checked at the start of ART, then on the schedule below, and it is the number that decides intrapartum and infant-feeding plans. A viral load ≥1000 copies/mL near delivery flags both a high-risk infant and likely treatment failure or non-adherence.
• The CD4 count stages the mother's own immune risk, not the infant's transmission risk. A CD4 below 200 mandates a deliberate search for, and prophylaxis against, opportunistic infection — cotrimoxazole prophylaxis, a reflex cryptococcal antigen test at the relevant threshold, and heightened TB vigilance.
• Tuberculosis screening is non-negotiable at every visit. TB is the leading infectious driver of maternal death in HIV-positive South African women; every pregnant woman living with HIV is symptom-screened (cough, fever, night sweats, weight loss) at each contact, investigated where positive, and offered TB preventive therapy where active disease is excluded.
• Co-infection screening completes the picture: syphilis (RPR, with the renewed national concern over congenital syphilis — a co-epidemic that shares the same antenatal-screening machinery as HIV and is folded into the triple-elimination agenda), hepatitis B (HBsAg — relevant to both the maternal regimen, since tenofovir and lamivudine are active against hepatitis B, and the infant's birth-dose vaccine), and cervical screening, since HIV accelerates cervical carcinogenesis.
• Advanced HIV disease (CD4 <200, or a WHO clinical stage 3/4 condition) reframes the woman as critically ill, not merely pregnant. She needs the advanced-disease package — cryptococcal antigen screening with pre-emptive treatment where positive, cotrimoxazole prophylaxis, intensified TB investigation including urine lipoarabinomannan where available — alongside her ART, because the immediate threat to her life is the opportunistic infection, not the obstetrics. The danger is anchoring on the pregnancy and missing the failing immune system behind it.

The three pathways — identify which one the woman is on, because management diverges from here.

Almost every consultant-level decision in HIV-PVT follows from correctly placing the woman in this table, because her infant's risk category, her intrapartum plan and her infant's prophylaxis all flow from it.

Management

Structure the plan immediate → ongoing → long-term, and let the maternal viral load drive every branch.

Immediate — start (or continue) suppressive ART

Every pregnant woman living with HIV is on lifelong ART; there is no longer a "treat for the baby then stop" framing. The South African preferred first-line regimen is the fixed-dose combination tenofovir disoproxil fumarate + lamivudine + dolutegravir (TLD), one tablet daily, for all adults and adolescents including pregnant women. Dolutegravir is the deliberate choice: a high genetic barrier to resistance, rapid viral-load decline (valuable when there is little time before delivery), excellent tolerability, and — crucially for this population — no increased risk of neural-tube defects, the concern that once destabilised first-line choice and has since been resolved (developed below). The newly diagnosed woman starts the same day or within two weeks; pregnant women are a priority group for rapid initiation precisely because every week of viraemia is exposure.

A renal check (the SA threshold for tenofovir use in pregnancy is a serum creatinine below 85 µmol/L) precedes or accompanies initiation; note that dolutegravir itself raises serum creatinine by under 15% by blocking tubular secretion without harming glomerular filtration — an expected change, not a reason to withhold the drug.

Ongoing — viral-load monitoring and the unsuppressed mother

The viral-load schedule is the spine of antenatal HIV care:

• Already on ART before pregnancy: viral load at the first antenatal visit, then on the routine schedule, to confirm she is and stays suppressed.
• Newly initiated in pregnancy: viral load three months after starting, then six-monthly — and always a viral load near term to assign the infant's risk category.

A raised or unsuppressed viral load (≥50, and especially ≥1000 copies/mL) is the antenatal emergency that is easy to under-react to. Because dolutegravir resistance is genuinely rare, the overwhelmingly likely cause is suboptimal adherence, and the response is a structured assessment — adherence support and enhanced counselling, a check for drug interactions (rifampicin is the classic culprit, below), confirmation she is actually taking the regimen — followed by a repeat viral load. Switching regimens reflexively for an unsuppressed result on a DTG-based regimen is usually the wrong move; fixing adherence is usually the right one. The clock matters: a woman found unsuppressed at 34 weeks needs the adherence problem solved now, because the target is to suppress her before she delivers and certainly before sustained breastfeeding.

Intrapartum — the plan falls out of the viral load

• Suppressed (VL <1000, ideally <50): the mode of delivery is decided on obstetric grounds alone. A suppressed woman delivers vaginally; HIV is not an indication for caesarean section, and avoiding an unnecessary caesarean spares her the markedly higher infective and anaesthetic morbidity that HIV and a low CD4 add. She continues her ART through labour without interruption. Routine artificial rupture of membranes and instrumentation are avoided where they add nothing, but a suppressed viral load makes the genital-tract exposure trivial.
• Unsuppressed or unknown (VL ≥1000, or no recent result): here the genital-tract viral load is the threat, and the considerations shift — continue/optimise ART, minimise prolonged rupture of membranes and avoidable instrumentation, and weigh caesarean section for a genuinely high viral load near term as one (imperfect, late) lever among several. The more important truth is that an elective caesarean is a weak substitute for the suppression that should have been achieved antenatally; it reduces intrapartum exposure but does nothing for the breastfeeding window, and a well-suppressed vaginal delivery beats an unsuppressed caesarean.

The woman who presents unbooked in labour

This is the highest-yield emergency scenario, because there is no time to suppress before delivery, so the whole plan compresses into intrapartum prophylaxis plus a high-risk infant. The South African protocol for a woman diagnosed with HIV during labour is a stat single fixed-dose TLD tablet plus a stat single dose of nevirapine, then lifelong ART started the following day, a two-month ART supply at discharge, and explicit counselling on infant feeding, infant prophylaxis and follow-up infant testing. Her infant is, by definition, high-risk and receives enhanced prophylaxis. The same logic — test, treat immediately, treat the infant as high-risk — applies to any woman with unknown or untreated status at the point of delivery.

Infant prophylaxis — risk-stratified, and the part candidates muddle

Infant prophylaxis is stratified by the infant's transmission risk, which is defined by the maternal viral load and ART status, not given as one blanket regimen:

The infant is then tracked by HIV PCR at birth, at 10 weeks and at 6 months, with a further test six weeks after breastfeeding stops and a confirmatory HIV antibody test at 18 months. The high-risk breastfed infant's nevirapine runs longer and is explicitly tethered to documented maternal suppression — a neat expression of the whole PVT logic, that the infant's protection is titrated to the mother's viral load.

Breastfeeding on suppressive ART — the South African recommendation

South African policy supports exclusive breastfeeding for women on ART, on the evidence that breastfeeding under suppressive ART carries a very low transmission risk that is heavily outweighed — in this setting — by the survival, nutritional and infectious-disease benefits of breast milk and the hazards of unsafe formula feeding. The counselling is specific: breastfeed exclusively (mixed feeding increases transmission risk by disrupting the gut mucosa), stay adherent and suppressed, and treat any breast pathology (mastitis, cracked nipples) promptly because inflammation raises milk viral load. The honest caveat from the latest evidence is that postnatal transmission on suppressive ART is very low but not provably zero, which is exactly why the suppressed mother's infant still gets six weeks of nevirapine and why three-monthly maternal re-testing continues through lactation.

Long-term — the puerperium and beyond

ART is lifelong and does not stop after delivery or weaning; the postnatal drop-off in adherence and viral suppression is a well-documented failure point and a target for active retention-in-care. Contraception is integrated into the same visit (dual method — a hormonal method or IUCD plus condoms), with a deliberate eye on the next pregnancy: the ideal is that the next conception happens with ART already established and the viral load already undetectable, which is the configuration associated with zero perinatal transmission. The mother's own chronic-disease care — TB surveillance, cervical screening, CD4-guided opportunistic-infection prophylaxis — continues, because PVT that saves the infant but loses the mother to undiagnosed TB has failed half its mandate.

Two drug interactions worth knowing precisely

• Rifampicin–dolutegravir. Rifampicin (in TB treatment, and the co-infected pregnant woman is common in South Africa) induces dolutegravir metabolism and halves its exposure. The fix is to double the dolutegravir dose to 50 mg twelve-hourly — practically, add a separate DTG 50 mg tablet twelve hours after the daily TLD dose — for the duration of rifampicin co-treatment, then revert. Missing this interaction can drive the woman unsuppressed precisely when she is sickest.
• Dolutegravir and hormonal contraception. Dolutegravir does not meaningfully reduce hormonal-contraceptive efficacy (it is the older efavirenz that lowered etonogestrel-implant levels), so the integrase-inhibitor era has simplified contraceptive counselling — implants, injectables, oral methods and IUCDs are all options alongside condoms.

Guidelines compared

The South African and WHO positions are closely aligned — universal lifelong dolutegravir-based ART for all pregnant women, with viral load as the central monitoring tool — and the differences are of emphasis and operational detail rather than principle.

The most important recent change is the rename and reframe to PVT, which is more than cosmetic: it reflects the shift from a vertical "mother-to-child" framing toward a model in which the woman's own lifelong treatment is the primary intervention and the prophylaxis is a risk-stratified backstop. The other live difference is the elimination scaffolding: WHO's validation of elimination of vertical transmission uses a triple-elimination framework (HIV, syphilis, hepatitis B) with tiered certification and impact targets — a vertical-transmission rate below 5% in breastfeeding populations (or below 2% in non-breastfeeding populations) and at most 50 new paediatric infections per 100,000 live births. South Africa has reached the lower-tier impact target with an overall vertical-transmission rate under 5% but has not yet achieved full validation, and closing the residual gap — concentrated in maternal seroconversion during pregnancy/breastfeeding and in postnatal transmission — is the explicit national programme goal.

The evidence & the controversy

Three threads define the modern PVT conversation, and a candidate should be able to argue all three.

Does U=U hold in pregnancy? For sexual transmission, sustained suppression means zero transmission — settled. The question for obstetrics was whether the same is true vertically, and the 2025 Lancet meta-analysis is the most authoritative answer to date. Across 147 studies it found perinatal transmission of ≤0.2% with a maternal viral load under 50, and — the headline — zero transmissions among 4675 women on pre-conception ART with an undetectable viral load near birth. The defensible reading is that U=U applies to perinatal transmission for women suppressed before and through pregnancy, which is a powerful counselling message and a powerful argument for getting women onto ART before they conceive. The honest limit, which the authors stressed and which an examiner will probe, is the breastfeeding window: postnatal transmission at viral load <50 was very low but not zero, and the data are too sparse (few cohorts with frequent viral-load monitoring on modern regimens) to claim U=U during lactation. So the message is calibrated — undetectable means untransmittable around birth; during breastfeeding it means very low risk, not no risk, which is why prophylaxis and monitoring persist.

The dolutegravir neural-tube-defect story — a case study in reading a safety signal. When the Tsepamo surveillance study in Botswana first reported, periconception dolutegravir was associated with neural-tube defects in about 0.94% of exposures versus 0.1% on other ART — a frightening signal that prompted programmes worldwide to restrict dolutegravir in women of reproductive potential. By the time the fuller 2019 analysis was published, the rate had fallen to 0.30% with DTG at conception (5 in 1683) versus 0.10% on non-DTG ART — still a statistically significant excess of about 2 per 1000, but far smaller. With continued accrual the difference disappeared: updated estimates of roughly 0.10% on DTG versus 0.11% on other ART — no meaningful difference. A 2025 re-analysis made the methodological point explicit: the original signal was statistically compatible with a wide range of effect sizes including no effect, and under sequential monitoring the probability of "decision reversal" was high — in plain terms, the early alarm was largely statistical noise from small numbers. The consultant lesson is twofold: dolutegravir is now recommended for all women including periconception (South Africa's guidelines state no NTD restriction), and a tiny early safety signal on small numbers should be held with appropriate uncertainty rather than treated as established fact — a live theme in how regulators and clinicians handle interim data.

Where the residual transmissions now are, and what that implies. South Africa drove near-birth vertical transmission from roughly 23% in the early 2000s to around 0.7% by 2019, an extraordinary public-health achievement built on universal ART. But the cumulative 18-month transmission rate sits around 4.3%, because more than 80% of the remaining transmissions occur during breastfeeding, and a substantial share trace back to maternal seroconversion during pregnancy or lactation — a woman who tested negative at booking, was therefore on no treatment, and acquired HIV with a high viral load while breastfeeding. The implication reorders the priorities: the marginal gain is no longer in the antenatal clinic for already-positive women (that system works) but in re-testing through the breastfeeding window, sustaining postnatal adherence, and preventing maternal acquisition in the first place. This is why three-monthly re-testing and postnatal retention-in-care are not box-ticking but the actual frontier of elimination.

Landmark trials & key evidence

A worked figure to carry into a viva: moving a woman from a viral load of ≥1000 to <50 copies/mL takes the pooled perinatal transmission risk from 5.1% to 0.2% — an absolute risk reduction of about 4.9 percentage points, so roughly 20 women suppressed to prevent one perinatal infection (NNT ≈ 1/0.049 ≈ 20), before counting the breastfeeding window where suppression keeps paying. That single arithmetic is the whole case for viral-load–driven PVT.

Exam traps & red flags

• Treating CD4 as the transmission-risk number. It is not — the viral load drives transmission and assigns the infant's risk category; CD4 stages the mother's immune risk and her opportunistic-infection vulnerability. Conflating them misdirects the plan.
• Stopping ART after delivery or weaning. ART is lifelong. Postnatal adherence drop-off is a documented failure point and a leading source of late transmission and maternal harm — plan retention, don't assume it.
• Defaulting to caesarean section for HIV. A suppressed woman delivers vaginally on obstetric grounds; caesarean adds infective and anaesthetic morbidity for no transmission benefit. Caesarean for viral load is a weak, late lever and never substitutes for antenatal suppression — and it does nothing for the breastfeeding window.
• Switching regimen reflexively for an unsuppressed viral load on TLD. Dolutegravir resistance is rare; the cause is almost always adherence (or an unrecognised rifampicin interaction). Fix adherence and repeat the viral load before contemplating a switch.
• Missing the rifampicin–dolutegravir interaction. Rifampicin halves DTG exposure; the co-infected woman needs the DTG dose doubled (an extra 50 mg twelve hours after TLD) or she drifts unsuppressed exactly when TB makes her most fragile.
• Restricting dolutegravir over neural-tube-defect fear. That signal has resolved; SA and WHO recommend DTG for all women including periconception. Withholding it is now the error.
• A single negative booking test treated as definitive. In a high-incidence setting, maternal seroconversion in pregnancy or breastfeeding is a major residual transmission route — re-test at every antenatal visit and three-monthly through breastfeeding; re-test the unbooked woman in labour.
• Mixed feeding. Counselling "some breast, some formula" increases transmission by breaching the gut mucosa — the recommendation on ART is exclusive breastfeeding, not mixed.
• Forgetting TB. TB is the leading infectious cause of HIV-associated maternal death in South Africa; symptom-screen at every visit and treat or prevent. A PVT plan that ignores the mother's TB risk is incomplete.
• Giving every exposed infant the same prophylaxis. Infant prophylaxis is risk-stratified — low-risk infants get nevirapine for six weeks; high-risk breastfed infants get longer nevirapine (tied to maternal suppression) plus zidovudine. Treating a high-risk infant as low-risk undertreats the highest-exposure babies.

Evidence anchors

• Connor et al. — zidovudine reduces maternal–infant HIV transmission (ACTG 076), N Engl J Med 1994
• Zash et al. — Neural-tube defects and antiretroviral regimens in Botswana (Tsepamo), N Engl J Med 2019
• Brummel, Swanson, Caniglia, Lockman, Zash, Shapiro — embracing uncertainty in the Tsepamo safety signal, AIDS 2025
• Dugdale et al. — maternal viral load and perinatal/postnatal HIV transmission: systematic review and meta-analysis, Lancet 2025
• Guay et al. — single-dose intrapartum/neonatal nevirapine vs zidovudine cuts transmission 47% in a breastfeeding population (HIVNET 012), Lancet 1999
• Fowler et al. — antenatal combination ART vs zidovudine + single-dose nevirapine: lower transmission, higher perinatal toxicity (PROMISE), N Engl J Med 2016
• Kintu, Malaba et al. — dolutegravir vs efavirenz started in late pregnancy suppresses faster before delivery (DolPHIN-2), Lancet HIV 2020
• Moran & Moodley — the effect of HIV infection on maternal health and mortality, Int J Gynaecol Obstet 2012
• South Africa NDoH — 2023 ART Clinical Guidelines for the Management of HIV in Adults, Pregnancy and Breastfeeding, Adolescents, Children, Infants and Neonates (preferred first-line TLD; intrapartum diagnosis = stat TLD + stat nevirapine; rifampicin–DTG dose-doubling; the SA prevention-of-vertical-transmission framework).
• South Africa NDoH — National PVT / prevention-of-vertical-transmission guideline: infant risk stratification (low-risk = maternal VL <1000 at delivery), risk-stratified infant nevirapine ± zidovudine, infant HIV PCR at birth / 10 weeks / 6 months and antibody at 18 months, maternal re-testing at every antenatal visit and three-monthly in breastfeeding.
• WHO — elimination of vertical transmission (triple-elimination) validation framework: vertical-transmission rate <5% (breastfeeding) or <2% (non-breastfeeding) and ≤50 new paediatric infections per 100,000 live births.