Describe HIV in pregnancy — its aetiology, clinical features and management.

ART reduces vertical transmission to under 2%.

Definition

Mother-to-child (vertical) transmission of HIV is the passage of infection from an HIV-positive mother to her baby, which can occur in utero, during labour/delivery, or through breastfeeding. With a full package of interventions the risk falls from ~25–35% to under 2%.

Measures to Prevent Transmission

• Maternal antiretroviral therapy — lifelong combination ART for every pregnant woman, started early and continued, to suppress the maternal viral load (the single most important measure).
• Mode of delivery — vaginal delivery is safe when the viral load is suppressed; elective caesarean section (before labour/rupture of membranes) when the viral load is high or unknown.
• Intrapartum care — avoid prolonged rupture of membranes, amniotomy, instrumental delivery, fetal scalp electrodes and episiotomy where possible; maternal antiretroviral cover in labour.
• Infant prophylaxis — antiretroviral drugs (e.g. Nevirapine ± zidovudine) to the newborn for the recommended period, with early infant testing.
• Infant feeding — exclusive replacement feeding when it is acceptable, feasible, affordable, sustainable and safe; otherwise exclusive breastfeeding with maternal ART (avoid mixed feeding).

A Note on WHY PPTCT Is One of the Great Successes

A useful point is understanding why mother-to-child transmission of HIV has been reduced so dramatically — from a natural rate of 25–40% to under 2% — and what makes this possible. Transmission occurs at three points: across the placenta in utero, during labour and delivery (the largest share, through contact with maternal blood and secretions), and through breastfeeding. Each can be attacked. The key insight is that the risk of transmission tracks the maternal viral load — so suppressing the virus with antiretroviral therapy removes the single greatest determinant of risk. Hence the strategy: universal antenatal HIV testing to identify infected mothers; lifelong ART for every HIV-positive pregnant woman, started as early as possible so that the viral load is undetectable by delivery; safe obstetric practice (avoiding unnecessary instrumentation, prolonged rupture of the membranes and invasive procedures, with elective caesarean only if the viral load remains high); infant antiretroviral prophylaxis (nevirapine) after birth; and a clear, supported infant-feeding choice — exclusive breastfeeding under maternal ART, since mixed feeding carries the highest risk. Understanding that suppressing the maternal viral load is the linchpin explains why 'test and treat' has made vertical transmission a largely preventable event.

• Vertical transmission occurs in utero, during labour/delivery (the largest share) and through breastfeeding — 25–40% without intervention, <2% with full PPTCT.
• The risk tracks the maternal viral load — so lifelong ART for every HIV-positive pregnant woman is the cornerstone.
• Universal (opt-out) antenatal HIV testing is essential to identify mothers who can be treated.
• Obstetric care: avoid prolonged rupture of the membranes, invasive procedures and unnecessary instrumentation; elective caesarean if the viral load is high.
• Infant: antiretroviral prophylaxis (nevirapine) after birth; exclusive breastfeeding under maternal ART — mixed feeding carries the highest risk.