HIV in pregnancy and prevention of transmission

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Vertical HIV transmission can occur in utero, during labour and delivery or through breast milk. Without intervention risk is substantial, but maternal ART, sustained viral suppression, planned birth and neonatal prophylaxis reduce UK transmission to very low levels.

The maternal health indication for lifelong ART is primary. Regimens are selected for potency, resistance barrier, placental and fetal evidence, hepatitis B activity, renal function, tolerability and interactions with supplements and obstetric medicines.

Viral load near delivery is the key modifiable predictor. The delivery pathway distinguishes below 50, 50 to 399 and 400 copies/mL or higher, while obstetric factors, adherence history, duration of suppression and preterm labour refine decisions.

Postnatal care continues prevention. Infant prophylaxis, virological testing and follow-up proceed through paediatric HIV services. Feeding discussions must be factual and non-coercive, acknowledging that formula eliminates postnatal exposure while supported breastfeeding is possible only under a strict suppressed pathway.

Key points

Offer HIV testing early in every pregnancy and repeat in later pregnancy when ongoing exposure or clinical risk warrants it.
Continue effective suppressive ART in someone already treated; avoid switching a stable regimen without a maternal, fetal or interaction reason.
Start a potent complete ART regimen promptly after a new diagnosis, using resistance, hepatitis B, gestation and comorbidity to select drugs.
Measure viral load throughout pregnancy and at about 36 weeks because the late-pregnancy result determines delivery planning.
Planned vaginal birth is appropriate when viral load is below 50 copies/mL and no obstetric contraindication exists.
Consider individual factors when viral load is 50 to 399 copies/mL; recommend planned caesarean birth from 39 weeks when it is 400 copies/mL or higher.
Give neonatal prophylaxis as soon as possible, ideally within four hours of birth, with drug number and duration based on transmission risk.
Formula feeding eliminates breast-milk HIV transmission; supported breastfeeding requires sustained suppression, exclusive feeding and intensive monthly maternal and infant monitoring.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

In-utero transmission

Maternal viraemia crosses the placenta during pregnancy, especially with acute infection, advanced disease or placental inflammation.

Intrapartum exposure

Infant mucosa contacts maternal blood and genital secretions during labour, with risk determined largely by viral load.

Breast-milk transmission

Cell-free and cell-associated virus in breast milk can transmit postnatally when maternal suppression is absent or interrupted.

Acute maternal acquisition

Primary infection during pregnancy or breastfeeding produces very high viral burden before antibodies and treatment control develop.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Placental barrier breach
Placental inflammation, maternal viraemia and microtransfusion can expose fetal target cells to HIV before birth, particularly when viral suppression is incomplete.
2
Mucosal exposure at birth
Prolonged contact with infected blood and secretions permits virus entry across neonatal oral, ocular and gastrointestinal mucosa.
3
Viral suppression
Maternal ART reduces plasma and genital viral burden, making fetal and neonatal exposure progressively less likely.
4
Neonatal post-exposure blockade
Prompt neonatal antiretroviral prophylaxis inhibits replication of virus acquired around birth before infection becomes amplified and stable cellular reservoirs are established.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Known suppressed HIV

A pregnant person already undetectable on tolerated ART usually continues treatment with interaction and pregnancy-safety review.

New antenatal diagnosisRed flag

A reactive screen requires urgent confirmation, baseline viral load and rapid specialist ART while emotional and safeguarding support begins.

Acute seroconversionRed flag

Fever, rash, pharyngitis and lymphadenopathy after pregnancy exposure may precede antibody positivity and requires HIV RNA.

Late-pregnancy viraemiaRed flag

Detectable viral load may reflect missed doses, vomiting, cation interaction or resistance and changes mode and timing of birth.

Unplanned labourRed flag

Labour or ruptured membranes before viral suppression and neonatal plans are documented requires immediate intrapartum risk management.

Postnatal feeding riskRed flag

Mastitis, cracked bleeding nipples, mixed feeding, infant oral disease or maternal rebound increases concern during breastfeeding.

Red flags requiring action

Acute HIV acquisition during pregnancy or breastfeeding produces high viraemia and a major transmission risk.
Viral load at or above 400 copies/mL near delivery generally requires planned caesarean birth and specialist intrapartum treatment from 39 weeks.
A rising or newly detectable viral load requires same-day adherence, interaction, resistance and delivery-plan review.
Preterm labour or ruptured membranes before the agreed plan needs immediate HIV maternity contact.
An infant whose prophylaxis is delayed, incomplete or based on missing maternal results requires urgent paediatric HIV review.
Breastfeeding with detectable maternal viral load, mastitis, breast abscess or infant oral inflammation requires immediate interruption and specialist assessment.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Confirmatory HIV test and HIV RNAFirst stepConfirmatory
Why
Confirm a reactive antenatal screen and detect acute infection during a serological window.
Interpretation and limitations
Do not communicate one reactive screen as definitive, but involve the HIV maternity team immediately while confirmation proceeds.
02
HIV viral load
Why
Measure treatment response and determine transmission and delivery risk throughout pregnancy.
Interpretation and limitations
Check at booking or diagnosis, after starting or changing ART, during pregnancy and near 36 weeks; repeat urgently when adherence or rebound is suspected.
03
CD4 count and resistance genotype
Why
Assess immune risk and identify transmitted or acquired resistance for a fully active regimen.
Interpretation and limitations
Take genotype before treatment where possible but do not delay rapid ART; low CD4 prompts opportunistic-infection assessment.
04
Renal, liver, blood count and metabolic profile
Why
Establish maternal safety and monitor ART and pregnancy complications.
Interpretation and limitations
Tenofovir, integrase inhibitors and other agents require regimen-specific review; physiological creatinine and weight changes affect interpretation.
05
Hepatitis and STI screen
Why
Treat coinfections that influence ART, fetal health and delivery care.
Interpretation and limitations
Hepatitis B requires continuous dual-active ART; syphilis and genital infections need prompt pregnancy-appropriate treatment.
06
Ultrasound and fetal monitoring
Why
Provide standard obstetric surveillance plus targeted assessment after late diagnosis, illness or medication concern.
Interpretation and limitations
HIV alone does not mandate invasive fetal testing; avoid fetal scalp electrodes and other blood-exposing procedures when viraemia is detectable.
07
Infant HIV nucleic-acid testing
Why
Detect perinatal infection before antibody tests become interpretable.
Interpretation and limitations
Follow the paediatric schedule from birth through the post-exposure period; maternal antibodies can persist to 18 months.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

False-reactive antenatal screen

An antenatal screening assay can react nonspecifically, so the full confirmatory algorithm must distinguish a false-reactive result from established or acute HIV.

Acute non-HIV viral illness

EBV, CMV, rubella and other infections cause fever, rash and lymphadenopathy but require parallel pregnancy assessment.

Medication-related liver injury

ART toxicity, viral hepatitis, pre-eclampsia and pregnancy-specific liver disease can all raise transaminases; blood pressure, symptoms, virology and drug timing distinguish them.

Obstetric growth disorder

Fetal growth restriction or threatened preterm birth may reflect placental, hypertensive, infectious or social factors beyond HIV and needs standard obstetric assessment.

Infant maternal antibody

Reactive infant antibody testing before 18 months can reflect transferred maternal IgG rather than infant infection.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01DIAGNOSEStart maternal suppression rapidlyFirst stepHIV is newly confirmed or acute infection is suspected during pregnancy.

1Contact the specialist HIV maternity team the same day and obtain viral load, CD4, resistance, hepatitis, renal and liver specimens.
2Start a complete potent ART regimen promptly after interaction and gestation review rather than waiting for every result.
3Assess opportunistic infection, mental health, partner safety, conception context and support needs privately.
4Repeat viral load early to demonstrate decline and modify the regimen if genotype, toxicity or absorption makes it unreliable.

02SUPPRESSMaintain undetectable viral loadPregnancy continues while taking prescribed antiretroviral treatment.

1Reconcile ART at every maternity contact and check supplements, antacids, vomiting and prescription supply.
2Measure viral load at national guideline intervals and around 36 weeks for the delivery decision.
3Continue two HBV-active agents in hepatitis B and manage renal, liver, metabolic and blood-count effects.
4Plan delivery, neonatal medication, infant testing and feeding jointly before labour and record the plan where it is immediately accessible.

03DELIVERChoose birth from viral loadLate-pregnancy viral load and obstetric status are available or labour begins unexpectedly.

1Support planned vaginal birth when viral load is below 50 copies/mL and obstetric assessment is favourable.
2For 50 to 399 copies/mL, individualise vaginal versus planned caesarean birth using trajectory, adherence, duration of suppression and obstetric factors.
3For 400 copies/mL or higher, recommend planned caesarean birth from 39 weeks and use intrapartum intravenous zidovudine when the specialist protocol indicates.
4In unplanned labour, contact the HIV maternity team immediately and minimise fetal blood exposure while acting on the latest reliable viral result.

04NEWBORNComplete neonatal preventionAn infant is born to a person living with HIV.

1Give the risk-stratified neonatal antiretroviral regimen as soon as possible, ideally within four hours.
2Use zidovudine monotherapy for the defined low-risk pathway and a three-drug regimen for high-risk exposure under paediatric dosing.
3Perform HIV nucleic-acid tests at the scheduled birth and follow-up points and complete antibody confirmation after maternal antibody wanes.
4Agree formula feeding or the supported breastfeeding pathway before discharge and maintain maternal and infant follow-up without gaps.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Protects maternal health and suppresses viral load to prevent in-utero and intrapartum transmission.

Pregnancy antiretroviral regimen

Use the exact specialist-selected complete integrase-inhibitor-based or other recommended regimen daily, adjusted for resistance, hepatitis B, gestation, kidney function and interactions.

Do not interrupt around delivery; review folate, cations, antiemetics, rifamycins and anticonvulsants and make changes only with HIV maternity specialists.

Adds intrapartum antiretroviral exposure when maternal suppression is inadequate or transmission risk is otherwise high.

Intravenous zidovudine during labour

Give 2 mg/kg intravenously over one hour, then 1 mg/kg/hour until delivery when the specialist high-viraemia or intrapartum protocol indicates.

Not required routinely with sustained suppression; monitor maternal blood count and infusion, and never let preparation delay urgent obstetric care.

Provides post-exposure prophylaxis to an infant with minimal residual transmission risk.

Low-risk neonatal zidovudine

Start weight- and gestation-adjusted oral zidovudine within four hours of birth for two weeks when all current low-risk criteria are met.

Paediatric HIV specialists confirm risk, dose, formulation and duration; monitor blood count and do not downgrade risk from one isolated maternal result.

Provides intensified presumptive therapy after significant late-pregnancy viraemia, acute acquisition or uncertain maternal treatment.

High-risk neonatal combination prophylaxis

Start the exact paediatric three-drug regimen within four hours of birth, with gestation- and weight-adjusted doses and specialist-defined duration.

Requires paediatric HIV prescribing, renal, liver and marrow monitoring and rapid adjustment if infant testing confirms infection.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Vertical HIV transmission

Uncontrolled maternal virus can establish lifelong infant HIV during pregnancy, birth or breastfeeding when effective maternal, intrapartum and neonatal prevention is absent.

Maternal virological failure

Poor absorption, drug interaction, resistance or interrupted supply can produce viral rebound, restoring maternal disease risk and the possibility of vertical transmission.

Preterm or obstetric morbidity

HIV, coinfection and some treatment or social factors interact with baseline pregnancy risks and require integrated care.

Neonatal drug toxicity

Neonatal antiretroviral prophylaxis can cause anaemia, neutropenia or organ toxicity, which the planned paediatric blood-count and biochemical schedule detects.

Postnatal transmission

Detectable maternal viraemia, mastitis or breast inflammation during breastfeeding can expose an infant who remained HIV-negative through pregnancy and birth.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Measure maternal viral load repeatedly after diagnosis or ART change and near 36 weeks, with urgent repeats for rebound.
Review adherence, supply, vomiting, cation timing, interactions and resistance non-judgmentally at every detectable result.
Monitor maternal renal, liver, haematological, metabolic and obstetric safety according to regimen and pregnancy.
Document mode and timing of birth, intrapartum zidovudine decision and avoidance of unnecessary invasive fetal monitoring.
Confirm neonatal prophylaxis began within four hours and every dose and duration follows gestation and risk.
Complete infant virological and final antibody testing through paediatric HIV follow-up.
During supported breastfeeding check maternal viral load and infant HIV testing at least monthly and stop immediately when safety criteria fail.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Maternal treatment is lifelong

ART is not a temporary pregnancy intervention; continuous suppression protects long-term health and future transmission.

Thirty-six-week load directs birth

A late result translates treatment success into a practical vaginal, individualized or planned-caesarean pathway.

Supplements can undermine suppression

Iron, calcium and magnesium may chelate integrase inhibitors unless food and timing instructions are followed.

Low-risk neonatal care has criteria

Short zidovudine monotherapy applies only when maternal suppression, adherence, acquisition timing and clinical history all support minimal risk.

Maternal antibody complicates infant testing

Virological assays diagnose early infection, while final antibody testing waits until transferred maternal antibody has waned.

Feeding care avoids coercion

Formula eliminates breast-milk transmission; a person choosing breastfeeding needs sustained suppression and an intensive supported monitoring pathway.

11Common pitfallsFrequent interpretation and management errors.

01
Do not delay ART in a newly diagnosed pregnant patient while waiting for every baseline result.
02
Do not switch a suppressive tolerated regimen solely because pregnancy is discovered without specialist review.
03
Do not use one early pregnancy viral load to plan delivery months later.
04
Do not omit intrapartum and neonatal plans from the accessible maternity record.
05
Do not delay infant prophylaxis beyond the first hours while administrative details are clarified.
06
Do not support breastfeeding without sustained suppression, exclusive-feeding advice and monthly maternal and infant monitoring.