HIV infection in young children most commonly arises as a result of mother-to-child transmission (MTCT). It is thought that only 1.5-2% of MTCT occurs transplacentally during pregnancy. The vast majority occurs due to maternofetal transmission of blood during parturition or postnatal breast-feeding.
All pregnant women are recommended screening for HIV infection, syphilis, hepatitis B and rubella in every pregnancy at their booking antenatal visit. If a woman declines an HIV test, this should be documented in the maternity notes, her reasons should be sensitively explored and screening offered again at around 28 weeks.
A negative maternal HIV test at booking does not preclude neonatal infection - maternal infection and seroconversion can occur at any time during pregnancy and lactation. This is well-documented in countries with a high prevalence of HIV and has been seen in the UK.
- In 2013, 2.5 pregnant women per 1,000 (1,750/688,760) were HIV-positive and the majority (five in six) had been diagnosed prior to pregnancy.
- The prevalence of UK-born women living with HIV has increased from approximately 17,000 in 2006 to 26,000 in 2013.
- Without intervention, between 15-45% of babies born to HIV-infected mothers in the most severely affected countries are also infected.With appropriate interventions transmission rates can be reduced to less than 1%.
Risk of MTCT
This is increased with:
- Higher levels of maternal viraemia.
- HIV core antigens.
- Lower maternal CD4 count.
- Primary HIV infection occurring during pregnancy.
- Co-existing other sexually transmitted disease .
- Possibly malaria.
- Invasive intrapartum procedures - eg, fetal scalp electrodes, forceps, ventouse.
- Rupture of membranes (especially if delivery is more than four hours after the membranes ruptured).
- Vaginal delivery.
- Preterm birth.
- Female babies more likely to be infected early (transplacental/perinatal routes).
- Advanced maternal age.
- The firstborn of twins (born to an HIV-infected mother).
Factors that decrease risk of transmission are:
- Higher levels of neutralising HIV antibody.
- Elective caesarean section.
- Zidovudine (ZDV).
- Less invasive monitoring and intrapartum procedures.
Mother-to-child transmission (MTCT) of HIV infection can be greatly reduced through early diagnosis of maternal HIV infection.
- Pregnant women should be offered screening for HIV early in pregnancy because appropriate antenatal interventions can reduce MTCT of HIV infection.
- Interventions to reduce MTCT of HIV during the antenatal period include antiretroviral therapy (ART), elective caesarean section delivery and avoidance of breast-feeding after delivery.
- These interventions can reduce the risk of mother-to-child HIV transmission from 25-30% to less than 1%.
- All pregnant women who are HIV-positive should be screened and appropriately treated for genital infections during pregnancy. This should be done as early as possible in pregnancy and repeated at about 28 weeks.
- Presentation with symptoms or signs of pre-eclampsia, cholestasis or other signs of liver dysfunction during pregnancy may indicate drug toxicity and early liaison with HIV physicians is essential.
Women who require HIV treatment for their own health should take ART and continue treatment postpartum. They may also require prophylaxis against pneumocystic pneumonia (PCP), depending on their CD4 lymphocyte count.
HIV resistance testing should be performed prior to initiation of treatment unless the woman presents late. A further resistance test is recommended after short-course treatments to ensure that mutations are not missed with reversion during the off-treatment period.
Women already taking ART and/or PCP prophylaxis before pregnancy should not discontinue their medication.
- ART is given to prevent MTCT and to prevent maternal disease progression. The optimal regimen is determined on a case-by-case basis according to prevailing guidelines.
- Zidovudine (ZDV) is indicated for use in pregnancy for prevention of MTCT of HIV but single-agent ZDV therapy which does not suppress plasma viraemia to undetectable levels may allow the emergence of resistant virus.
- Potent combinations of three or more antiretroviral drugs have now become the standard of care. (Combined ART is sometimes given the acronym cART). Women with advanced HIV should be treated with an ART regimen. The start of treatment should be deferred until after the first trimester, if possible, and should be continued after delivery.
- For women who do not require HIV treatment for their own health, ART should be initiated by the 24th week of pregnancy and discontinued at delivery. If they have a plasma viral load of less than 10,000 copies/ml and are prepared to be delivered by elective caesarean section, an acceptable alternative is ZDV monotherapy initiated between 20 and 28 weeks, given orally, 250 mg twice daily and intravenously started four hours before beginning the caesarean section, continuing until the umbilical cord has been clamped. ZDV is usually administered orally to the neonate for four to six weeks.
- cART maximises the chance of preventing transmission and represents optimal therapy for the mother but may increase the risk of drug toxicity to the fetus.
- The use of antiretrovirals to reduce MTCT has resulted in resistant mutations. Various strategies have been proposed to minimise this, including giving all HIV pregnant women ART for life, giving short courses of drugs and ceasing treatment after cessation of breast-feeding.
A decision about mode of delivery should be made by 36 weeks of gestation. The proportion of HIV-diagnosed women who took some form of ART prior to delivery rose to 98% in 2010. This was reflected in an increase in vaginal deliveries and a drop in pre-labour (elective) caesarian sections.
- A planned vaginal delivery can be offered to women taking ART who have a plasma viral load of less than 50 copies/ml. Women who opt for a planned vaginal delivery should have their membranes left intact for as long as possible. Use of fetal scalp electrodes and fetal blood sampling should be avoided.
- Women with HIV and hepatitis C virus co-infection can have a vaginal delivery providing they are taking effective ART.
- Delivery by pre-labour caesarean section between 38-39 weeks to prevent labour and/or ruptured membranes is recommended for:
- Women taking ART who have a plasma viral load greater than 50 copies/ml .
- Women taking ZDV monotherapy as an alternative to ART.
- Delivery by pre-labour caesarean section for obstetric indications or maternal request should be delayed until after 39 weeks in women whose plasma viral load is less than 50 copies/ml, to reduce the risk of transient tachypnoea of the newborn.
Studies suggest that for women with a viral load above 50 copies/ml the risk of placental transmission is half that for pre-labour section compared to vaginal delivery. Below that level, there is no difference.
Breast-feeding should be avoided, as it increases MTCT by approximately 15%. However, in developing countries, where caesarean section is unavailable and there is no alternative to breast-feeding, the World health Organization (WHO) recommendations are that HIV-infected pregnant women should be offered ART, the duration of treatment depending on the CD4 count. Infants should receive once-daily nevirapine (NVP) from birth for six weeks.
MTCT of HIV is largely preventable where universal antenatal HIV screening is undertaken, exclusive artificial formula feeding is feasible and where there is the provision for ART and delivery by caesarean section when necessary.
- In the absence of intervention, MTCT transmission was reported to occur in 25% of deliveries and was reduced to 8% with ART with ZDV.
- cART, caesarean section and avoidance of breast-feeding can further reduce the risk of transmission to 1%.
- In the UK, MTCT rates declined from 2.2% in 1998 to 0.46% in 2010.Current data suggest that pregnancy has no effect on accelerating the development of AIDS, HIV-related diseases or severe immunosuppression for up to one year after delivery or abortion.
- HIV infection may adversely affect pregnancy, especially in terms of the overall risk of spontaneous abortion and maternal postpartum endometritis.
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