Factors affecting HIV transmission from mother to child

factors affecting mother-to-child transmission of HIV-1

Transmission from mother-to-child of HIV is affected by a number of factors which can be divided into:

• viral
  • viral load - transmission is increased in the presence of high levels of maternal viraemia
  • viral genotype and phenotype
  • viral resistance
    
    
• maternal
  • maternal immunological status
    • transmission is more likely with decreased maternal immune status, reflected by low CD4+ counts, low CD4+ percentages or high CD4+/CD8 ratios
  • maternal nutritional status
    • serum vitamin A levels in HIV-1 positive mothers have been correlated with the risk of transmission. The mean vitamin A level in those mothers who transmitted virus to their children was significantly lower than in those who did not transmit
  • maternal clinical status
  • behavioural factors
    • cigarette smoking, maternal hard drug use, unprotected sexual intercourse during pregnancy have been associated with an increased rate of transmission from mother to child
  • antiretroviral treatment
    
    
• obstetrical
  • prolonged rupture of membranes (> 4 hours)
  • mode of delivery - delivery by caesarean section has been shown to be protective in some prospective follow-up studies
  • intrapartum haemorrhage
  • obstetrical procedures
  • invasive fetal monitoring
    
    
• fetal
  • prematurity
  • genetic
  • multiple pregnancy
    
    
• infant
  • breastfeeding
    • is responsible for a high proportion of mother-to-child transmission in developing countries
  • gastrointestinal tract factors
    • decreased acidity, decreased mucus, lower IgA activity and thinned mucosa in the newborn gastro-intestinal tract, may facilitate transmission following ingestion of virus in utero or at birth
  • immature immune system
    • newborn immune system may also be deficient in macrophage and T cell immune response, increasing the susceptibility to infection (1).

Reference:

• (1) World Health Organization (WHO) and United Nations Programme on HIV/AIDS (UNAIDS) 1998. HIV in pregnancy: A review