factors affecting HIV transmission from mother to child

Last edited 03/2018

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).

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