Risk Factors For Mother-To-Child HIV Transmission (MTCT)
From SA Dept of Health document "Prevention of Mother-to-Child HIV Transmission and Management of HIV Positive Pregnant Women" launched October 2000.
4.1 Maternal Factors
a. Immune status:
The risk for MTCT is increased with the severity of immune deficiency. Women with low CD4 counts (<200 cells/ml or less) are more likely to transmit HIV to their infants.
b. Vitamin A deficiency:
Studies on MTCT have suggested an association between Vitamin A deficiency in the mother and risk of MTCT. Vitamin A deficiency in HIV- infected mothers is associated with a higher risk of HIV transmission from mother to child. Ongoing trials in Malawi, South Africa, Tanzania and Zimbabwe are currently studying whether adding vitamin supplements to pregnant women’s diet will affect the risk of MCTC.
4.2 Behavioural factors
Cigarette smoking, drug use, and unprotected sexual intercourse during pregnancy has been associated with an increased risk of MTCT.
4.3 Obstetrical Factors
a. Placental infection:
Infection of the chorion or the amnion may increase the chance of MTCT. Genital infections and especially sexually transmitted diseases (STD’s) may result in chorioamnionitis. Prolonged rupture of membranes during labour is another common cause of infection.
There is a relatively high risk of transmission during delivery due to presence of the virus in blood and mucus in the birth canal. Therefore, various methods of vaginal washing (lavage) before and during delivery are being investigated in several developing countries. In a trial performed in Malawi, lavage-using chlorhexidine showed no overall difference in rates of MTCT, but did show a significant reduction in cases where membranes were ruptured for more than four hours. It also resulted in significant reduction of infant mortality and morbidity.
b. Mode of delivery:
The mode of delivery may also influence the risk of MTCT. Elective Caesarean section births has been shown to reduce the risk of MTCT.
4.4 Infant Factors
a. Breastfeeding:
HIV is transmissible through breastmilk. Subsequently breastfeeding is associated with at least one-third all MTCT.
b. Foetal trauma:
Traumatic births and births where the foetal skin is traumatised from obstetrical procedures increase the risk of MTCT.
c. Prematurity:
Pre term births tend to place the infant at higher risk for MTCT as compared to full term births.
4.5 Viral Factors
a. HIV Viral load:
A high level of circulating HIV virus (viral load) is an important contributor to MTCT. The higher the viral load the more likelihood that MTCT will occur. There is a higher risk of MTCT in women with advanced HIV disease (AIDS) or documented high viral loads (e.g. >50,000 HIV viral particles or more/ml).
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