Risk Factors For Transmission Of Hiv1

Rates of transmission of HIV-1 from mother to child are presently less than 2% in most major HIV-1 centers throughout the United States. Prior to the use of zidovudine (ZDV) chemoprophylaxis for reduction of perinatal transmission, perinatal transmission rates ranged between 15 and 39%. In the adult female population, risk factors for

Table 1

Factors Affecting Vertical Transmission of HIV-1

Maternal factors Viral load

CD4 lymphocyte count Maternal stage of disease Primary HIV infection during pregnancy Sexually transmitted diseases Obstetrical factors

Prolonged rupture of membranes Invasive procedures Placenta previa Chorioamnionitis Mode of delivery Infant factors Prematurity Birth order of twins Postnatal factors important to transmission Breast-feeding acquiring HIV-1 include intravenous drug abuse, unprotected sexual intercourse, needle-stick injuries, and significant exposure to HIV-1-infected blood. Factors that are associated with transmission of HIV-1 from mother to infant are listed in Table 1.

Maternal risk factors associated with perinatal transmission of HIV-1 infection include an elevated maternal HIV-1 RNA viral load, severe immune suppression, AIDS-defining illness, and lack of use of ZDV during pregnancy (29,30,34-36). Several obstetrical practices, such as amniocentesis or use of a scalp electrode, may expose the infant to HIV-1-infected blood (37,38). The presence of chorioamnionitis (39) and prolonged rupture of membranes (26,38) are also associated with a higher risk of transmission.

Infant factors include prematurity (<37 weeks of gestation) (40) and birth order of twins, with twin A more likely to be infected (41). In developing countries, additional risk factors include anemia, malnutrition, and vitamin A deficiency (42). Postnatally, HIV-1 can be transmitted by ingestion of human milk from HIV-1-infected women (32,33). HIV-1 has been identified in breast milk (43,44). In a meta-analysis of several published studies, the estimated risk of transmission of HIV-1 through breast milk was 29% (95% confidence interval [CI] 16-42%) in women who acquired HIV-1 postnatally and 14% (95% CI 7-22%) in women who were chronically infected with HIV-1 (45). In the United States and developed countries, where safe, affordable, and accessible alternative feeding methods are available, it is recommended that HIV-1-infected women avoid breast-feeding (46).

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