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Worldwide, it is estimated that 2.5 million children younger
than 15 years are infected with human immunodeficiency virus type
1 (HIV-1), with more than 2.2 million HIV-1-infected children in Africa
alone.1 In 2006, some 330,000 children died from
HIV-1 infection. Many millions have been orphaned as a result of
the HIV-1-related deaths of their parents. In the United States,
rates of new pediatric HIV infections increased from 1982 until
1995. Since 1995, the use of antiretroviral agents to prevent mother-to-child-transmission
of HIV-1 has significantly reduced perinatal transmission. Rates
of new HIV-1 infections in children younger than 15 years in the
United States have declined from a high of 2500 per year in the
early 1990s to approximately 100 to 200 per year.2 The
number of HIV-1-infected infants and children in the United States
is currently estimated to be 10,000.2
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More than 95% of HIV-1-infected infants and children
acquire their infection vertically, during gestation, especially
later gestation, or during labor and delivery. An increasing proportion
of women with HIV-1 contracted their infection through heterosexual
contact, although injection drug use and substance abuse still play
a significant role because injection drug use is prevalent in about
one third of all HIV-1-infected women of childbearing age.2 Ethnic
minorities and individuals with low income are markedly overrepresented
among HIV-1-infected women and HIV-1-infected infants and children
in the United States.2 Child sexual abuse and transfusion
of contaminated blood products result in an exceedingly small number
of HIV infections in children in the United States. Adolescents
participating in adult risk behaviors (sexual activity and injection
drug use) are increasing and represent the largest number of new
pediatric infections.2
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The timing and mechanism of perinatal HIV-1 transmission are not
completely understood. Evidence of HIV-1 in fetal tissue is found
in approximately 30% of first- and early second-trimester abortions
by women who are HIV-1 infected. It appears likely that in the preantiretroviral
era, the majority of infants were infected in the peripartum period,
either through transplacental passage of virus (late pregnancy or
at the time of labor) or by exposure to HIV-1 during birth. Because
antiretroviral therapy has been successful in reducing perinatal
HIV-1 transmission, particularly late in pregnancy and at the time
of delivery, transmission earlier in pregnancy now represents the
more common period of transmission. Postnatal transmission through
breast-feeding is well documented,3 and this fact
underlies the recommendation that mothers with HIV-1 infection should
not breast-feed if safe, alternative infant nutrition is available. Mixed
feeding (combination of breast and formula) carries a higher risk
for transmission than breast-feeding alone.4 In
areas where a safe alternative is not available, breast-feeding
exclusively should be maintained until the infant can obtain adequate nutrition
without breast-feeding.
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Of children born to HIV-1–infected women not receiving
antiretroviral treatment, 13% to 40% will be infected.5 Many
maternal and obstetric factors that contribute to the risk of perinatal
transmission have been identified. Prematurity, ...