Maternal/Fetal AIDS

Maternal-fetal HIV transmission may occur at three stages during the perinatal period: pregnancy, delivery, and nursing. Overall, the rate of perinatal transmission varies from 20%- 60%. Rates of HIV-1 and HIV-2 transmission are similar. Intrauterine transmission probably occurs in 20%-30% of HIV-positive mothers, but this rate can be modified if the mother receives antiviral therapy (e.g. zidovudine). Rates of transmission to the fetus are probably higher if the mother becomes infected during her pregnancy and becomes viremic at that time rather than being infected before she becomes pregnant. Transmission during delivery occurs; the risks are unknown but thought to be high. For comparison, 90% of hepatitis-B transmissions are known to occur during delivery, and therefore delivery is likely to be a significant risk period for HIV transmission as well. The transmission of AIDS postpartum also occurs, since the virus is found in breast milk. A 15% increase in perinatal HIV transmission has been documented in infants breast fed exclusively, as compared with formula-fed infants. The risk of transmission increases with the number of months of breast feeding. However, without breast feeding, many babies in the tropics will likely be malnourished or develop diarrhea due to poor hygiene. While HIV-positive mothers in Europe and America are advised not to breast feed their babies, if babies in the tropics are not breast fed, the increase in infant mortality may exceed mortality from AIDS.

In July 1998 the United Nations changed their policy and recommended that women who were HIV-positive should not breast feed their infants. The UN acknowledged that this is a very controversial policy and would be against well-established social customs in many countries. But in 1997 UNAIDS estimated that 30% of the 600,000 children in the world who became HIV infected, acquired their infection from breast feeding. Recent studies have shown that as many as 70% of the women at prenatal clinics may be HIV-positive, and 30% or more of women in six African countries were infected. The major problem with the new policy is that 90% of women in developing countries do not know whether or not they are infected and worldwide at least 30% of pregnant women receive no antenatal care.

Women who have symptomatic HIV infections or AIDS have a significantly increased rate of miscarriage, low-birth-weight infants, intrauterine fetal death, and preterm delivery; however, asymptomatic HIV-positive infections have not been associated with increased complications of pregnancy, according to the work of Kumar and colleagues. Placental size may be larger in HIV-infected mothers, a nonspecific sign seen in numerous infections.

Although it had been previously believed that a single pregnancy does not adversely affect the course of HIV disease in the mother, a recent controlled study by Kumar and colleagues from India refutes this. HIV-infected pregnant and nonpregnant women were matched for CD4 counts, age, and parity. The mean survival time was about 19 months for the pregnant women and about 23 months for the nonpregnant women. Many of the infants were delivered preterm, with high infant mortality. Multiple pregnancies in the HIV-infected mother are thought to speed progression towards full-blown AIDS. A possible mechanism for this is the activation of latently infected helper cells by the circulating paternal antigens from the fetus, viral production being stimulated by each successive pregnancy.