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Pregnancy and HIV Transmission

June 1999

In recent years, advances in decreasing the rate of mother-to-child HIV transmission (vertical transmission) have occurred. New information and anti-HIV treatments have made it more likely that women will give birth to healthy, HIV-negative babies. With good prenatal and HIV care and the use of anti-HIV therapies for pregnant women and their newborns, vertical transmission rates have decreased to 8 percent and sometimes reach even lower. Until recently, anti-HIV treatments to reduce the risk of mother-to-child HIV transmission involved a three-part AZT (zidovudine, Retrovir®) treatment regimen. First, the drug is given at the 14th week of pregnancy and throughout the rest of the pregnancy. Then, the mother receives AZT intravenously (injection in a vein) during labor. Finally, the newborn child receives a liquid formulation of AZT for six weeks after birth.

While this remains the standard regimen for preventing vertical transmission in the U.S. and Western Europe, it's only standard because it represents the method used in the first and only major study conducted on the subject, not because it has proven superior to other approaches. Other regimens are finally being explored, including shortened courses of AZT, a shortened course of AZT + 3TC (lamivudine, Epivir®), as well as nevirapine (Viramune®) given alone, and more potent combinations that include protease inhibitors. Some of these new regimens are likely to prove just as, if not more, effective in preventing transmission than AZT alone. However, the effect of these regimens on how well the fetus develops also remains unknown.

In addition to the use of anti-HIV drugs, other factors affect the risk of vertical transmission. Four factors have shown particular importance. These include: the mother's viral load; the mother's adherence to her anti-HIV therapy; the baby's age at birth (premature babies are more likely to be HIV-infected); and the length of time blood and other fluids containing HIV were present during delivery. Other factors include the mother's overall general health, access to care during pregnancy (prenatal care) and breast feeding. (Note: HIV can be transmitted through breast milk. Women with HIV are discouraged from breast feeding their children.)

Elective cesarean section might also reduce the risk of transmission. Some researchers believe that a planned c-section before the woman's membranes rupture and labor begins will cut down the amount of fluid the infant is exposed to, thereby reducing the risk of transmission. However, response to a recent scientific report supporting elective c-section has been mixed, primarily because it remains unclear whether the benefits of this surgery outweigh the known risks to the mother.

There are still many unknowns regarding the best way to reduce the risk of vertical transmission. Even if a guideline is someday proposed, not every woman will choose to follow it, nor should she be expected to. In the end, the most important step in preventing vertical transmission remains taking good care of the pregnant woman.

In addition to providing pregnant women with the best possible HIV care, (the Federal Guidelines recommend she be treated as any other adult, regardless of her pregnancy status), she should also receive good prenatal care, preferably administered by providers educated about HIV and pregnancy. She should be given the best and most up-to-date information regarding HIV and pregnancy and supported in her decision to proceed with her own pregnancy.

It may not yet be possible to offer women an iron-clad guarantee that they will deliver healthy, HIV-negative babies. However, with access to good prenatal care, use of available anti-HIV treatment, and avoidance of breast feeding, the chances are very good that vertical transmission will successfully be prevented.

For information on preventing mother-to-child HIV transmission, call the National HIV/AIDS Treatment Hotline and request the Mother-to-Child HIV Transmission Prevention Discussion Paper (or simply print out).

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