NEW YORK, April 30 (Reuters) -- Smoking during pregnancy increases the chance that a woman infected with HIV will pass the virus onto her unborn child, new research shows.
Among HIV-infected women who smoked and did not take prescribed drugs like AZT, about one-third gave birth to HIV-infected babies. In comparison, 22% of HIV-positive mothers who did not smoke had seropositive babies.
The adverse effects of smoking on the placenta are thought to lead to the increased risk. "In addition to contributing to poor health outcomes, we know that nicotine is toxic to blood vessels and adversely affects the placenta, promoting premature rupture of the membranes surrounding the baby," explains Dr. Barbara Turner, professor of medicine at Jefferson Medical College in Philadelphia, Pennsylvania.
"Our study shows that smoking may be especially dangerous for HIV-positive pregnant women because its effects may increase the baby's exposure to blood and other maternal secretions that contain the virus during delivery," the lead study researcher adds. "For women who are not treated with antiretroviral medications and who have more advanced disease, smoking is associated with a greatly increased risk of maternal-child HIV transmission."
Turner and colleagues studied statewide Medicaid claims data from New York State, where 60% to 80% of HIV-infected women are on welfare. It is also the state with the largest number of women and children with AIDS. The researchers looked at the records of 901 of these women and their children who were born between 1988 and 1990.
"We were able to determine mom's HIV status by examining multiple pieces of evidence including diagnosis of HIV infection or AIDS, HIV/AIDS complications and diagnosis, or a record of AZT treatment," Turner says. "Similar criteria were used to determine the HIV status of children, but we looked for somewhat different HIV/AIDS complications that are characteristic of children, and our criteria also differed by the child's age."
Turner and her team also used vital statistics records to gather additional information on factors such as the mother's age, race, smoking history, and use of illicit drugs and alcohol.
Even after adjusting for these factors, smoking continued to be strongly associated with an increased rate of mother-fetus HIV transmission. This was especially true for women with more advanced AIDS.
The researchers note that AZT (zidovudine) and other antiviral drugs were not widely used during the study years. Currently, pregnant women who are HIV-infected are offered such drugs, which can reduce their viral load and the risk of transmission from about 1 out of 4 to about 1 out of 10.
"If a pregnant, HIV-positive woman takes AZT or another antiretroviral drug, which reduces the mother's viral load, the effects of smoking on (HIV) transmission may disappear," Turner points out. "But smoking is still associated with low birth weight babies and poor birth outcomes for this very vulnerable population."
Turner says she believes this study underscores the need for health care providers to emphasize smoking cessation to all pregnant women, but especially those who are HIV-positive.
"Smoking is a difficult habit to beat, but it can be done," she says. "If health care providers use a number of different modalities to promote smoking cessation and do vigorous follow-up of HIV-infected women, they can improve birth outcomes and may ultimately spare more children from contracting HIV."
SOURCE: Journal of Acquired Immune Deficiency Syndrome and Retrovirology (1997;14(4):327-337)
