Researchers Find Association Between Cigarette Smoking and Maternal-Child HIV Transmission

An estimated one-third of HIV-positive women who smoke during pregnancyand do not take zidovudine (AZT [Retrovir]) may pass HIV on to their babies.

Researchers at Thomas Jefferson University, Philadelphia, and the NewYork State Department of Health have found an association between cigarettesmoking and an increase in maternal-child HIV transmission. An analysisof 901 HIV-infected women on Medicaid and their babies delivered between1988 and 1990 in New York, the state with the largest number of women andchildren with AIDS in the United States, showed that an estimated one-thirdof these women who smoked and did not take antiretroviral drugs like AZTpassed HIV on to their children. Study results appeared in the April issueof the Journal of Acquired Immune Deficiency Syndromes and Human Retrovirology.

Smoking Increases HIV Transmission Particularly in Absence of AZT

"In addition to contributing to poor birth outcomes, we know thatnicotine is toxic to blood vessels and adversely affects the placenta,promoting premature rupture of the membranes surrounding the baby,"explained Barbara J. Turner, MD, principal investigator and professor ofmedicine at Thomas Jefferson University Hospital. "Our study showsthat smoking may be especially dangerous for HIV-positive pregnant women,because its effects may increase the baby's exposure to blood and othermaternal secretions that contain the virus during delivery. For women whoare not treated with antiretroviral medication and who have more advanceddisease, smoking is associated with a greatly increased risk of maternal-childHIV transmission."

Researchers studied statewide Medicaid claims data from New York, whichprovided them with a large study sample since 60% to 80% of HIV-infectedwomen in the state are on Medicaid. Researchers developed methods to matcheach woman to her child and then establish the HIV status of both motherand baby. The entire study was conducted without the Jefferson researchershaving any information that could be linked to a specific patient, to ensurepatient confidentiality.

"We were able to determine mom's HIV status by examining multiplepieces of evidence including diagnosis of HIV infection or AIDS, HIV/AIDScomplications like Pneumocystis pneumonia, a combination of complicationsand diagnoses or a record of AZT treatment," said Dr. Turner. "Similarcriteria were used to determine the HIV status of children, but we lookedfor somewhat different HIV/AIDS complications that are characteristic ofchildren and our criteria also differed by the child's age."

Researchers also used vital statistics records to gather additionalinformation on factors like the mother's age, race, smoking history, anduse of illicit drugs and alcohol. Despite adjusting for these factors,smoking continued to have a strong association with an increased rate ofmaternal-fetal HIV transmission. This was especially true for women withlater-stage AIDS.

Zidovudine and other antiretroviral drugs were not widely used duringthe study years. Currently, pregnant women who are HIV-infected are beingoffered such drugs, which can reduce their viral load and the risk of transmissionfrom approximately 1 out of 4 to approximately 1 out of 10.

"If a pregnant, HIV-positive woman takes AZT, or another antiretroviraldrug, which reduces the mother's viral load, the effect of smoking on transmissionmay disappear, but smoking is still associated with low birth weight babiesand poor birth outcomes for this very vulnerable population," saidDr. Turner.

Emphasize Smoking Cessation for HIV-Positive Pregnant Women

Dr. Turner believes that this study underscores the need for health-careproviders to emphasize smoking cessation to all pregnant women, but especiallythose who are HIV-positive.

"Smoking is a difficult habit to beat, but it can be done,"she said. "If health-care providers use a number of different modalitiesto promote smoking cessation and employ vigorous follow-up of HIV-infectedwomen, they can improve birth outcomes and may ultimately spare more childrenfrom contracting HIV."