An estimated one-third of HIV-positive women who smoke during pregnancy
and do not take zidovudine (AZT [Retrovir]) may pass HIV on to their babies.
Researchers at Thomas Jefferson University, Philadelphia, and the New
York State Department of Health have found an association between cigarette
smoking and an increase in maternal-child HIV transmission. An analysis
of 901 HIV-infected women on Medicaid and their babies delivered between
1988 and 1990 in New York, the state with the largest number of women and
children with AIDS in the United States, showed that an estimated one-third
of these women who smoked and did not take antiretroviral drugs like AZT
passed HIV on to their children. Study results appeared in the April issue
of 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 that
nicotine 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 of
medicine at Thomas Jefferson University Hospital. "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. For women who
are not treated with antiretroviral medication and who have more advanced
disease, smoking is associated with a greatly increased risk of maternal-child
Researchers studied statewide Medicaid claims data from New York, which
provided them with a large study sample since 60% to 80% of HIV-infected
women in the state are on Medicaid. Researchers developed methods to match
each woman to her child and then establish the HIV status of both mother
and baby. The entire study was conducted without the Jefferson researchers
having any information that could be linked to a specific patient, to ensure
"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 like Pneumocystis pneumonia, a combination of complications
and diagnoses or a record of AZT treatment," said Dr. Turner. "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."
Researchers also used vital statistics records to gather additional
information on factors like the mother's age, race, smoking history, and
use of illicit drugs and alcohol. Despite adjusting for these factors,
smoking continued to have a strong association with an increased rate of
maternal-fetal HIV transmission. This was especially true for women with
Zidovudine and other antiretroviral drugs were not widely used during
the study years. Currently, pregnant women who are HIV-infected are being
offered such drugs, which can reduce their viral load and the risk of transmission
from approximately 1 out of 4 to approximately 1 out of 10.
"If a pregnant, HIV-positive woman takes AZT, or another antiretroviral
drug, which reduces the mother's viral load, the effect of smoking on transmission
may disappear, but smoking is still associated with low birth weight babies
and poor birth outcomes for this very vulnerable population," said
Emphasize Smoking Cessation for HIV-Positive Pregnant Women
Dr. Turner believes that 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 said. "If health-care providers use a number of different modalities
to promote smoking cessation and employ vigorous follow-up of HIV-infected
women, they can improve birth outcomes and may ultimately spare more children
from contracting HIV."