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[afro-nets] Placental microtransfusions and HIV/AIDS

Placental microtransfusions lead to transmission of AIDS virus
during childbirth, study
22 November 2005
University of North Carolina at Chapel Hill

Transmission of HIV, the virus that causes AIDS, from pregnant
women to their infants sometime during childbirth is a huge in-
ternational problem, studies have shown. Between 25 percent and
35 percent of babies born to untreated HIV-infected mothers be-
come infected themselves.

That's a half million newborn worldwide every year facing
chronic illness and premature death on their first day out of
the safety of the womb.

"The question has always been how does the virus get from the
mothers to the babies?" said principal investigator Dr. Steven
Meshnick, professor of epidemiology at the University of North
Carolina at Chapel Hill School of Public Health. "We have known
very little about it."

Now, Meshnick and colleagues think they have discovered a major
reason why that occurs. A new study they conducted with 149
pregnant HIV-infected women in the African nation of Malawi
showed that tiny amounts of virus-laden blood leak from women's
placentas to babies during labor. All of the subjects and their
babies had been given single-dose anti-retroviral drugs to mini-
mize HIV transmission.

"This work shows strongly for the first time that what we call
placental microtransfusions during birth are responsible for a
large part of the transmission of HIV from mother to baby," the
scientist said. "To our knowledge, there have never been any
data like this before."

A report on the research appears today (Nov. 21) in the latest
issue of the journal PloS Medicine. PloS is an acronym for Pub-
lic Library of Science.

Besides Meshnick, UNC epidemiology authors are Dr. Jesse Kwiek,
a postdoctoral fellow; graduate student Alisa Alker; and assis-
tant professor Dr. William Miller, also assistant professor of
medicine at the UNC School of Medicine. Other authors are Drs.
Victor Mwapasa, Eyob Tadesse and Malcolm Molyneux of the Univer-
sity of Malawi, Dr. Danny A. Milner, a Harvard University pa-
thologist, and Dr. Stephen Rogerson, associate professor of
medicine at the University of Melbourne.

The study involved measuring -- in umbilical cord blood samples
-- a protein known as placental alkaline phosphatase as an indi-
cator of maternal-fetal microtransfusion.

"This enzyme, made in the placenta, is very big -- usually too
big to pass through the natural barrier that protects babies
from disease-causing organisms mothers sometimes carry before
birth," Meshnick said. "We figured that if we found it in blood
from the umbilical cord, which links the placenta to the baby,
that would be an indication of mixing, that something tore in
the placenta and leaked the mothers' virus-contaminated blood to
the infant."

Researchers then compared what they found in cord blood to
whether or not infants were infected with HIV, he said.

"We looked for a statistical relationship between the presence
of the enzyme and the risk of infection in the babies," Meshnick
said. "We found a very strong correlation between the enzyme and
the risk of infection."

It appears that transmission of the virus occurs during labor --
when contractions occur -- rather than during passage of the
baby through the birth canal, he said.

"It has been known for a long time that HIV-infected women who
undergo caesarean section before they go into labor do not
transmit the virus, whereas those who undergo emergency C-
sections after they go into labor do transmit it," Meshnick
said. "What we saw was consistent with this. It looks like di-
rect mother-to-child blood mixing occurring during labor leads
to infection."

The new findings indicate that intervening just before birth by
such suggested methods as sanitizing the birth canal may not
work, he said. A better alternative might be to have pregnant
women start taking anti-retrovirals before going into labor.

Support for the study came from the UNC Center for AIDS Research
and the National Institute of Allergy and Infectious Disease.
Dr. Myron Cohen, professor of medicine and chief of infectious
diseases at the UNC School of Medicine, directs the center.

David Williamson
University of North Carolina at Chapel Hill
Tel: +1-919-962-8596

Leela McCullough, Ed.D.
Director of Information Services
30 California Street, Watertown, MA 02472, USA
Tel: +1-617-926-9400
Fax: +1-617-926-1212

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