EVIDENCE is emerging that AIDS drugs can cause serious birth defects in a
minority of babies born to HIV-positive mothers.
Most specialists stress that, on balance, they would still urge pregnant
women with HIV to take drugs to minimise the chance of their babies being
infected by the virus. But they say that larger studies are now needed to
quantify the risks associated with taking AIDS drugs during pregnancy.
The concerns stem from a study led by St茅phane Blanche of the Necker
Hospital in Paris. He has examined the cases of around a thousand pregnant women
with HIV and found that eight gave birth to babies who, though HIV-negative,
suffered from a neurodegenerative condition that kills its victims in infancy.
鈥淎ll obstetricians and gynaecologists in France have been informed about our
findings,鈥� says Blanche, who is now preparing a paper for publication.
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The condition highlighted by Blanche is thought to be caused by abnormalities
in mitochondria, the energy 鈥渇actories鈥� within our cells. The babies鈥� mothers
had all taken a combination of the drugs AZT and 3TC from week 32 of their
pregnancy.
鈥淭his condition is an extraordinarily rare mitochondrial disorder that you
might expect to see in only 1 in 10 000 or 1 in 100 000 births,鈥� says Gareth
Tudor-Williams, a paediatric AIDS specialist at Imperial College School of
Medicine in London. 鈥淚f a link is confirmed we will need to do a very careful
search of the data worldwide.鈥�
Concerns are being fuelled by a second study from a team led by Ofelina
Olivero of the National Cancer Institute near Washington DC. In the journal
AIDS (vol 13, p 919), the researchers report that AZT is incorporated into
the DNA of white blood cells in people treated with the drug鈥攊ncluding
pregnant women and their babies. This is because AZT mimics thymidine, one of
the four nucleosides that make up the genetic code. Olivero and her colleagues
warn that the changes may increase the chance of developing cancer.
Experts say that neither study changes their advice to pregnant women who are
HIV-positive: they should still take drugs to protect their unborn babies from
infection. Indeed, as 快猫短视频 went to press, medical authorities
in France and the US were preparing statements on Blanche鈥檚 findings which are
expected to stress the benefits of using the drugs.
Without medical intervention, a pregnant woman with HIV has a 25 to 35 per
cent chance of infecting her baby. Taking AZT in the third trimester can slash
the risk of infection to less than 10 per cent. Choosing to have a Caesarean
delivery and avoiding breast-feeding can reduce infection rates still
further鈥攚ith some studies suggesting it is possible to cut perinatal
transmission of HIV to 2 per cent or less.
Some Western countries, notably France and the US, have already achieved big
reductions in the number of babies infected with the virus
(see Figure).
But specialists are worried that the advent of potent drug cocktails means
many women carrying HIV and taking large doses of drugs now feel well enough to
get pregnant. 鈥淚t really would be unwise for women to get pregnant while on
these drugs,鈥� says Tudor-Williams. 鈥淏ut we鈥檙e observing cases already.鈥�