Babies at risk

 作者:须戤     |      日期:2019-03-08 05:10:02
By Michael Day 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 Stéphane 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. “All obstetricians and gynaecologists in France have been informed about our findings,” says Blanche, who is now preparing a paper for publication. The condition highlighted by Blanche is thought to be caused by abnormalities in mitochondria, the energy “factories” within our cells. The babies’ mothers had all taken a combination of the drugs AZT and 3TC from week 32 of their pregnancy. “This 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,” says Gareth Tudor-Williams, a paediatric AIDS specialist at Imperial College School of Medicine in London. “If a link is confirmed we will need to do a very careful search of the data worldwide.” 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—including 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 New Scientist went to press, medical authorities in France and the US were preparing statements on Blanche’s 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—with 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. “It really would be unwise for women to get pregnant while on these drugs,