AZT Urged for AIDS-Infected Mothers' Newborns

BOSTON (Reuter) - AZT drug treatments can limit the spread of the AIDS virus from a mother to her newborn baby but the reason it works remains unclear, according to a study in Thursday's New England Journal of Medicine.

The study led a team of doctors to recommend AZT treatment for any pregnant woman with the AIDS virus, regardless of how much virus material can be detected in the blood.

Doctors do not understand how the AIDS virus is passed to a baby. Conventional wisdom holds that 50 to 70 percent of all AIDS babies acquire the virus around the time of birth but it is unclear whether a child becomes infected in the womb or during delivery.

In the past year or so, doctors have observed that the disease seems to progress faster in people who have higher levels of the virus in their blood.

A group of researchers led by Dr. Rhoda Sperling of the Mount Sinai School of Medicine in New York City decided to see if virus levels in the mother influenced the chances of her infant being infected with the AIDS virus. They found that the higher the levels of the virus in a mother's blood the greater the likelihood the disease would be passed on to the baby.

But there were plenty of exceptions to that rule. In fact, when they looked closely at their data, they found that the ability to reduce the amount of virus in the blood is only partly responsible for the ability of AZT to block the spread of the virus to a newborn.

Sperling's team said there was no evidence that even a tiny amount of virus in the blood is safe. "Our data do not suggest that there is an absolute plasma RNA level below which transmission does not occur," they said.

The group also expanded on work, reported two years ago, showing that AZT is effective at preventing the spread of the AIDS virus from a mother to her newborn child in 363 cases. By following 402 infants for 18 months, they confirmed that AZT, made by Glaxo Wellcome and also known as zidovudine, cuts the infection rate among newborns by nearly two thirds.

They reported that 7.6 percent of the babies whose mothers had received AZT became infected themselves compared with 22.6 percent whose mothers had been treated with a placebo.