Delivering an HIV-infected woman's baby promptly after her water breaks appears to reduce her risk of passing on the AIDS virus during childbirth.
About 7,000 HIV-infected women give birth each year in the United States. Without treatment, about one in four transmits the virus to her child. However, taking the drug AZT during pregnancy reduces this risk by two-thirds.A study begun before AZT became routine therapy in pregnancy in 1994 shows that obstetrical practices also may play a role in HIV transmission.
The study found that if the baby is born more than four hours after the mother's water breaks, the risk of passing on the infection nearly doubles.
However, the researchers said they have no evidence that this delay in delivery makes any difference if infected mothers are already taking AZT.
"There is a possibility that in cases where AZT has not been used or cannot be used, the obstetrician may want to consider a Caesarean section in a woman who is going greater than four hours," said Dr. Sheldon H. Landesman, the study's principal author. He is from the State University of New York Health Science Center at Brooklyn in New York City.
His study, conducted on 525 HIV-infected women, was published this week in the New England Journal of Medicine. It found that the share of infected babies rose from 14 percent to 25 percent when delivery occurred more than four hours after the fetal membranes ruptured.
The researchers suspect that prolonged exposure to infected cervical and vaginal secretions account for the increased risk.
In an editorial in the journal, Drs. Daniel V. Landers and Richard L. Sweet of Magee-Womens Hospital in Pittsburgh said "every effort should be made to shorten the time between the rupture of membranes and delivery."
The study was conducted at hospitals in New York City, Chicago, San Juan, Puerto Rico, and Massachusetts.
Another study published last week in the British journal Lancet investigated whether washing out the birth canal with a mild soap solution lowers the risk. Doctors studied 7,000 women in Malawi, 30 percent of whom were infected with HIV.
Overall, the washing made no difference. However, it seemed to reduce the risk from 39 percent to 25 percent in those who delivered more than four hours after their membranes broke.