The nation's top public health agency on Thursday changed its guidance for HIV-infected men who want to father children, saying there's now enough evidence that a lab technique that removes the virus is a safe option.

For many years, the Centers for Disease Control and Prevention said it was too risky for infected men to have unprotected sex with uninfected women since that is one way the virus spreads. Infection of the baby is considered possible, but far less likely, CDC officials said.

More recently, the agency said some couples can try to conceive if the man has been taking virus-suppressing HIV medications and the woman takes a drug that protects against infection.

But it's been slow to OK a technique called "sperm washing," which has been around for decades and endorsed by other medical organizations. It involves separating sperm from infected cells in seminal fluid and using the sperm for artificial insemination or in vitro fertilization.

The agency wanted substantial evidence that women weren't becoming infected from washed sperm. After reviewing nearly 4,000 cases worldwide, it's become clear women are not, said the CDC's Dr. Denise Jamieson.

The technique can cost $10,000 or more with in vitro fertilization, and the price has been more of a deterrent than the CDC's slowness to endorse it, said Dr. William R. Short of the University of Pennsylvania, who treats such couples. But the CDC's update probably will help more couples feel comfortable about trying to conceive, he said.