THE NEW DRUG THERAPIES meant a big change in thinking for a Boston couple named Charley and Barbara. Charley has been HIV-positive for a dozen years. Barbara is not. With medications, Charlie's health is relatively good, so for the first time the couple can plan life more than just a few weeks out. "That presented us an opportunity to be normal, to be like another couple," Barbara says. Charlie adds, "Thinking about the possibility of having children is very exciting."

Barbara and Charlie are both school teachers in their forties. Charlie was HIV-positive when they married. The prospect of Charlie living long enough to watch their potential children grow seemed to Barbara like an unexpected gift.

"I had thoughts that other people do, of what would this [child] feel like growing inside me. Not to have a child, but to have our child."

Not so fast.

If Barbara and Charley have unprotected sex just once, the odds are she won't get HIV. But there's certainly no guarantee. HIV experts say that at any given time, a man may have more of the virus in his semen than other times. At any given time, a women may be more likely than usual to get the infection because of genital abrasions or other factors. And few women get pregnant on the first try.