Federal regulators don't know if the abortion pill increases the likelihood of infection by a rare but deadly bacterium that killed four California women, a health official said Wednesday at a congressional hearing convened by RU-486 opponents.

The four women all died from infection by Clostridium sordellii after they took the pill and underwent abortions. Their deaths are among a handful of fatal cases involving C. sordellii in women, including others who died after childbirth or suffering miscarriages.

The drug, mifepristone, works by blocking a hormone required to sustain a pregnancy. When followed two days later by another medicine, misoprostol, to induce contractions, a pregnancy is terminated.

Opponents of RU-486 have pointed to the post-abortion deaths in pushing for a ban on sales of the pill, which gained Food and Drug Administration approval in 2000. It's not clear how the two may be linked, an FDA official told the House subcommittee on Criminal Justice, Drug Policy and Human Resources.

"It is not possible at this time to determine whether the current mifepristone/misoprostol regimen for abortion results in increased risk for C. sordellii infection," said Dr. Janet Woodcock, the FDA's deputy commissioner for operations.

Some believe the drug suppresses the immune system. But proponents of the drug say the infections may be the vanguard of an emerging obstetrical threat that the bug poses.

Rep. Mark Souder (news, bio, voting record), R-Ind., convened the hearing to examine whether the drug demonstrated "a low standard for women's health." Souder cited FDA reports of 950 cases of adverse reactions to the pill, including 18 cases of severe infections in women who required hospitalization and antibiotics, in making the case that the drug posed a threat to women's health.

"I would like to ban abortion but this is not about abortion. You can't ban abortion. This is a health question," Souder said in response to criticism leveled by panel Democrats that he was motivated by ideology and not science in convening the hearing.

"That's the question: Is there a link between those deaths and this drug? That is a scientific question, not an ideological one," said Rep. Henry Waxman (news, bio, voting record), D-Calif., adding that the question should be left to the FDA and scientists.

Nearly 600,000 women in the U.S. have used Mifeprex — the brand name for Mifepristone — since its approval in 2000, according to Danco Laboratories. Roughly another 1.5 million women in Europe have used the drug.

Rep. Jean Schmidt, R-Ohio, referred to the limited number of serious but nonfatal fungal infections in contact lens wearers, which led to this week's recall of a Bausch & Lomb cleaning solution, in demanding that the FDA pull the pill.

"We're real careful about other things about your body, but with women's bodies it seems we're not that careful," Schmidt said.