A rare germ that killed four California women who took the abortion pill RU-486 has been implicated in the deaths of even more women following childbirth or miscarriage, broadening the debate beyond abortion on the eve of a meeting to examine the bacterial mystery.

While the abortion link has grabbed the most attention, Clostridium sordellii has killed at least 11 other women, women's health experts said in interviews. That's more than twice as many as have died of infection after taking the abortion pill, also called Mifeprex or mifepristone.

The numbers suggest the bacterium's threat, while still limited, could be broader than previously thought.

"That's a critical question: Is this association between use of Mifeprex and infection with C. sordellii ... or is it something more general?" asked Susan Wood, the former top women's health official at the Food and Drug Administration. She thinks it's the latter.

Scientists from the Centers for Disease Control and Prevention, National Institutes of Health and FDA are meeting Thursday in Atlanta to decide what research is needed to better understand the emerging threat posed by C. sordellii and a second bacterium, Clostridium difficile. The second germ is not linked to the abortion pill but is growing in prevalence in hospitals and nursing homes, and is increasingly resistant to antibiotics.

C. sordellii has been linked to four abortion pill deaths; a fifth is being investigated.

Opponents of the abortion pill have seized on those deaths — along with hundreds more complications after pill-induced abortions — to call for pulling Mifeprex from the market. A congressional hearing is set for next week, where Monty Patterson, a California man whose 18-year-old daughter died in 2003 after taking the abortion pill, is expected to renew his call for a ban. Also expected to testify is a doctor from the American Association of Pro Life Obstetricians and Gynecologists.

"We'll let the scientists talk about the science but we already see the drug is killing women and causing a lot of adverse events," said Michelle Gress, counsel to the subcommittee holding the hearing. A Senate bill proposes suspending sales of RU-486 while the Government Accountability Office reviews how the FDA approved the pill.

The drug's manufacturer, Danco Laboratories, has repeatedly said the pill is safe.

The risk posed by C. sordellii remains murky. In studies and letters published in the New England Journal of Medicine in December and April, researchers detail eight other women who died of C. sordellii infection after giving birth, vaginally or by Caesarean section. Also counted are two additional deaths following miscarriages and a final death linked to infection during the woman's menstrual period.

"That's 11 other cases that have nothing to do with abortion — they're other obstetric events," said Dr. Beverly Winikoff, a women's health advocate who worked to bring the abortion pill to the United States.

The abortion pill might suppress the immune system, which would increase susceptibility to bacteria already present in the vaginal canal, according to a study published last year by Dr. Ralph Miech of Brown University.

However, pregnancy naturally suppresses the immune system, too. Dilation of the cervix, whether because of abortion, childbirth or miscarriage, also may let bacteria penetrate deeper into the body, Miech and others have proposed.

Various species of Clostridium bacteria are found naturally in the vaginas of an estimated 4 percent to 10 percent of all women. C. sordellii in particular accounts for perhaps just 1 percent of those bacteria, meaning that roughly one in 1,000 women may harbor the bug. Winikoff said some doctors speculate that the presence of placental or fetal tissue in the vagina following childbirth, miscarriage or abortion could provide the medium the bug requires to flourish.

"It's a vulnerability of the female genital tract. What unleashes it, we don't know. Who's at risk? We also don't know," Winikoff said.

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. All four California women inserted the second drug into the vagina, a method of use not endorsed by the FDA, which urges that it be swallowed instead.

Dr. Didier Sicard, a French physician and ethicist whose 34-year-old daughter was the fourth fatality, recommended that all women should be administered antibiotics when undergoing a pill-induced abortion.

In addition to the highly publicized deaths, the FDA said it has received reports of 950 cases of adverse reactions to the pill, including 18 cases of severe infections in women who required hospitalization and antibiotics.

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