Gideon Koren, a Toronto physician, tells of a 38- year-old woman whose doctor told her she would have to stop breast-feeding. She was passing an antidepressant, taken for postpartum depression, to her baby through her milk. Rather than stop breast-feeding, the woman, herself a physician, quit taking her medication. Soon after, she jumped into traffic while holding her baby.

More than once, says Baha Sibai, an obstetrics and gynecology professor in Cincinnati, he has seen pregnant women with artificial heart valves die from blood clots. Coumadin, a brand name for the blood-thinner warfarin, could have prevented the clots, but the women and their doctors had heard that the drug caused serious birth defects.

In both cases, the patients, and probably their physicians, were dangerously misinformed. Studies suggest that newer antidepressants, at least, are safe to use during breast- feeding. And Coumadin is widely used by pregnant women after the first trimester in other countries.

With images of limbless thalidomide babies forever burned into their consciousness, though, many pregnant women try to avoid taking any kind of medication, often at the urging of their doctors.

''Some of the greatest disasters in women's health have revolved around the impact of drugs on pregnant women,'' says Diana Zuckerman, executive director of the National Center for Policy Research for Women and Families in Washington, D.C.

The fears of women and doctors are understandable, considering the paucity of research, Zuckerman and other speakers noted last week at a government-sponsored conference on the subject. Participants in the meeting raised many of the same issues discussed at a government-sponsored conference on drug use during pregnancy back in 1994.

Concerned about opening themselves up to litigation, drugmakers generally have been reluctant to study the use of their products during pregnancy.

The federal government hasn't exactly encouraged such studies. For example, Department of Health and Human Services regulations require that the baby's father give his consent before a pregnant woman may participate in research.

''What we have been doing all of these years is emphasizing all the bad things that can happen from taking medicines in pregnancy,'' says Sibai, chairman of obstetrics and gynecology at the University of Cincinnati. ''Nobody explains to them what the implications are if they don't take the medicine.''

With serious, chronic diseases such as asthma, epilepsy and hypertension, the ramifications of not taking medicine can be grave. Severe asthma or hypertension during pregnancy can kill the mother as well as the fetus. Uncontrolled seizures can cause falls and other deadly accidents.

''Clearly, we have to balance the risks of the medication with the risks of the disease,'' says Michael Schatz, allergy chief at Kaiser Permanente Medical Center in San Diego. ''Our patients need to understand that it's not that there is no risk (in taking medication), but the risk is greater with uncontrolled disease.''

Relatively few drugs seriously imperil the health of a fetus, says Koren, a clinical pharmacologist at the Hospital for Sick Children in Toronto. The most notorious of the group is thalidomide, which has never been approved for use during pregnancy in the USA. In other countries, though, thousands of babies were born with limb deformities and other serious defects to women who took thalidomide for morning sickness in the 1950s and early 1960s.

Even when drugs increase the risk of birth defects, the chance of a problem is often remote, Sibai says. But neither the prescribing physicians nor the Food and Drug Administration-approved package inserts do a good job of putting the risks in context, he says. ''All of these package inserts emphasize things that are extremely rare.''

It's well known that lithium, a mood stabilizer used to treat manic-depression, can cause a heart defect called Ebstein's anomaly in babies born to women who took it while pregnant. What's not as well known, Koren says, is the fact that the risk is something like one in 5,000. ''Most people who need lithium find this very reassuring,'' he says.

Often, doctors withhold a drug through pregnancy and beyond -- long past the point when major fetal organs are formed, Sibai and Koren say. Coumadin can cause birth defects only in the first trimester, Sibai says. Corticosteroids, used to treat asthma, increase the risk of a cleft palate threefold to sixfold, but by the end of the first trimester, the palate is fused.

One of the few illnesses that are usually limited to the first trimester is the nausea and vomiting of pregnancy, or NVP, commonly -- albeit erroneously -- called morning sickness. Health Canada, that nation's equivalent of the FDA, has concluded that diclectin is the most effective drug for NVP.

But American women can't buy it.

Diclectin used to be sold under the brand name Bendectin in the USA and Canada. But as lawsuits claiming Bendectin caused birth defects began piling up, its maker, Merrell Dow Pharmaceuticals, stopped production in 1983. Although studies have confirmed that birth defects in children born to Bendectin users were chance occurrences, the drug's reputation suffered immeasurable harm.

Enter Duchesnay, a small Canadian pharmaceutical company that has been making and selling generic diclectin since 1975. Duchesnay faced a public relations nightmare when Bendectin came off the market.

Instead of bowing out, though, Duchesnay went on the offensive, consulting Koren and some of the other top experts on medications in pregnancy. All advised Duchesnay to keep selling diclectin. By spreading the message about diclectin's safety and effectiveness to physicians, Duchesnay was able to recover from the drop in sales that occurred after Bendectin's exit.

Now, says Duchesnay executive vicepresident Eric Gervais, the company is working with the FDA to bring diclectin to the USA. There's certainly a market for it, Gervais says. Each year in the USA, NVP accounts for 39,000 hospitalizations at a cost of $130 million.

''There's a huge therapeutic gap,'' Gervais says. ''Pregnant women do not have access to the drugs they need.''

To see more of USAToday.com, or to subscribe, go to http://www.usatoday.com ) Copyright 2000 USA TODAY, a division of Gannett Co. Inc.