Jane E. Brody / New York Times News Service

The thalidomide disaster of the early 1960s left thousands of babies with deformed limbs because their mothers innocently took a sleeping pill thought to be safe during pregnancy,

In its well-publicized wake, countless pregnant women avoided all medications, fearing that any drug they took could jeopardize their babies’ development. In the decades that followed, pregnancy-related hazards were linked to many medicinal substances: prescription and over-the-counter drugs and herbal remedies.

Now, however, the latest findings about drug use during pregnancy have ignited new concerns among experts.

Change isn’t always good

During the past 30 years, use of prescription drugs during the first trimester of pregnancy, when fetal organs are forming, has grown by more than 60 percent. About 90 percent of pregnant women take at least one medication, and 70 percent take at least one prescription drug, according to the Centers for Disease Control and Prevention.

Since the late 1970s, the proportion of pregnant women taking four or more medications has more than doubled. Nearly one woman in 10 takes an herbal remedy during the first trimester.

A growing number of pregnant women, naively assuming safety, self-medicate with over-the-counter drugs that once were sold only by prescription. The Food and Drug Administration estimates that 10 percent or more of birth defects result from medications taken during pregnancy.

“We seem to have forgotten as a society that drugs pose risks,” said Dr. Allen Mitchell, professor of epidemiology and pediatrics at Boston University Schools of Public Health and Medicine. “Many over-the-counter drugs were grandfathered in with no studies of their possible effects during pregnancy.”

Medical progress has contributed to the trend, Mitchell said. Various conditions, like depression, are now recognized as diseases that warrant treatment; drugs have been developed to treat conditions for which no treatment was previously available; and some conditions, like Type 2 diabetes and hypertension, have become more prevalent.

Now a new concern has surfaced: Bypassing their doctors, more women are using the Internet to determine whether the medicine they are taking or are about to take is safe for a fetus.

Led astray by websites ...

A study, published online last month in Pharmacoepidemiology and Drug Safety, of so-called “safe lists for medications in pregnancy” found that 25 websites had glaring inconsistencies and sometimes false reassurances or alarms based on “inadequate evidence.”

The report was prepared by Cheryl Broussard of the CDC with co-authors from Emory, Georgia State University, the University of British Columbia and the FDA.

“Among medications approved for use in the USA from 2000 to 2010, over 79 percent had no published human data on which to assess teratogenic risk (potential to cause birth defects), and 98 percent had insufficient published data to characterize such risk,” the authors wrote.

But that did not stop the 25 websites from characterizing 245 medications as “safe” for use by pregnant women, which “might encourage use of medications during pregnancy even when they are not necessary,” the authors suggested.

Furthermore, the information was sometimes contradictory.

“Twenty-two of the products listed as safe by one or more sites were stated not to be safe by one or more of the other sites,” the study found.

The question of timing was often ignored. A drug that could interfere with fetal organ development might be safe to take later in pregnancy. Or one (for example, ibuprofen) that is safe early in pregnancy could become a hazard later if it raises risks like excessive bleeding.

Only 13 sites encouraged pregnant women to consult their doctors before stopping or starting a medication.

... and sometimes by doctors

Doctors, too, are often poorly informed about pregnancy-related hazards of various drugs, the authors noted. One woman was advised to wean off an antidepressant before she became pregnant, but another was told to continue taking it throughout her pregnancy.

“In many instances the best bet is for mom to stay on her medication,” said Dr. Siobhan Dolan, an obstetrician and geneticist at Albert Einstein College of Medicine. She said that if a woman is depressed during pregnancy, her risk of postpartum depression is greater.

Dolan, who is author, with Alice Lesch Kelly, of the March of Dimes’ newest book, “Healthy Mom Healthy Baby,” emphasized the importance of weighing benefits and risks in deciding whether to take medication during pregnancy and which drugs to take.

“In anticipation of pregnancy, a woman taking more than one drug to treat her condition should try to get down to a single agent,” Dolan said in an interview. “Of the various medications available to treat a condition, is there a best choice — one least likely to cause a problem for either the baby or the mother?”

She cautioned against assuming that a remedy labeled “natural” or “herbal” is safe. Virtually none have been tested for safety in pregnancy.

Knowing what to avoid

Among medications a woman should be certain to avoid, in some cases starting three months before becoming pregnant, are isotretinoin (Accutane and others) for acne; valproic acid for seizures; lithium for bipolar disorder; tetracycline; and angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor antagonists for hypertension, Dolan said.

Broussard, who did the “safe lists” study, said, “We’ve heard about women seeing medications on these lists and deciding on their own that it’s OK to take them. Women who are pregnant or even thinking about getting pregnant should talk directly to their doctors before taking anything.”

A reliable online resource, Mitchell said, are fact sheets prepared by the Organization of Teratology Information Specialists, which are continually updated: www.otispregnancy.org.