In the intervening decades, the treatment is widely believed to have undergone more scrutiny for safety than any other drug used during pregnancy.
"There's been a lot of buzz about this. Nothing better has come along" to treat morning sickness in those 30 years, said Dr. Edward McCabe, medical director for the March of Dimes, who welcomed the step.
"We know safety-wise, there's zero question," said Dr. Gary Hankins of the University of Texas Medical Branch in Galveston, who headed one of the company-financed studies of Diclegis that led to its approval.
U.S. sales of Diclegis are expected to begin in early June, according to Canada-based manufacturer Duchesnay Inc. The company has long sold a generic version of the pill in Canada under yet another name, Diclectin.
For all the names, the main ingredients are the same: Vitamin B6 plus the over-the-counter antihistamine doxylamine, found in the sleep aid Unisom. U.S. obstetricians have long told nauseated pregnant women how to mix up the right dose themselves.
In fact, in 2004 the American College of Obstetricians and Gynecologists issued guidelines calling the combination a first-line therapy.
The difference that prescription-only Diclegis would offer: Combining both ingredients with a delayed-release coating designed to help women take a daily dose before their nausea sets in.
The return of an FDA-cleared treatment is needed, said ACOG spokesman Dr. Jeffrey Ecker, an obstetrician at Massachusetts General Hospital who wasn't involved in the study of Diclegis.
"It's not magic," Ecker cautioned, saying few women see their symptoms completely disappear with the medication. "But for some it allows them to be much more functional."
In Hankins' study, about 260 U.S. women with morning sickness were given either Diclegis or a dummy pill for two weeks. The Diclegis users missed on average 1 1/2 fewer days of work than their counterparts.
Duchesnay wouldn't reveal a U.S. price.
About three-quarters of women experience at least some nausea and vomiting with the hormonal surges of early pregnancy. Although it often occurs upon waking, some women have trouble all day. It usually ends by the second trimester.
About 1 percent of women undergo dangerously severe vomiting called hyperemesis gravidarum, the condition that made headlines last December when in Britain, Prince William's wife Kate was briefly hospitalized.
An initial version of Bendectin began selling in 1956, and 33 million women around the world were estimated to have taken it before the lawsuits began. At the time, the FDA continued to call the drug safe; appeals courts ruled in favor of Bendectin maker Merrell Dow Pharmaceuticals; and eventually a U.S. Supreme Court decision would render continuing suits unlikely. But Merrell Dow declared the litigation cost too high, and quit making Bendectin in 1983.
What happened? The government estimates 1 in 33 babies are born with birth defects regardless of medication use during pregnancy, and studies eventually concluded that Bendectin didn't increase that baseline risk. McCabe of the March of Dimes says it's important to recognize that when a drug is widely used in pregnancy, some babies will be born with birth defects that are a coincidence.
Doctors advise trying some other steps before turning to medication for morning sickness: Eat protein snacks before bed. Nibble crackers or sip ginger ale before getting out of bed. Eat frequent small meals. Avoid nausea-triggering odors.
When that doesn't work, Ecker says vitamin B6 alone helps some women. His next step is the B6-and-antihistamine combination that will form Diclegis. A next-step option includes the drug Zofran, normally used to treat nausea from cancer therapy.