CHICAGO (AP) — Pregnancy started out rough for Leslie Siu. Morning sickness and migraines had her reeling and barely able to function at a demanding New York marketing job, so like rising numbers of U.S. mothers-to-be, she turned to marijuana.

“l was finally able to get out from under my work desk,” said Siu, who later started her own pot company and says her daughter, now 4, is thriving.

There’s no proof that cannabis can relieve morning sickness, and mainstream medicine advises against use in pregnancy because of studies suggesting it might cause premature birth, low birthweight and infant brain deficits. But the National Institute on Drug Abuse is pressing for more solid evidence. Many of those studies were in animals or complicated by marijuana users’ other habits and lifestyles.

“I don’t want us to cry wolf,” said Dr. Nora Volkow, the agency’s director. “We have to do these studies in a way that can identify risks.”

With nearly $200,000 from her agency, University of Washington scientists in Seattle are seeking clearer answers in a new study investigating potential effects on infants’ brains. The agency is supporting three similar studies in other states.

In Seattle, they’re enrolling pregnant women during their first trimester who are already using marijuana for morning sickness.  [Read More @ CBS Boston]