Every pregnant woman in the country gets the same stern warning: Don't drink any alcohol.
But many of them still have a glass of wine at dinner, and they do it with the approval of their obstetrician/gynecologists.
So, what's the real deal? Is it dangerous to drink if you're expecting?
The country's medical establishment has long preached to pregnant women that they should avoid alcohol out of fear that it may harm the fetus.
But many obstetricians around the country counsel their patients that it's OK to have a few glasses of wine per week. And some of their patients take that advice -- more than 12 percent of pregnant women are social drinkers, according to government studies.
That discrepancy was exposed again last week when Oscar-winning actress Rachel Weisz, who recently gave birth to her first child, told fans that it was "fine" for expectant mothers to have a glass of wine after the first trimester.
The "Constant Gardener" star's recent comments caused an uproar among medical experts, some of whom condemned her advice as irresponsible.
In recent years, other celebrities such as Gwyneth Paltrow and Britney Spears have made headlines when they were photographed drinking while pregnant. Commentators were quick to call them unfit mothers-to-be.
"If you're pregnant and you drink alcohol in any amount, you take a risk that it could be causing harm to the fetus," said Tom Donaldson, the president of the National Organization on Fetal Alcohol Syndrome.
Because alcohol is a neurotoxin, it has the capacity to interfere with the development of the fetus and can be even more harmful than crack cocaine or other drugs, Donaldson explained.
"Why play Russian Roulette with your baby's health?" he said. "We say abstain from alcohol if you're pregnant or could be pregnant."
Similarly, the American Medical Association and the American College of Obstetricians and Gynecologists strongly recommend that expectant mothers avoid any alcohol during their pregnancy, warning that it could lead to mental and physical defects.
Concerned that the lack of public consensus on the issue was leading to risky behavior, then-Surgeon General Richard H. Carmona reissued a 25-year-old advisory last year about the dangers of drinking while pregnant.
Those stern warnings didn't dissuade Alexandra Atkins, a 38-year-old mother of two who lives in Manhattan, N.Y.
"I definitely drank once in a while, a glass of wine or a beer," she said. "My OB-GYN said it was OK to have an occasional drink -- and I have a healthy boy and girl."
Kate Licatta, a mother of three in New Canaan, Conn., says that her doctor said it was OK to have an occasional glass of wine.
"So I did, and I was less cautious with my second," Licatta said. "Not that I was taking it down every day with my third, but I drank twice a month, typically just wine or beer."
Plenty of obstetricians agree, arguing that it's safe to have a few glasses of wine or beer per week, as do some governments, including the British Health Ministry, which says that pregnant women can drink one or two units of alcohol -- glasses of wine, shots of liquor -- once or twice a week.
Robert K. Zurawin, a gynecologist at the Baylor College of Medicine in Houston, says that it's OK for a pregnant woman to have an occasional drink.
Asked about the warnings, he responded, "Give me a break! People who have a glass of wine on the weekend, it's not going to do any harm to the baby. In the first eight weeks when critical organs are forming, it's good to avoid alcohol and certainly smoking."
According to Michael S. Broder, a Los Angeles-based OB-GYN and the author of "The Panic-Free Pregnancy," the science is not definitive on the issue and the U.S. government and groups like the AMA are being overly cautious.
"They say that there isn't any evidence that drinking one glass of wine doesn't cause any real harm and that a safe alcohol level has never been established," he said. "But you don't prove things safe. The risk is so small, it's misleading to say that any alcohol will harm your baby."
Broder is concerned about the effect that these stern admonishments have on pregnant women, and he would like to see the government and the AMA issue more realistic advisories.
"The main harm coming from the guidelines is the guilt that it induces, to make pregnant women feel terrible if they have a single drink in a month."
Most OB-GYNs agree that the science is clear when it comes to heavy drinking or binge-drinking by pregnant women.
About 40,000 babies are born every year with some degree of alcohol-related damage, ranging from physical defects like small size and nearsightedness to mental defects like learning disabilities and hyperactivity.
And some studies have exposed dangers from moderate to light drinking by expectant mothers.
The children of mothers who had as little as one drink a week during pregnancy were more likely than the children of nondrinkers to exhibit behavior problems such as delinquency and aggressiveness, according to a 2001 study by Wayne State University researchers.
Despite these studies and the stern warnings, few pregnant women have changed their behavior. The ratio of moms-to-be drinking alcohol dropped slightly from 12.4 percent in 1999 to 2000 to 12.1 percent in 2005.
And the ratio of binge-drinkers remained the same at almost 4 percent.
Even some of the medical authorities acknowledge that the guidelines are overly prohibitive, given the science on the issue.
"You can't say that any alcohol, even the smallest amount, will lead to birth defects," said Donaldson of the National Organization on Fetal Alcohol Syndrome. "But we also don't want to say that one drink a week is OK, because then people naturally say, 'Oh, if one's all right, then three can't be bad.'"