HOUSTON -

Raw sushi, coffee and wine are things many pregnant women crave. Doctors often tell pregnant women that they should be off limits, but do they need to be?

"I'm a big sushi fan, so I've always wanted sushi," said Patty Holmes, a mother and member of the Houston Sushi Club. "But it's such a challenge because when you're pregnant there are all these things they tell you not to have."

Holmes recently gave birth to her son David Christian. When she was pregnant, her cravings for sushi were hard to resist. But Holmes knew raw sushi was a no-no.

"Mostly cooked fish, obviously. That's the safest way to go," said Holmes.

But that conventional wisdom is being questioned by Emily Oster, who wrote, "Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong-and What You Really Need to Know."

In her book, Oster says three sins of pregnancy -- raw sushi, wine and coffee -- shouldn't be off limits.

"I think on the coffee, the evidence suggests certainty in moderation, 200 milligrams a day. That's probably two little cups, said Oster. "Most women should feel comfortable having sushi from a reputable source, the same kind of sushi you would have when you're not pregnant."

And what about wine?

"On alcohol, this has clearly hit a nerve," said Oster. "Alcohol: no more than two drinks a week in the first trimester and no more than one drink a day in later trimesters."

Oster is a mother but not a doctor. She's an associate professor of economics at the University of Chicago.

"My job is really about analyzing data and figuring out what it can tell us," said Oster.

"There are some studies that have been done with extreme amounts of coffee that have shown an increased risk for miscarriage and so we feel drinking coffee in moderation, about a cup, is a safe amount," said Dr. Cristina Perez, an OB/GYN with The Women's Specialists of Houston at Texas Children's Pavilion for Women.

When it comes to alcohol, Perez said, "I think that we'll never be able to study how much alcohol is safe in pregnancy because they won't do a study testing which babies end up having fetal alcohol syndrome."

Perez said it's okay to eat cooked sushi if you avoid fish high in mercury.

"With raw sushi, we recommend that pregnant women avoid [it] because there is an increased risk for food-borne illness," said Perez.

The Houston Sushi Club says the safest sushi dishes while pregnant are a California roll without the fish eggs, Tamagoyaki, which is a cooked egg omelet, cooked eel or smoked salmon. You could also go for a rock and roll, which is fried shrimp, or a vegetarian roll.

"Pregnancy is not a good time to try the latest, hottest, Japanese food trend," said Holmes. "Wait until you're done having kids to go and try those."