Pregnancy Wisdom Questioned: Are Alcohol, Caffeine Really Off Limits?

Author of "Expecting Better" Emily Oster says women can do more than they think while pregnant.
4:11 | 08/12/13

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Transcript for Pregnancy Wisdom Questioned: Are Alcohol, Caffeine Really Off Limits?
pregnancy. What is really on or off-limits for women who are expecting? For years, alcohol, caffeine, exercise, what you should and shouldn't be doing. A new book, called "expecting better." It looked at research. Paula faris has more. Reporter: With all the rules and questions, how can any woman truly know what to expect when you're expecting. Who is this guy? Now, one chicago economist says some of the age-old pregnancy DOs AND DON'Ts MAY NOT BE TRUE. Emily oster, author of "expecting better" came to her own conclusion. I found the conflicting advi adviceover wom-- advice overwhelming. Reporter: Rule number one. Maybe glass of wine a day is not dangerous. Reporter: Rule number two, pregnant women should cut out the cup of joe. Oster says, not true. I found caffeine in moderation is also fine. Two to four cups a day depenning on how cautiou want to be. Reporter: Rule three, adding life to your yard could harm your baby. Some increase in birth defect ifs you do outdoor gardening while present. Reporter: She's not a medical doctor. Many obstetricians disagree with her collective findings. There is to amount of alcohol in pregnancy that should be considered safe. Anything the mother ingests goes to the fetus. Reporter: Oster hopes pregnant women draw their on conclusions. I think it's important for women to take their pregnancies into their own hands and make good decisions for themselves. Emily oster's book, "expecting better" why the conventional pregnancy wisdom is wrong and what you really need to know hits the shelves august 20th. We bring in dr. Jennifer to talk to us. It's important for people to understand, there's a lot more to practicing medicine than crunching numbers. What are the risks of doing something? Of not doing it? The benefits of doing something? The benefits of not doing it? And then some options. The alcohol thing. For so many women, it's good-bye to alcohol for nine months. That is a bold statement that you could have up to one glass a day? To say the least. And obstetricians and midwifes are going to be doing damage control. Fun fact, we used to use alcohol to stop preterm contractions. There may be contradictory data about the risks. But there is no data about the benefits for a baby. Since it's optional, a doctor would say, if you want one or two drinks at the end of your pregnancy, it's okay. But one drink a day? Exercise. If you want to exercise, pregnant or nonpregnant. Okay? The woman makes the decision. Happy to have a role right there. There you go, josh. The men have a big role if pregnancy, josh, fyi. I find out late in the game. Up next, two-time nba champ LeBRON JAMES. You remember the wonderful moment this year's espy's in

This transcript has been automatically generated and may not be 100% accurate.

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