BALTIMORE -- When women become pregnant, one thing that many of them worry about is gaining too much weight.

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In fact, some women think about going low-carb to make sure that doesn't happen, but one doctor said that's not a great idea.

Denise Beach Davis, 37, is expecting her second child in December.

"(I'm afraid of) weight gain," said Davis. "I just really don't want to gain 80 pounds, even 40 pounds."

But Dr. Jean Hundley from Mercy Medical Center in Baltimore does not recommend dieting during pregnancy. Hundley said women should be careful about what they eat.

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She said a low-carb diet can recommend 20 grams of carbohydrates a day, but in pregnancy, you need 150 grams, and there's a real danger if you go into high-protein ketosis.

"Ketosis can affect the fetal brain, leading to mental retardation down the road, so it's very important for the patients to get adequate carbohydrates during pregnancy," said Hundley.

So Davis is just trying to eat a well-balanced diet -- plenty of whole grains, fruits, veggies and protein.

"I just try to do the best I can, but it's not easy," said Davis. "Sometimes I want to eat everything, but I don't."

The carbohydrates that pregnant women should limit are the refined ones -- doughnuts, sugars, cakes and all the goodies.