Women's Biggest Pregnancy Fears

What's the biggest worry women have when they're pregnant?

CBS News medical correspondent Dr. Jennifer Ashton, an obstetrician and gynecologist, said one of those worries is weight gain.

She cited a poll by the March of Dimes Foundation.

What's the appropriate amount of weight gain for pregnant women?

Ashton said it's around 25 pounds for the average woman. And for an overweight woman, weight gain should actually be -- zero pounds.

"The baby takes weight from the mom," she said. "(She) can have a healthy baby without gaining more than a couple pounds."

Ashton said overweight women should be observed, saying, "We have to follow them, and they can have a healthy full-term normal sized baby without putting 50 pounds on for themselves."

Another concern for women is fish consumption. What is safe, and how much can women eat?

The two concerns for pregnant women are mercury and parasites. Ashton said tuna and shark can contain mercury, so you should limit your intake to six to 12 ounces a week.

Another pregnancy concern is stress. But how does stress affect a pregnancy?

"Every pregnant woman is under stress at some point,"Ashton said. "Mild stress is good for the pregnancy. It releases good hormones for the woman and baby. Severe stress -- talking about catastrophes like 9/11 or earthquakes -- have been associated with lower birth weight babies or shorter pregnancy durations."