Fortunately, new study reveals that for some women who are severely overweight or obese, reducing some weight during pregnancy may be possible—and potentially advantageous (with a BMI of over 30). Losing weight, on the other hand, is not recommended for pregnant women who were at a healthy weight prior to pregnancy. A large study of more than 1,000 babies born in Canada found that those whose mothers lost more than 15 pounds during pregnancy had higher rates of asthma later in life. The American College of Obstetricians and Gynecologists advises pregnant women to avoid rapid weight loss. However, individuals should make their own decisions about diet and exercise during pregnancy; what's best for one person might not be right for another. For most women, maintaining a healthy weight throughout pregnancy is recommended. But if you're seriously overweight or obese, losing some weight through mild exercise and changing your eating habits may help you give birth to a baby who weighs more than 9 lbs 5 oz or experience other complications related to obesity. Your doctor will work with you to find something that's right for you.