A: Typically, a pregnant woman gains 3 to 5 lbs. during the first trimester. This is not always the case, however. Sometimes, women suffer from extreme nausea, food and smell aversions, and vomiting. Small amounts of weight loss can be ok if you are suffering from any of the above symptoms. Larger amounts of weight loss, specifically more than 5% of your pre-pregnancy weight, can be dangerous for your fetus. If you are concerned about your weight loss, the best thing to do is inform your practitioner and ask for different strategies to gain appropriate amounts of weight.