When Should I Gain the Most?
Although no two women are going to gain weight at exactly the same rate, there are some guidelines to follow: In the first trimester, you should gain 3.5 pounds if you're of normal weight. Underweight women need to gain 5 pounds, while overweight women should gain just 2.
In the second and third trimesters, your weight gain begins to speed up. An average-weight woman will gain about a pound a week between weeks 14 and 28. Underweight women should gain a little more than a pound a week during this time, and overweight women should try to limit their weekly gain to around one-half to three-quarters of a pound. Weight gain may drop off in the ninth month to only a pound or two as your body prepares for the birth.