Question: how much weight should baby gain by 12 weeks?
Answer: Expect your baby to double his or her birth weight by about age 5 months. From ages 6 to 12 months, a baby might grow 3/8 inch (about 1 centimeter) a month and gain 3 to 5 ounces (about 85 to 140 grams) a week. Expect your baby to triple his or her birth weight by about age 1 year.