Question: how much weight should a newborn gain by 3 weeks?
Answer: During their first month, most newborns gain weight at a rate of about 1 ounce (30 grams) per day. They generally grow in height about 1 to 1½ inches (2.54 to 3.81 centimeters) during the first month. Many newborns go through a period of rapid growth when they are 7 to 10 days old and again at 3 and 6 weeks.