the baby weight is while born 2.8 kg .. it's been 40 days still bby weight 2.9 kg is it normal ? feeding only mother's milk

A. A healthy newborn is expected to lose 7% to 10% of the birth weight, but should regain that weight within the first 2 weeks or so after birth. During their first month, most newborns gain weight at a rate of about 1 ounce (30 grams) per day.