When you complete 37 weeks of pregnancy, your baby should be above 2.5 Kg at birth. The first ten days your baby loses weight and regains the birth weight at around 10 days of age. Then starts picking up. If your baby gains 20 ??“ 30 grams per day will be sufficient. Roughly, at 5 months your baby doubles the birth weight, triples at one year and quadruples at 2 years of age. When your baby does not meet this requirement seek doctor's advice.