Weight gain
also see Height gain, Birth Weight

• During first 3 days of life, weight decreases 5-10% then back to birth weight by 1-2 weeks.
• During first three months, expect to gain 1 oz of weight per day (30 grams/day).
• During 3-6 moth old, growth slows to 20 g/day.
• During 6-12 m/o, 10 g/day
• Birth weight:
  • doubles within 4-5 months
  • x3 within a year (a one year old weighs about 10 kg or 20-25 pounds)
  • x4 by 2 years.
• Rule of 3's for a three year old: 30 pounds, 3 feet tall
   

Estimating weight: 1/2 month + 3.5 kg  or 2(year) +12 kg

Different organs grow at different rates. For instance, the reproductive system has a brief growth spurt just after birth, then changes very little until just before puberty. In contrast, the brain grows almost exclusively during the early years of life. At birth, the brain is one fourth of its future adult size. By 1 year, the brain is three fourths of its adult size. The kidneys function at the adult level by the end of the first year.