2-weeks, 6-months, and 12-months are the milestone markers for birth weight measurements.  A child should:

• Regain their birth weight by 2-weeks

• Double their birth weight by 6-months

• Triple their birth weight by 12-months

Reference

McGahren ED, Wilson WG.  Pediatric Recall.  4th ed. Baltimore, MD.  LWW. 2010.