Expected Weight Change in Newborns Revisited

Pediatricians expect newborns to regain their birth weight in approximately 10 days and thereafter gain between 0.5 and 2.0 ounces a day for the next several months. The American Academy of Pediatrics's Bright Futures Nutrition, 3rd Edition, states that most newborns will “regain their birth weight within 7 days.”

To test the validity of these estimates, investigators examined the records of more than 140,000 healthy infants born at ≥36 weeks' gestation in California hospitals between 2009 and 2013. Of these newborns, 76% were delivered vaginally and 24% by cesarean; 63% were exclusively breast-fed. Among the mothers, about 40% were white, 25% were Asian, and 25% were Hispanic. Nomograms were constructed to track the percentage weight gain f…