Traditional teaching: newborns regain birth weight by 10 days of life, then 0.5 – 2.0 oz per day thereafter for the first two months.
n = 140,000 healthy newborns born >36 weeks of gestation in California between 2009-2013.
76% vaginal births, 24% C-section.
40% white, 25% Asian, 25% Hispanic.
“Results were as follows:
Early weight change was similar with both delivery methods; the 50th-percentile nadir in weight loss for vaginal- and cesarean-delivered infants was at 61 and 68 hours, respectively.
Weight gain was faster for smaller birth weight newborns; about half of those with birth weights of 2000–2999 g regained their birth weight at 8 or 9 days (for vaginal and cesarean deliveries, respectively), whereas about half of those with birth weights of 4000 to 5000 g regained their birth weight by 10 or 12 days, respectively.
A substantial portion of newborns failed to reach their birth weight by 14 days (14% for vaginal deliveries and 24% for cesarean).” (NEJM Journal Watch)
Reference: Paul IM et al. Pediatrics 2016 Dec.