The researchers recorded the amount of oral and IV fluids mothers were receiving while in labor or before a C-section, and had parents weigh their babies every twelve hours in the weeks immediately after delivery. They found that the more fluids moms got in the two hours before delivery, the more weight their baby lost post-partum.
So what does that tell us about birth weight? It might be artificially high because of those fluids mom took in, say the authors. "Intuitively, clinicians and parents want to see the neonate return to birth weight," they write in this month's issue of the International Breastfeeding Journal. But, "if it is inflated, then the expectations for a return to birth weight in the first days are questionable."
Instead of using birth weight as a baseline, the authors suggest, use the weight of the baby when it's one day old. That gives the baby's weight time to stabilize.