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OTTAWA, August 15, 2011  —  New research at the University of Ottawa shows that some of the initial weight loss in breastfed newborns may be due to increased neonatal output and not related to a lack of breastfeeding.

A newborn's weight loss is often used to determine how well a baby is breastfeeding. Too much weight loss may cause concern and result in supplementation with formula. However, many women receive IV fluids during labour, and new research published in BioMed Central's open access International Breastfeeding Journal shows that some of a newborn's initial weight loss may be due to the infant regulating its hydration, and not related to a lack of breast milk.

A group of Canadian researchers looked at relationships among the IV fluids a mother received during labour (or prior to her caesarean section), neonatal output (measured by diaper weight) and newborn weight loss. They found positive relationships both between the amount of IV fluids given to mothers before birth and neonatal output and between neonatal output and newborn weight loss during the first 24 hours following birth. At 60 hours post birth, the time of the lowest average weight, there was a positive relationship between the amount of maternal IV fluids and newborn weight loss.

"Nurses, midwives, lactation consultants and doctors have long wondered why some babies lose substantially more weight than others even though all babies get small amounts to eat in the beginning," said principal investigator Professor Joy Noel-Weiss of the School of Nursing at the University of Ottawa's Faculty of Health Sciences. "It appears neonates exposed to increased fluids before birth might be born overhydrated, requiring the baby to regulate his or her fluid levels during the first 24 hours after birth."

Professor Noel-Weiss explained that we should reconsider the practice of using birth weight as the baseline when calculating newborn weight loss in the first few days following birth. She suggests, “Although more research is needed, based on these findings, we would recommend using a weight measured at 24 hours post birth as a baseline."

In addition to this article, the researchers have provided a standardized protocol for clinicians to collect and analyze data about newborn weight loss in the clinicians’ maternity setting, in the hope that this protocol will help them make informed decisions when assessing weight change in newborns.