Weight loss in newborns may not be caused by lack of breast milk

15^th August 2011 - A newborn baby's weight loss is often used to determine how well the baby is breastfeeding. Concern about a baby who loses too much weight just after birth may result in advice to supplement breastfeeding with formula. However, new research shows that in women who receive IV fluids during labour, some of a newborn's initial weight loss may be due to the infant regulating its hydration, and not because of a lack of breast milk.

In their study, published in the International Breastfeeding Journal on 15 August 2011, a group of Canadian researchers looked at relationships between the IV fluids a mother received during labour (or prior to her caesarean section), neonatal output (measured by wet nappy weight) and newborn weight loss. They found that during the first 24 hours after birth, there was a positive association both between the IV fluids given to mothers before birth and neonatal urine output, and between the neonatal output and newborn weight loss. At 60 hours after birth, the time of the average lowest weight, there was a positive relationship between the mother's 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 from 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," she explained.

24 hour post-birth measurement advised

Professor Noel-Weiss added: "We should reconsider the practice of using birth weight as the baseline when calculating newborn weight loss in the first few days following birth. For mothers and their breastfed babies, accurate assessment of weight loss is important. Although more research is needed, based on our findings we would recommend using weight measured at 24 hours post birth as a baseline."

In the UK, the Department of Health has combined World Health Organization (WHO) standards with UK birth data, backed by the Royal College of Paediatrics and Child Health. Whether breastfed or formula fed, the current recommendation is for a baby to be weighed within a week of birth to assess the baby's feeding. If the baby recovers his or her birth weight, it indicates that the child is feeding effectively. According to the Department of Health, most babies lose some weight after birth, and of these 80% will regain it by two weeks of age.