Breast-fed Newborns: How Much Weight Loss Is Normal?

Diedtra Henderson

December 01, 2014

Exclusively breast-fed newborns typically lost as much as 10% or more of their birth weight before beginning to gain again in the first days after birth, according to a recent study. By 48 hours, almost 5% of babies born vaginally and 10% of those born by cesarean delivery lost at least 10% of their birth weight. By 72 hours, 25% of cesarean delivered infants lost at least 10% of their birth weight. These metrics may help identify babies with steeper weight loss trajectories that could increase morbidity risk.

Valerie J. Flaherman, MD, MPH, from the Department of Pediatrics and the Department of Epidemiology and Biostatistics, School of Medicine, University of California, San Francisco, and colleagues report the findings of their study in an article published online December 1 in Pediatrics.

According to the authors, 60% of newborns in the United States are breast-fed exclusively in the first 2 days after birth, in keeping with recommendations from a number of expert organizations, including the American Academy of Pediatrics. Most of those infants lose weight daily, but a small number of infants suffer complications from excessive weight loss, including hyperbilirubinemia and dehydration.

"These results provide the first graphical depiction of hourly weight loss for exclusively breastfed newborns from a large, diverse population," Dr Flaherman and coauthors write. "Because weight changes steadily throughout the birth hospitalization and is measured at varied intervals from the hour of birth, these new nomograms should substantially aid medical management by allowing clinicians and lactation support providers to categorize newborn weight loss and calibrate decision-making to reflect hour of age."

The authors note that hour-by-hour bilirubin levels, tracked to guard against jaundice, have been incorporated into practice guidelines. To provide a similar type of nomogram for neonate weight loss in exclusively breast-fed newborns, Dr Flaherman and coauthors studied data from 108,907 newborns born at 36 weeks' gestation at Northern California Kaiser Permanente hospitals from January 1, 2009, through December 31, 2013.

Some 83,433 (76.6%) of the neonates were delivered vaginally, whereas 25,474 (23.4%) were born by cesarean delivery. For the 97.3% of mothers who had race or ethnicity noted, 43% were white non-Hispanic, 24% were Hispanic, 24% were Asian, and 7% were black non-Hispanic.

The researchers excluded infants who had received level 2 or 3 care and infants whose steep weight gain or loss was "implausible." Because infants delivered vaginally are hospitalized for shorter periods, they determined weight loss percentile from 6 to 72 hours compared with 6 to 96 hours for cesarean births.

Weight loss differences by delivery type were clear within 24 hours of birth, the authors write. Neonates delivered vaginally experienced a median weight loss of 4.2%, 7.1%, and 6.4%, respectively, at 24, 48, and 72 hours of age. That compared with median weight loss among infants born by cesarean delivery of 4.9%, 8.0%, 8.6%, and 5.8%, respectively, at 24, 48, 72, and 96 hours after delivery.

In an accompanying editorial, James A. Taylor, MD, and Elizabeth A. Simpson, MD, applauded the researchers for their "elegant methodology" and for providing "much needed data" to help provide instruction to the 79% of mothers who now breast-feed and to clinicians managing complications.

"With the nomograms, clinicians can plot the percent weight loss for a neonate at a specific age and determine, with precision, whether this percentage is normal for a breastfed newborn (eg, at the 50th percentile) or excessive (eg, ≥95th percentile). Although these assessments have been done informally for many years in newborn nurseries, the new nomograms provide much-needed rigor," the editorialists write.

Dr Taylor, from the University of Washington Department of Pediatrics, Seattle, and Dr Simpson, from the Department of Pediatrics, Children's Mercy Hospital, Kansas City, Missouri, call the weight loss seen among infants delivered by cesarean "jarring" but suggest that infants delivered vaginally also continued to shed weight postdischarge, when weight loss data were not collected systematically. Although they call the project a good first step, they call for strengthening the evidence base by using the nomograms "to characterize weight loss in a group of newborns and link specific patterns of weight loss with relevant outcomes."

Dr Flaherman and colleagues conclude by saying their "curves demonstrate that expected weight loss differs substantially by method of delivery and that this difference persists over time. Our results also show that weight loss ≥10% of birth weight is common and often occurs earlier in the postnatal course than previously documented."

Financial support for the study was provided by the Department of Health and Human Services and the National Institutes of Health. The study authors and the commentators have disclosed no relevant financial relationships.

Pediatrics. Published online December 1, 2014.

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