What is the normal weight loss range for a newborn in the first week of life and when should supplementation be considered?

From the Guidelines

Newborns typically lose 5-10% of their birth weight during the first week of life, with breastfed babies often losing closer to 7-10% and formula-fed infants losing around 5%. This weight loss is normal and occurs due to fluid shifts, limited initial milk intake, and passage of meconium.

Key Points to Consider

• Supplementation should be considered when weight loss exceeds 10% of birth weight, when there are signs of dehydration (such as decreased urination, dry mucous membranes, or lethargy), or when the infant shows excessive hunger despite frequent feeding 1.
• For breastfed babies, supplementation options include expressed breast milk (preferred), donor human milk, or formula, typically offered after breastfeeding attempts.
• The amount of supplementation varies by age and weight but generally starts at 10-15 mL per feeding for newborns.
• Most healthy babies begin regaining weight by days 4-5 and should return to their birth weight by 10-14 days of age.
• Regular weight checks are important during this period to ensure the baby is following an appropriate growth trajectory.

Evidence-Based Recommendations

• According to the espghan/espen/espr/cspen guidelines on pediatric parenteral nutrition, in term neonates, postnatal weight loss generally occurs during the first 2-5 days of life and should not usually exceed 10% of birth weight 1.
• In ELBW and VLBW infants, 7-10% weight loss seems to be adequate taking into account their higher body water content and the adverse complications associated with fluid overload 1.
• Electrolytes (Na, Cl, and K) should be supplied starting during phase I/contraction of ECF compartment/initial loss of body weight 1.
• Cl intake should be slightly lower than the sum of Na and K intakes to avoid excessive Cl intakes and risk of iatrogenic metabolic acidosis 1.

From the Research

Normal Weight Loss Range for Newborns

• The normal weight loss range for newborns in the first week of life can vary, with studies showing a mean weight loss of 4.9% to 7.68% of birth weight 2, 3.
• Some studies have reported a mean absolute weight loss of 228g ± 83g, and a mean percent weight loss of 6.7% ± 2.2% 4.
• Weight loss of more than 7% appears to be a normal phenomenon among full-term newborns, with some studies showing that more than half of healthy, full-term newborns lost more than 7% of their birth weight 5, 3.

Supplementation Consideration

• The decision to consider supplementation should be individualized and based on various factors that influence the percentage of weight loss in newborns, rather than solely on the percentage of weight loss 6.
• Formula supplementation may be considered when weight loss exceeds 10% of birth weight, but this may not always be necessary 6, 4.
• Exclusive breastfeeding rates may be lower in newborns who lose more than 7% of their birth weight, suggesting that supplementation may be considered in these cases 5, 3.
• However, breastfeeding, compared to formula feeding, may not be a risk factor for greater early neonatal weight loss, at least in contexts where weight is routinely monitored and breastfeeding is supported 4.