From the Guidelines
Normal newborn weight loss after birth should not exceed 10% of birth weight, according to the most recent guidelines. Typically, babies lose 5-10% of their birth weight during the first week of life, with breastfed babies potentially losing slightly more weight (up to 10%) compared to formula-fed babies (usually 5-7%) 1. This weight loss is expected and generally not concerning as long as it doesn't exceed 10% of birth weight. Most babies will regain their birth weight by 10-14 days of age. The initial weight loss occurs primarily due to fluid shifts, passage of meconium, and the small volumes of colostrum that newborns receive before mature milk comes in.
Key Points to Consider
- Weight loss exceeding 10% of birth weight, failure to regain birth weight by two weeks of age, or signs of dehydration (such as decreased urine output, dry mucous membranes, or lethargy) warrant medical evaluation 1.
- Parents should expect their newborn to have at least 6-8 wet diapers and 3-4 bowel movements daily by day 4-5, which indicates adequate feeding 1.
- Regular weight checks with a healthcare provider during the first two weeks are important to ensure the baby is gaining weight appropriately after the initial loss.
Guidelines and Recommendations
- The guidelines recommend a gradual increase of fluid intake in preterm and term neonates after birth, and electrolytes (Na, Cl, and K) should be supplied starting during phase I/contraction of ECF compartment/initial loss of body weight 1.
- It is essential to recognize that individual patient needs may deviate from generally recommended intakes depending on clinical circumstances such as fluid retention, dehydration, or excessive water losses 1.
From the Research
Normal Newborn Weight Loss
- Newborns can lose up to 10% of their birth weight during the first week of life and should regain it by two weeks of age, although this statement is based on outdated studies from the 1960s 2.
- A study found that the mean percent weight loss in healthy term infants was 6.7% ± 2.2%, with 6% of infants experiencing weight loss ≥ 10% and 0.3% experiencing weight loss > 12% 3.
- Factors such as cesarean section, hot season, any formula feeding, and jaundice not requiring phototherapy were independently associated with neonatal weight loss ≥ 8% 3.
- 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 3.
- Using 24-hour weight as a reference for weight loss calculation can reduce supplementation and promote exclusive breastfeeding in infants born by cesarean section 4.
Weight Loss and Breastfeeding
- Exclusively breastfed infants can experience weight loss, and the amount and timing of initial weight loss can vary 5.
- Intrapartum intravenous fluids may cause excessive weight loss in some newborn infants 5.
- Early limited-volume supplementation with donor human milk is unlikely to have a significant favorable impact on breastfeeding outcomes for newborns with ≥4.5% weight loss in the first 36 hours 6.
- Routine use of 24-hour weight as the reference for newborn weight loss calculation can reduce supplementation without increasing untoward effects during the hospital stay 4.