Physiological Norm

All newborn babies go through what is called physiological weight loss—a normal process during the first few days of life. Most early weight loss happens because of fluid retention during labor and the passage of meconium (early stools) after birth.

According to the National Institutes of Health, infants lose the most weight on days 2 and 3, with an average loss of 5–7% from birth. Pediatricians become concerned when weight loss reaches 10% or more, as this may be a sign of feeding difficulties or potential dehydration that needs attention.

Weight Loss and Gain Expectations

In most cases, newborn babies regain their birth weight by days 10–14, though some may take longer, especially if born by cesarean section. The American Academy of Pediatrics (AAP) notes that the timeline can vary based on several factors, including the length of the pregnancy and whether the baby is exclusively breastfed or receives infant formula.

The Academy of Breastfeeding Medicine recommends that infants begin gaining steadily around days 4–6, which usually corresponds to when colostrum transitions to larger volumes of more mature breast milk. If a baby remains at a 7% weight loss or greater by day 6, or has not started gaining by the end of the first week, it’s important to have feeding evaluated by a pediatrician or lactation consultant.

Cesarean Section and Weight Loss

Babies born via cesarean section often have more fluid retention, which can make their birth weight loss appear greater in the first few days. AAP studies show that breastfed babies delivered by cesarean are twice as likely to experience ≥10% weight loss compared to those born vaginally.

It’s also common for cesarean-born infants to take longer to regain their birth weight. These newborn babies should be monitored closely—looking not only at ounces gained on the scale, but also at other indicators like alertness, feeding frequency, and diaper output.

Discharge Home

After going home, it’s recommended that babies see their healthcare provider between days 3–5 to check weight gain, feeding, and hydration. During the first month, parents can track progress by watching for these signs that their baby is getting enough nutrition:

  • Feeding 8–12 times in 24 hours, going no longer than one 4–5 hour stretch between feedings at night

  • Appearing satisfied after most feedings, except during short growth spurts when cluster feeding is normal

  • Producing at least 6 wet diapers per day by days 4–5

  • Having at least 3 yellow, seedy stools per day by days 4–5

Tracking both wet and dirty diapers is one of the best ways to monitor hydration and nutrition between check-ups. If breastfeeding is painful or your baby seems persistently unsatisfied, it may indicate a latch issue or poor milk transfer. A lactation consultant can help you assess and improve feeding, ensuring your baby is getting enough nutrition to thrive.

Watching the Signs That Feedings Are Going Well

Every baby’s growth story unfolds a little differently. What matters most is being attentive to their hunger cues, noticing how satisfied they are after feedings, and tracking diaper output in the early days. Stay connected with your baby’s pediatrician for regular check-ups, and reach out for breastfeeding support whenever you need it. With a little time and the right guidance, you’ll gain confidence knowing your baby is getting exactly what they need to grow and thrive.

Disclaimer: Our classes and accompanying materials are intended for general education purposes and should not replace medical advice. For personalized recommendations, please consult your healthcare provider and/or lactation consultant.