Weight loss in newborns

Weight loss in newborns: When is it normal and when is it not?

The first weighing after birth, and then another a few days later, shows a lower number on the scale. For many parents this becomes the first serious reason for concern. However, physiological weight loss in the first days of life is an absolutely normal and expected process that every healthy baby goes through. Understanding this mechanism will help you avoid unnecessary worry.

Why do newborns lose weight?

Weight loss is related to the baby's adaptation to life outside the womb. It is not due to underfeeding, but is the result of eliminating excess fluid and the first bowel movements.

• Elimination of excess fluid. In the womb the baby's body was more "waterlogged." After birth the body begins to get rid of this excess fluid through urine and the skin.
• Passing meconium. Meconium is the first dark, sticky stool of the baby that accumulated in its intestine during pregnancy. Its passage also contributes to weight loss.
• Small amount of colostrum. In the first days after delivery your breasts produce a small but extremely nutritious and concentrated fluid — colostrum. Its volume (5-10 ml per feeding) is more than enough for the tiny stomach of a newborn, but its caloric content does not yet cover all energy needs.

Norms and “red flags”

Normally, a full‑term, healthy baby can lose up to 7‑10% of its birth weight. For example, if a baby is born weighing 3500 g, a loss of up to 350 g is completely acceptable. This process usually lasts 3‑4 days.

Later, with the arrival of mature milk (usually on day 3‑5), the baby's weight should stabilize and start to increase. By day 10‑14 of life the baby should have regained its birth weight. This is the main indicator that breastfeeding is properly established and the baby is receiving enough nutrition.

When should you be concerned?

• Weight loss exceeds 10%.
• The baby continues to lose weight after the 5th day of life.
• The baby has not regained birth weight by the 14th day.
• Signs of dehydration or lethargy are observed.

In such cases careful monitoring by a pediatrician and a lactation consultant is required to promptly identify and correct possible feeding difficulties.