Infant Weight Loss After Birth

Due to a number of environmental and physiological factors, an infant's weight two to three days after birth is often significantly lower than her birth weight. This weight loss is usually normal and not a cause for concern.

Average Loss

The average baby loses between 5 percent and 7 percent of his birth weight within the first 72 hours. Any loss under 10 percent is considered normal. Losses above this amount require professional evaluation of the infant's eating habits.

Regaining Weight

The majority of infants, whether breast-fed or formula-fed, regain the lost weight within three weeks of birth. If your baby does not regain the weight, your pediatrician may suggest more frequent weight checks. If you're breast-feeding, she may suggest formula supplements and an evaluation by a lactation consultant.

Excess Fluids

The loss of excess fluids is one of the most common reasons for infant weight loss after birth. This is especially true if you received IV fluids during your labor.

Meconium

The passage of the first bowel movement--a black, tarry substance known as meconium--causes a decrease in weight shortly after birth.

Breast-feeding

Because your milk does not "come in,"--that is, switch from the sweet pre-milk known as colostrum to true breast milk--until several days after birth, breast-fed babies may lose slightly more weight after birth. However, on average, these babies gain the weight back as well as their formula-fed counterparts.