What New Parents Should Know About Newborn Weight Gain

Learn What's Normal for Newborns

Mother holding sleeping baby
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Of all the numbers associated with a baby's birth—14 hours of labor, 10 fingers and toes, a solid APGAR score of 8—her weight can feel like one of the most important. After all, nothing says healthy and hearty like a respectable number on the scale. So when an infant loses a few ounces, it can be a bit scary and lead to all sorts of speculation: Isn't she eating enough? Is she ill?

In fact, it's rarely a cause for concern when a newborn's weight wafts downward after she's born.

Here's why, and how to tell if a baby's weight loss is normal and when it's not.

Why Newborns Lose Weight

Most babies shed a few ounces during the first week of life. For example, a newborn who tips the scale at, say, exactly 7 pounds at birth may leave the hospital a day or two later weighing 6 pounds, 6 ounces. The reason is simple: Babies are born with excess fluid, which they begin to lose right away. Because of this, and also some breakdown of tissue, the average infant will lose between 7 percent to 10 percent of her body weight during her first several days of life.

Most infants plump back up to their birth weight within seven to 10 days. After that, a new baby will begin putting on about an ounce a day. At that rate, by the time she's 4 to 6 months old, she'll weigh double her birth weight. The bottom line, then, is that as long as a newborn's weight begins to climb at a steady rate after that initial drop, she's right on track.

When to Worry About Your Baby's Weight 

If a baby over a month old loses weight or doesn't seem to be gaining at a healthy rate, it's often because she isn't eating enough. Here are some things to consider if you and your pediatrician are worried your newborn isn't getting the amount of breastmilk or formula she needs in order to grow at a healthy pace:

  • How often she eats. Breastfed babies typically will want to nurse at least eight times every 24 hours. Formula-fed babies will take a bottle less often: every three to four hours. 
  • How much she eats. It's easy to measure the amount of formula a baby takes from a bottle—usually 3 to 4 ounces at a time. Some ways to tell if a breastfeeding baby is taking in enough: She nurses for at least 10 minutes, you can hear her swallowing, and she seems satisfied when she finishes. If your baby turns up her nose at the nipple or is fussy after nursing no matter how long she's at the breast, a lactation consultant may be able to help.
  • How many wet diapers she has. Until her mother's milk comes in, a baby who's being exclusively breastfed may have only one or two wet diapers a day. By 3 to 5 days old, all babies should have six wet diapers a day, and six to eight after that.
  • How many poopy diapers she has. By 3 to 4 days old babies settle into a norm of several of these per day. Keep in mind breastfed infants typically have more bowel movements than those getting formula.

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