Newborn weight gain: what's normal & when to worry

Babies typically lose weight after birth, before they start to gain. A generally accepted rule of thumb is that a baby can be expected to lose about 3–7 percent of their birth weight during the first 5 days after birth. Parents should expect their baby to return to his or her birth weight by about day 10. 

Many babies double their birth weight by age 4 to 6 months and triple their birth weight by their first birthday. But babies who gain more slowly or more quickly may be perfectly healthy too. Your baby's doctor will monitor your baby's growth over time (weight, length, and head circumference) to ensure that they're getting all of the calories and nutrients they need. This is one reason why it's recommended babies have at least 6 doctor's visits during the first year.

Babies’ weight gain and loss doesn’t follow a pattern

It’s not clear how much weight exclusively breastfed babies lose and then gain in their first 14 days. A recent study of weight change in nearly 150,000 healthy babies found that it’s not uncommon for newborns to be below their birth weight even 21 days after delivery.

What are signs my baby is eating enough? 

Parents’ concern over weight is easy to understand given that it’s the only reliable indicator of growth. But if you know the signs that your baby is getting enough to eat, you don’t need an expensive in-home baby scale. A well-fed baby will… 

  • be active and alert 
  • be satisfied after breastfeeding 
  • breastfeed at least 8–12 times during each 24-hour period 
  • by day 3, have three or more poops a day
  • by day 5, have yellow poop
  • by day 5, have clear or pale yellow pee and six or more wet diapers a day

After 4 weeks of age, some babies continue to poop after every feeding, while others poop only once every other day, or once every 3–5 days. (Click here for more scoop on poop.) 

As long as you see these indicators of good health, there’s generally no reason to worry about having your baby’s weight measured between well-child visits.

What if my baby suddenly stops gaining weight? 

As long as your baby is reaching her developmental targets and isn’t losing weight, there’s no need to worry about a pause in weight gain. Children who fail to gain enough weight in the first 9 months will usually catch up over time. So parents seldom need to increase their child’s calories (by supplementing with donor milk or artificial infant formula). Consuming too many calories in infancy can actually lead to weight problems later in life. 

But if your baby loses more than 7 percent of their birth weight or gains weight slowly in the early days and weeks following their birth, your baby’s health care provider may ask you to bring them in for weight checks. A review of your breastfeeding routine and periodic weight checks will ensure that they're getting enough to eat and that there are no underlying health issues.

Does weight really matter? 

Weight is a measure of nutrition. When babies get too little food, too much food, or the wrong type of food, they can become malnourished. Today, experts agree that a brief period of underfeeding (days versus weeks or months) is unlikely to cause permanent damage. It can, however, have serious short-term consequences. Timing seems to be the key factor, since even a brief period of underfeeding in the first days after birth can lead to hyperbilirubinemia (jaundice) and hypoglycemia (low blood sugar). And if you’re concerned about your baby’s growth or feeding, contact their pediatrician.

Last updated February 12, 2021

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