Neonatal weight gain and nutrition


Premature babies need to receive good nutrition so they reach a weight close what they would have gained if they were still inside the womb.

Alternative Names

Newborn nutrition; Nutritional needs - premature infants


Babies born less than 37 weeks in the womb (premature) have different nutritional needs than babies born at full term (38 to 42 weeks).

Premature babies will often stay in the neonatal intensive care unit. There they are watched closely to make sure they are getting the right balance of fluids and nutrition.

Incubators or special warmers help babies maintain their body temperature. This reduces the energy the babies have to use to stay warm. Moist air is also used to help them maintain body temperature and avoid fluid loss.


Babies born before 34 weeks often have problems feeding from a bottle or a breast. This is because they have a hard time coordinating sucking, breathing, and swallowing.

Other illness can also interfere with a newborn’s ability to feed through a nipple. Some of these include:

  • Breathing problems
  • Low oxygen levels
  • Circulation problems
  • Blood infection

Newborn babies that are very small or sick may need to get nutrition and fluids through a vein (IV).

As they get stronger, they can start to get milk or formula through a tube that goes into the stomach through the nose or mouth. This is called gavage feeding. The amount of milk or formula is increased very slowly. This reduces the risk of an intestinal infection called necrotizing enterocolitis (NEC). Babies who are fed human milk are less likely to get NEC.

Babies who are less premature (born at or after 34 weeks gestation) often can be fed from a bottle or the mother's breast. Premature babies may have an easier time with breastfeeding than bottle feeding at first. This is because the flow from a bottle is harder for them to control and they can choke or stop breathing.


Preterm babies have a harder time maintaining the proper water balance in their bodies. These babies can become dehydrated or overhydrated.

  • They may lose more water through the skin or respiratory tract than babies born at full term.
  • The kidneys in a premature baby have not grown enough to control water levels in the body.
  • The NICU team keeps track of how much premature babies urinate (by weighing their diapers) to make sure that their fluid intake and urine output are balanced.
  • Blood tests are also done to monitor electrolyte levels.

Human milk from the baby’s own mother is the best for babies born early and at very low birth weight.

  • Breast milk can protect babies against infections and sudden infant death syndrome (SIDS) as well as NEC.
  • Some NICUs will give donor milk from a milk bank to very high-risk babies who are not able to have milk from their own mother.
  • Special preterm formulas can also be used. These formulas have a higher amount of fat and protein to meet the special growth needs of premature babies.
  • Older preterm babies (34 to 36 weeks gestation) may be switched to regular formula or a transitional formula.

Premature babies have not been in the womb long enough to store up the nutrients they need and must usually take supplements.

  • Babies who are given breast milk may need a supplement called human milk fortifier mixed into their feedings. This gives them extra protein, calories, iron, calcium, and vitamins.
  • Babies fed formula may need to take supplements of certain nutrients, including vitamins A, C, and D, and folic acid.
  • Some infants will need to continue taking nutritional supplements after they leave the hospital. For breastfeeding infants, this may mean a bottle or two of fortified breast milk per day. Some babies will need more supplementation than others in order to get enough calories to grow well. After each feeding, babies should seem satisfied. They should have up to 6 to 8 stools and at least 6 to 8 wet diapers each day. Watery or bloody stools or regular vomiting could signal a problem.


Weight gain is monitored closely for all babies.

  • In the NICU, babies are weighed every day.
  • It's normal for babies to lose weight in the first few days of life. Most of this loss is water weight.
  • Most premature infants should start gaining weight within a few days of birth.

The desired weight gain depends on the baby’s size, gestational age, and health.

  • It might be as little as 5 grams a day for a tiny baby at 24 weeks, or 20 grams a day for a larger baby at 33 weeks.
  • In any case, a baby should gain about a quarter of an ounce each day for every pound he or she weighs. (This is equal to 15 grams per kilogram per day).

Premature babies do not leave the hospital until they are gaining weight steadily and in an open crib rather than an incubator. Some hospitals have a rule how much the baby must weigh before going home. In general, babies are at least 4 pounds before they are ready to come out of the incubator.


Poindexter B, Denne S. Nutrition and metabolism in the high-risk neonate. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin’s Neonatal-Perinatal Medicine. 9th ed. St. Louis, Mo: Mosby Elsevier; 2010:chap 35.

American Academy of Pediatrics. Nutritional needs of the preterm infant. Pediatric Nutrition Handbook. Elk Grove Village, Il; AAP; 2009, pages 79-104.

This page was last updated on: 1/29/2019 3:21:13 PM

© 2020 Nicklaus Children's Hospital. All Rights Reserved.