Neonatal weight gain and nutrition

Feeding and growing is one of the most important tasks of small babies in the hospital.

It is important that premature babies receive the right nutrition so they reach a weight similar to that they would have gained if they were still inside the womb.


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

Premature babies will often stay in the neonatal intensive care unit, where they will be carefully monitored to make sure they are getting the right balance of fluids, minerals such as sodium and potassium (electrolytes), and nutrition until their bodies mature.

Incubators or special warmers help reduce excess calorie needs so babies don’t have to use as much energy to stay warm. Humidified (moistened) air helps maintain body temperature and avoid fluid loss.


Babies born before 34 weeks often can't feed from a bottle or breast because they have trouble coordinating sucking, breathing, and swallowing. Also, newborns with breathing problems, very low oxygen levels, gagging, circulatory problems, blood infection, or other illnesses might not be able to feed through a nipple (orally).

Neonates who are very small or sick may need to get nutrition and fluids through a vein (intravenously). As they get bigger and stronger, they can start to receive breast milk or formula through a small tube inserted through the nose or mouth into the stomach (gavage feeding).

The amount of milk or formula is increased very slowly to reduce the risk of getting 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 managing breastfeeding than bottle feeding at first, because the flow from a bottle is harder for them to control, causing them to choke or stop breathing. Sometimes it's easier for them to use a “slow flow” nipple for bottle feeding at first.


Preterm babies lose more water through the skin or respiratory tract than babies born at full term. Also, the kidneys in a premature baby have not grown enough to control water levels in the body. Such babies can become dehydrated or overhydrated. 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 recommended diet for human babies especially for those born early and at very low birth weight. Research suggests that breast milkprotects babies against infections and sudden infant death syndrome (SIDS) as well as NEC.

If it is not possible for the baby to have his or her own mother’s milk, some NICUs will give donor milk from a milk bank to very high-risk babies. 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. Once babies reach 34 - 36 weeks gestation, they can be switched to regular formula or a “transitional formula” for older preterm babies.

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 supplement contains the extra protein, calories, iron, calcium, and vitamins that premature babies need. Those who are fed formula may need to take added supplements of certain nutrients, including vitamins A, C, and D, and folic acid. Some infants who were born prematurely 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. For all babies, weight gain is monitored closely.


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 aren't released from the hospital until they are gaining weight steadily 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.

After each feeding, babies should seem satisfied. They should have up to 6-8 stools and at least 6 - 8 wet diapers each day. Watery or bloody stools or regular vomiting could signal a problem.

Alternative Names

Newborn nutrition; Nutritional needs -- premature infants


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

Update Date: 5/9/2012

Reviewed by: Kimberly G Lee, MD, MSc, IBCLC, Associate Professor of Pediatrics, Division of Neonatology, Medical University of South Carolina, Charleston, SC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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