Growing Premature Babies Slow and Steady – by Kath Megaw

Babies born at less than 37 weeks gestation (premature) have different nutritional needs than babies born at full term (after 38 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 to 37 weeks often have problems feeding from a bottle or a breast. This is because they are not yet mature enough to coordinate sucking, breathing, and swallowing.

Other illness can also interfere with a new-born’s ability to feed by mouth. Some of these include:

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

New-born babies who 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, especially for very premature babies. 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 after 34 to 37 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. However, they may also have problems maintaining proper suction at the breast to get enough milk to meet their needs. For this reason, even older premature babies may need gavage feedings in some cases.


Preterm babies have a harder time maintaining the proper water balance in their bodies. These babies can become dehydrated or over-hydrated. This is especially true for very premature infants.

  • Premature infants 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 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

  • Many NICUs will give donor milk from a milk bank to high-risk babies who cannot get enough milk from their own mother.
  • Special preterm formulas can also be used. These formulas have more added calcium 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 some 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 as well as iron and vitamin D supplements. Some babies will need more supplementation than others. This may include babies who are not able to take in a sufficient volume of milk through breastfeeding to get the calories they need to grow well



Weight gain is monitored closely for all babies. Premature babies with slow growth appear to have more delayed development in research studies.

  • In the NICU, babies are weighed every day.
  • It is 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 and gestational age. Sicker babies may need to be given more calories in order to grow at the desired rate.

  • It might be as little as 5 grams a day for a tiny baby at 24 weeks, or 20 to 30 grams a day for a larger baby at 33 or more weeks.
  • In general, a baby should gain about 15 grams per kilogram per day. It is the average rate at which a foetus grows during the third trimester.

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 on how much the baby must weigh before going home, but this is becoming less common. In general, babies are at least 1,8kg before they go into an incubator!


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