Premature Birth: Baby's Weight Gain And Growth Chart

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Some women deliver their babies preterm (before the 37th week of pregnancy) due to various reasons. A significant concern of preterm birth is the low birth weight of the babies.

The American Academy of Pediatrics (AAP) opines that “development is not a race, and babies develop at their own pace” (1). Therefore babies, even those born premature, will gradually reach their developmental milestones, including that of weight, if optimal conditions are provided.

In this post, MomJunction guides you through the topic of premature baby weight gain and growth while providing vital information through a premature baby growth chart.

Understanding The Weight Of Premature Babies

The average weight of a newborn is seven pounds (3.17 kilograms). But the average weight of a preterm infant is about five pounds (2.26 kilograms) or less. The exact weight depends on how early the baby is delivered, with infants born after 28 weeks of pregnancy weighing 2.3 pounds (one kilogram) (2).

There is a difference in premature babies with low birth weight, compared to babies who suffered intra uterine growth retardation, so called “Small for gestational age” babies.

Weight, Height, And Head Circumference Growth In Premature Babies

The weight, height, and head circumference of a premature infant will vary depending on the gestational week of their birth and their overall health at birth. The following are some key points about the weight, height, and head circumference of premature babies:

Note that these are the average figures while the actual figures may differ from one baby to another.

  • Premature infants are put in the neonatal intensive care unit (NICU) and ideally start gaining weight within a few days after birth.
  • The weight gained can significantly differ among babies. A baby with a gestational age of 24 weeks (born after the 24th week of pregnancy) may attain five grams per day while those born at 33 weeks or later can put on as much as 30 grams per day (3).
  • The desirable weight gain in babies who are born with a birth weight of more than two kilograms is 20-30 grams per day (4).
  • The height of preterm babies increases by about 1.1 centimeters every week until the completion of the ideal gestational age, which is about 40 weeks.
  • The chronological age of the baby is the absolute age, which is the time from the birth of a premature baby to the present. This age is also called postnatal age.
  • A healthy premature infant is likely to show improvement first in the head circumference, followed by weight and height.

In the next section, we give you a detailed growth chart for premature infants.

[ Read: Guide To Track Your Premature Baby’s Development ]

Premature Baby Growth Chart

The Fenton growth chart for preterm infants is most commonly used for assessing the growth milestones of a premature baby. The Fenton chart was created in 2003 by Dr. Tannis Fenton, who revised it in 2013 to accommodate the new standards suggested by the World Health Organization (5).

In the next section, we list the approximate values for height, weight, and head circumferences for both preterm infant girls and boys. The value given is the 50th percentile, which is a median number (6).

Growth charts for premature infants

Weight, height, and head circumference of premature infant girls

Gestational Age In WeeksWeight In KilogramsHeight In CentimetersHead Circumference In Centimeters
240.6kg30cm21.1cm
260.8kg33cm23cm
281kg35.6cm25cm
301.3kg38.5cm27cm
321.7kg41.1cm29cm
342.1kg44cm30.5cm
362.6kg46.5cm32.1cm
383.1kg48.5cm33.5cm
403.4kg50.5cm34.9cm

Weight, height, and head circumference of premature infant boys

Gestational Age In WeeksWeight In KilogramsHeight In CentimetersHead Circumference In Centimeters
240.65kg31cm22cm
260.83kg34cm23.5cm
281.1kg36.5cm25.8cm
301.4kg39cm27.5cm
321.8kg42cm29.5cm
342.25kg44.9cm31cm
362.7kg47cm32.8cm
383.2kg49.5cm34cm
403.6kg51cm35cm

Source: Fenton Preterm Growth Chart Site, University of Calgary (7)

Not all babies develop the same way or at the same pace, as the growth at this stage depends on multiple factors. Doctors periodically assess a preterm baby in the NICU.

Note that the growth figures indicated by the doctor could be less or more than those mentioned in the chart. But as long as your doctor states that your baby is doing well, you can relax and look forward to taking your baby home from the NICU.

However, one thing you may still worry about is the baby’s nutrition as it can affect their weight significantly.

Nutrition For A Premature Baby

The doctors in the NICU will determine a premature baby’s feed after considering the gestational age and their overall health condition. Below are the sources of nourishment for a preterm infant:

  1. Intravenous fluids: Early preterm babies will not be able to breastfeed and will require an intravenous delivery of nutrients and other fluids. The IV solution will be a mix of all the compounds that the baby will need to thrive and grow stronger.
  1. Formula or breast milk through tube feeding: Once your baby’s digestive system is a bit strong, they can receive breast milk or formula directly into their stomach through a sterile tube that goes through their nose or mouth. This form of feeding is called nasogastric or orogastric tube feeding.

The doctor will determine the nature of the feed. If the mother is lactating sufficiently, then she can express breast milk, which would be then given to the baby through tube feeding. The quantity of breast milk or formula increases gradually in this method.

  1. Breastfeeding: If your baby is a late preterm infant (born between 34-37 weeks), then they may be able to breastfeed. Both the mother and baby will require some initial practice. But once the baby understands to latch to the nipple, you can breastfeed the premature baby just like you would a full-term baby.

If the baby has trouble latching, then you can provide expressed breast milk through a feeding bottle. In the case of preterm delivery, breastmilk has more protein, minerals, and fat that the baby can easily digest (8). Breastmilk will also reduce the risk of intestinal infection.

  1. Fortified formula: Breastmilk alone may not provide the nutrition that premature babies need to grow. They have a higher caloric requirement, usually around 120-kilocalories per kilogram of body weight per day (9). Fortified formula milk can provide the extra nutrition that preemies need, along with the right mix of vitamins and minerals for healthy growth. If required, the doctor may recommend this.

[ Read: Baby Growth Spurts ]

It could be painful to see your little one in an incubator. But know that this is a passing phase, and with the right kind of care and nutrition, the baby will gain weight and grow, to eventually catch up with the babies of their age. Once your baby is eating well, has normal body functions, and growing at the right pace, you can safely take the little one home.

References:

1. Preemie Milestones; American Academy of Pediatrics
2. Caring for a Premature Baby: What Parents Need to Know; American Academy of Pediatrics
3. Neonatal weight gain and nutrition; U.S. National Library of Medicine
4. NICU Family Information Packet; Agency for Healthcare Research and Quality
5. Fenton and Kim, A systematic review and meta-analysis to revise the Fenton growth chart for preterm infants; National Center for Biotechnology Information
6. Growth chart; U.S. National Library of Medicine
7. Fenton Preterm Growth Chart site; University of Calgary
8. Providing Breastmilk for Premature and Ill Newborns; American Academy of Pediatrics
9. Care of the Premature Infant: Part I. Monitoring Growth and Development; American Academy of Family Physicians

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