Catch-up growth: Normal for premature babies

by Ellyn Satter, Registered Dietitian and Family Therapist

Catchup growth is a normal and natural process in infancy. Feed even your small and/or premature baby on demand, according to her hunger and fullness cues, and time feeding based on her sleeping and waking rhythms. You may be advised to do prescriptive overfeeding: To feed your baby on a schedule and be told how much to feed her. Such tactics will make both you and your baby feel bad about feeding and impair her ability to eat as much as she needs and grow in the way that is right for her. Prescriptive overfeeding is quite different from normal demand feeding and may impair your baby’s growth. She may resist eating so much that she grows poorly, or she may give in and gain weight too fast. 

Rapid early childhood weight gain

Currently, epidemiologists, based on analyses of large population-based databases, hypothesize that much, if not most, early childhood rapid weight gain is counterproductive.^1,2,3,4  They suggest that infants and children who show rapid early weight gain are predisposed later in life to develop obesity,⁴  type 2 diabetes, and cardiovascular disease.² These studies suffer from lack of information about feeding dynamics: Were their small subjects fed on demand or had prescriptive overfeeding been imposed on them. Since standard practice in most newborn intensive care nurseries is prescriptive overfeeding, it is likely epidemiologists are studying an iatrogenic – medically induced – condition, caused by abnormal weight acceleration secondary to prescriptive overfeeding. 

Catchup growth supports brain and nervous system development

Catchup growth supports positive neurodevelopmental outcome.¹ Compared with term-born peers, infants born preterm typically show slow growth in the early postnatal period, especially if they are sick. However, this slow start is followed by catchup growth over 2–3 years, and preterm babies achieve a slightly lower mean adult height.³ Infants whose medical condition has been stabilized can successfully be fed on demand, with care providers reading and responding to their feeding and sleeping cues.^5,6,7,8,9 Catchup growth that results from this child-driven feeding demonstrates canalization. That is, after a period of growth acceleration, the child’s growth settles on its constitutionally preferred channel, or percentile.¹⁰ Once it finds its trajectory, the child’s weight tracks reasonably consistently at his or her own preferred percentile,^11,12 whether being plotted against the CDC or WHO standards¹³ or monitored using z- scores. Such consistent growth represents normal growth for the individual child, even if it is below or above the percentile or z-score extremes generally defined as non-organic failure to thrive¹⁴ or obesity.¹⁵

Height restoration comes before weight

To do no harm. we must feed each preterm, tiny, fragile, and medically stabilized infant in a child-driven fashion and allow that child to grow in the way that is right for her.

Restoring body tissue appears to take precedence over restoring linear growth. Children who show low weight for height, but not low height for age, gain weight at a rate up to 20 times usual. In contrast, children with both low W/H and H/A tend to grow at about 2-3 times the usual rate in both weight and height until those growth values level off and channelize.^12,16,17 Complete catchup growth can occur even with severe growth retardation, provided epiphyseal fusion has not occurred: that is, the growth plates are still active. Pubertal development is often delayed for as long as two years in previously malnourished children and can allow for complete catchup in linear growth.¹⁸

Distinguish between normal catchup growth and force-fed weight acceleration

When children are fed according to sDOR, they achieve catchup growth in accordance with their own genetic endowment. Such feeding emphasizes the quality of the feeding relationship, supporting infant homeostasis, with feeding guided by the child’s sleeping and feeding cues. Because the child regulates based on calorie intake rather than volume ingested, catchup growth proceeds in this smooth and internally predicated fashion even when the child is being given calorically concentrated feeds.  In contrast, abnormal weight acceleration secondary to prescriptive feeding shows abrupt shifts from previous patterns. With prescriptive feeding, the child’s hunger and satiety cues are overwhelmed and he is induced to eat calculated amounts, or those cues are bypassed altogether by delivering those calculated amounts of formula by gavage or gastrostomy tubes. 

Most newborn intensive care nurseries feed prescriptively

Prescriptive feeding is part of usual NICU practice based on long tradition rather than evidence⁶ This practice is based on the assumption that the preterm or fragile infant is not able to take an active role in feeding and, therefore, must be stimulated to take in a prescribed amount. The Supporting Oral Feeding in Fragile Infants (SOFFI) method⁶ offers a child-driven alternative to prescriptive NICU feeding.

Early rapid infant weight gain is normal and positive

We are left with a new working hypothesis that makes distinctions based on quality of feeding, and it is this: Infants who are fed according to sDOR and allowed to achieve normal catchup growth are healthier, throughout life, and more inclined to achieve stable body weight than infants who achieve abnormal weight acceleration based on prescriptive feeding.

Studies examining this hypothesis will be difficult, expensive, and likely uninteresting to the obesity-hysterical. Until those studies are done, however, we are left with doing no harm. That is, we must feed each preterm, tiny, fragile, and medically stabilized infant in a child driven fashion and allow that child to grow in the way that is right for him or her.