How Should the Preterm Infant Grow?

Abstract

Growth of the preterm infant remains an area of controversy. It is clear that the gold standard for weight gain in the preterm infant is to achieve the rate gain of the fetus at the same postconceptional age. This goal is not always easy to achieve, though at the time of discharge most preterm infants are at least growing parallel to the appropriate intrauterine growth curve. This report is an update of the topic previously reviewed for this journal. New intrauterine growth curves including BMI are now available for preterm infants. Extrauterine growth curves (post-natal) are available for BMI as well, but these types of curves for weight, length, and head circumference are not current or are under development. Body composition data for preterm infants is emerging but still limited to measurements at birth and corrected term age. The present recommendations for dietary intake do not allow for the necessary “catch-up” growth after the period of inadequate nutrition of preterm infants in the early weeks of life. Assessment of growth in the NICU should include accurate measurements of weight, length, and head circumference. Growth velocity should also be calculated, though there is no standardized method for this determination. Anthropometric measurements should be assessed using one of the presently available newer intrauterine growth curves. There are updated intrauterine growth curves available to assess the growth of the preterm infant. The need for catch-up growth and availability of appropriate extrauterine growth curves remain a challenge. Though there have been concerns about metabolic programming and adverse outcomes of rapid growth in preterm infants, evidence supporting these observations is weak with perhaps the exception of the preterm infant who is born small for gestational age. On the other hand, it is clear that adequate head growth is associated with improved neurodevelopmental outcome. This paper ends with a suggested individualized, overall, practical growth strategy for preterm infants in the NICU.