GROWTH VELOCITY IN VERY LOW BIRTH WEIGHT INFANTS. ARE THE REFERENCE GROWTH CHARTS APPROPRIATE?

Abstract

Growth of very low birth weight infants (VLBWI) is usually assesed by Standard Reference Curves (SRC). These chars are composed by prenatal growth curves up to term (cross sectional studies) followed by post natal longitudinal growth charts of fullterm healthy babies. Our purpose was to compare the growth velocity of SRC with the lenght, weight and head circumference growth velocity of a population of 35 VLBWI with low neonatal morbidity and adequate weight for gestational age, who were followed up for one year of corrected age. Birth weight of this population was (x̄ ± SD): 1290 ± 150, lenght: 38.3 ± 2.8, head circumference: 26.3 ± 1.3 and gestational age: 30 ± 1.3 weeks. The accelerated growth period of the three parameters showed a quadratic regression (parabola), with its acme retarded 4 weeks compared to SRC for weight and 5 weeks for head circumference and body lenght, its magnitude being significantly greater (p < 0.01) in the SRC (for weight and lenght) than in the VLBWI (350g ± 80 vs 270 ± 90 and 1.3 ± 0.2 vs 1.02 ± 0.1). Total accumulated growth at one year was similar in both curves.Increased growth velocity in VLBWI lasted until six months of corrected age and not up to full term only as in SRC. Our results suggest that for clinical assessement of rapid growth period in premature infants, SRC do not adequately reflect changes in growth velocity during this critical period.