Assessment of growth pattern of preterm infants up to a corrected age of 24 months.

Objectives: To assess the growth of preterm infants up to a corrected age of 24 months, and to understand the growth trend and pattern of preterm infants.

Methods: A preterm infant follow-up database was established based on the Internet Plus follow-up system. A total of 3 188 preterm infants who were born from April 2018 to April 2021 were enrolled. Their length, weight, and head circumference were recorded at birth and at the corrected ages of 1, 3, 6, 12, 18, and 24 months. The preterm infants were grouped by perinatal factors. The growth curves of these infants were plotted and compared with the International Fetal and Newborn Growth Consortium for the 21st Century (INTERGROWTH-21st) standard and World Health Organization (WHO) standard.

Results: The weight, length, and head circumference curves of each group of preterm infants grouped by various perinatal factors all rose rapidly within the corrected age of 6 months, but the growth rate slowed down after the corrected age of 6 months. Based on the actual age for the groups of preterm infants with different gestational ages (<28 weeks, 28-31 weeks, 32-33 weeks, and 34-36 weeks), the length curve gradually coincided with the WHO curve after the actual age of 9 months (=0.082), while for the preterm infants with a gestational age of <32 weeks, the weight and head circumference curves were significantly lower than the WHO curves (<0.001). Based on the corrected age, the physical growth curve of preterm infants with different gestational ages (<28 weeks, 28-31 weeks, 32-33 weeks, and 34-36 weeks) basically coincided with each other (>0.05). For the infants with extremely low birth weight and the small-for-gestational-age infants, the length, weight, and head circumference curves were significantly lower than those of the INTERGROWTH-21st standard and the WHO standard (<0.05).

Conclusions: The physical growth rate of preterm infants is faster within the corrected age of 6 months, and the growth rate slows down after the corrected age of 6 months. Preterm infants with a smaller gestational age need longer time to catch up in weight and head circumference. More attention should be paid to the physical growth of extremely preterm infants, extremely low birth weight infants, and small-for-gestational-age infants.