*Article* **Identification of Growth Patterns in Low Birth Weight Infants from Birth to 5 Years of Age: Nationwide Korean Cohort Study**

**So Jin Yoon, Joohee Lim, Jung Ho Han, Jeong Eun Shin, Soon Min Lee \*, Ho Seon Eun, Min Soo Park and Kook In Park**

> Department of Pediatrics, Yonsei University College of Medicine, Seoul 06273, Korea; sojinyoon@yuhs.ac (S.J.Y.); imagine513@yuhs.ac (J.L.); feagd@yuhs.ac (J.H.H.); golden-week@yuhs.ac (J.E.S.); hseun@yuhs.ac (H.S.E.); minspark@yuhs.ac (M.S.P.); kipark@yuhs.ac (K.I.P.)

**\*** Correspondence: smlee@yuhs.ac; Tel.: +82-2-2019-3350

**Abstract:** This study aimed to investigate the nationwide growth pattern of infants in Korea according to the birth-weight group and to analyze the effect of growth on development. A total of 430,541 infants, born in 2013 and who received the infant health check-up regularly from 6 months to 60 months of age, were included. The weight, height, head circumferences percentiles, and neurodevelopment using screening tests results were compared among the birth-weight groups. Using longitudinal analysis, the study found a significant difference in height, weight, and head circumference, respectively, according to age at health check-up, birth weight group, and combination of age and birth weight (*p* < 0.001). The growth parameters at 60 months of age showed a significant correlation with those at 6 months of age especially in extremely low birth weight infants. The incidence of suspected developmental delay was significantly higher in infants with growth below the 10th percentiles than in those with growth above the 10th percentiles. Among 4571 (1.6%) infants with suspected developmental delay results at 60 months of age, birth weight, sex, and poor growth parameters were confirmed as associated factors. This nationwide Korean study shows that poor growth and neurodevelopment outcomes persisted among low-birth-weight infants at 60 months of age. Our findings provide guidance for developing a nationwide follow-up program for infants with perinatal risk factors in Korea.

**Keywords:** developmental delay; child health; birth weight; growth measurement
