Postnatal growth of preterm infants during the first two years of life: catch-up growth accompanied by risk of overweight

Abstract

Background: Early postanal growth of preterm infants has many effects on early and late health. However, evidence on growth pattern in Chinese preterm infant population during early life is insufficient. This study aims to describe the growth trajectory, catch-up growth, and risk of overweight of preterm infants during the first 2 years of life in a Chinese community population.

Methods: All preterm infants (n = 10,624) received routine childcare in one primary maternal and child healthcare network in 8 years were included. Body weight and length/height at corrected age (CA) 40 weeks, CA 3 months, 6 months, 9 months, 12 months, 18 months, and 24 months were extracted and converted to z-scores based on the World Health Organization (WHO) standards. According to the intrauterine growth status, infants were divided into small for gestational age (SGA), appropriate for gestational age (AGA), and large for gestational age (LGA) infants. Changes of z-score were used to describe the growth velocity. Generalized estimating equation (GEE) model was used to analyze growth trajectory trends over time.

Results: Body weight and length/height were overall above the WHO standards during the first 2 years of life. Z-score increased significantly by 0.08 (95% CI: 0.06-0.10) in weight and 0.07 (95% CI: 0.04-0.09) in length/height from CA 40 weeks to 3 months and then levelled off until CA 24 months after adjustment. Almost 90% of AGA and LGA infants achieved growth targets (≥25th percentile of WHO standards), and over 85% of SGA infants achieved catch-up growth (≥10th percentile of WHO standards) before CA 24 months. However, the risk of overweight appeared during this period, with the proportion of infants with the risk of overweight being at the peak at CA 3 months (25.6% of all preterm infants and 39.4% of LGA infants). Growth trajectories of SGA showed increasing trends, but those of LGA showed decreasing trends during the first 2 years.

Conclusions: Body weight and length/height of preterm infants are above the WHO standards in the Chinese community population during the first 2 years of life. Catch-up growth is accompanied by risk of overweight as early as CA 3 months. (349 words).

Keywords: Catch-up growth; Growth; Overweight; Preterm.

Fig. 1

Growth trajectories of preterm infants from CA 40 weeks to 24 months. a Growth trajectory of body weight in preterm infants and the mean level of the WHO standard. b Growth trajectory of length/height in preterm infants and the mean level of the WHO standards. CA, corrected age; WHO, World Health Organization

Fig. 2

Achieving target growth and risk of overweight from CA 40 weeks to 24 months in preterm infants. a The proportion of infants who achieved target growth or achieved catch-up growth. b The proportion of infants with risk of overweight. CA, corrected age; SGA, small for gestational age; AGA, appropriate for gestational age; LGA, large for gestational age

Fig. 3

Growth trajectories of LGA, AGA, and SGA preterm infants from CA 40 weeks to 24 months. a Growth of body weight in LGA, AGA, and SGA infants. b Growth of length/height in LGA, AGA, and SGA infants. CA, corrected age; SGA, small for gestational age; AGA, appropriate for gestational age; LGA, large for gestational age