IGF-I, Growth, and Body Composition in Preterm Infants up to Term Equivalent Age

Abstract

Context There are concerns that a higher fat mass in the early life of preterm infants is associated with adverse cardiometabolic outcomes in young adulthood. Objective To investigate the role of IGF-I and growth in determining body composition of preterm infants at term equivalent age. Methods An observational study was conducted from August 2015 to August 2018. From birth to term equivalent age, IGF-I levels were measured bi-weekly and growth was assessed weekly. At term equivalent age, body composition was assessed through air displacement plethysmography; 65 infants with a gestational age of 24 to 32 weeks were assessed at term equivalent age, of whom 58 completed body composition measurement. The main outcome measures were fat (free) mass (g) and fat (free) mass percentage at term equivalent age. Results In the first month of life, each 0.1 nmol/L per week increase in IGF-I was associated with a 465 g (SE 125 g) increase in fat free mass. A greater increase in weight SDS in the first month of life was associated with a higher fat free mass percentage (B 200.9; 95% CI, 12.1-389.6). A higher head circumference SDS was associated with more fat free mass (r = 0.46; 95% CI, 0.21-0.65). However, a greater increase in weight SDS up to term equivalent age was associated with a lower fat free mass percentage (B −55.7, SE 9.4). Conclusion These findings suggest that impaired growth in the first month of life is associated with a less favorable body composition at term equivalent age.

Preterm birth and metabolic implications on later life: A narrative review focused on body composition

“…Prematurity refers to a birth that occurs before 37 weeks of pregnancy (1). According to the gestational age (GA), PB is stratified into extremely preterm (GA < 28 weeks), very preterm (GA 28-32 weeks), moderate preterm (GA 32-34 weeks), and late preterm (GA 34-36 weeks), with increasing morbidity and mortality risk in lower GA (1).…”

“…There are few concepts and definitions that may overlap and should be clarified when approaching PB. Small for Gestational Age (SGA) refers to the birthweight below the 10th percentile of recommended sex-specific birth weight for the referenced GA (1).…”

“…Anthropometry consists of height, weight, head circumference, body circumferences, and skinfold thickness. It is considered an applicable, inexpensive, and non-invasive 10.3389/fnut.2022.978271 method to study measurements and proportions of the human body (1). Anthropometric indices that mathematically combine body weight and length, for example, body mass index (BMI), are often used to assess nutritional status as they are practical, reproducible, and easy to calculate (33).…”

“…Preterm birth (PB) may seriously affect postnatal growth and neurodevelopment and increase the risk of adverse outcomes from infancy to adulthood. Yearly, 15 million babies in the world are born before 37 weeks of gestation; in Europe, the estimated rate of PB ranges from 5 to 10% (1).…”

“…The enhanced importance of early life nutrition and optimization of growth in terms of body composition is mainly related to the advances in neonatal intensive care, which allow the survival of infants of lower gestational age. Indeed, rapid catch-up growth during infancy and childhood is related to an increased risk of developing non-communicable diseases, including cardiovascular diseases and metabolic syndrome in later life ( 2 ).…”