Child growth trajectory of discordant twin up to seven years of age

초록

Objectives Birthweight discordance, defined as a difference in the birthweights of twins, is a well-documented phenomenon in twin pregnancies and occurs in 15% to 30% of twin pregnancies depending on the chronicity, degree of discordance and the threshold. It is not clear whether catch-up growth exists within a set of discordant twins, although twins achieve the normal weight of singletons during infancy and up to adolescence. Therefore, the aim of this study is to evaluate the longitudinal patterns of growth in discordant twins. Methods This study was conducted by merging the Korean National Health Insurance (KNHI) claims database and a National Health Screening Program for Infants and Children database. Using the KNHI claims database, we identified all women who delivered twins between January 1, 2007, and December 31, 2010. Only discordant twins were included for analysis. The weight difference was calculated as “(larger twin weight−smaller twin weight) / larger twin weight×100”. The birthweight discordance and weight at age point discordance were defined as a weight difference of 20% or more at birth and at each age point. The linear spline mixed-effect model (LSMM) was selected, based on the differences between the negative of twice the log-likelihood (-2LogL) among several models with different random-effect terms. An alternative LSMM with a subject-specific random intercept and repeated time of trajectories was also applied to the weight discordance measure of each twin. Results A total of 3,408 twins and 1,704 mothers were included in this study. The mean of birthweight discordance was 28.68%. The gap in weight between the small twins and their large siblings significantly closed to 10% at 1 year of age and then remained at about 10% until 8 years of age. Conclusions Small twin in discordant twins showed catch-up growth in the first 12 months of life compared to their large siblings but after 1 year of age, no differences in growth velocity were found. Further studies are needed to evaluate the long-term pattern of growth and its effect on health.