Background China’s unprecedented internal migration has left 61 million rural children living apart from parents. This study investigates the associations between being left behind by parents and children’s nutritional status in terms of height and weight trajectories by age, testing the accumulation and critical period life course hypotheses.

Methods Data were drawn from five waves of the China Health and Nutrition Survey (CHNS). Multiple cohorts of children under 6 years old from 1997 to 2009 were examined (N = 2,555). Growth curve models investigated whether height and weight trajectories differ for children who were left behind at different stages of the life course: in early childhood (from ages 0 to 5 but not afterwards), in later childhood (from ages 6 to 17 only), and in both early and later childhood (from ages 0 to 5 and from ages 6 to 17), compared to their peers from intact households.

Results Boys who were left behind at different life stages of childhood differed in height growth and weight growth compared with boys from intact families, although no significant associations were found for girls. As boys grew into adolescence, those left behind in early childhood tended to have slower height growth and weight gain than their peers from intact households. There was a 2.8 cm difference in the predicted heights of boys who were left behind in early childhood compared to boys from intact households, by the age of 14. Similarly, the difference in weight between the two groups of boys was 5.3 kg by the age of 14.

Conclusion Being left behind during early childhood, as compared to not being left behind, could lead to slower growth rates of height and weight for boys. The life course approach adopted in this study suggests that early childhood is a critical period of children’s growth in later life, especially for boys who are left behind. The gender paradox in China, where sons are preferred, but being left behind appears to affect boys more than girls, needs further exploration.