Association of low birth weight with thinness and severe obesity in children aged 3-12 years: a large-scale population-based cross-sectional study in Shanghai, China.

Objectives Low birth weight (BW) is a general symbol of inadequate intrauterine conditions that elicit abnormal fetal growth and development. The aim of current study is to investigate the relationship between low BW and thinness or severe obesity during maturation. Design A large-scale cross-sectional population-based survey. Setting 134 kindergartens and 70 elementary schools. Participants 70 284 Chinese children aged 3-12 years. Outcome measures International Obesity Task Force body mass index (BMI) cut-offs were used to define grade 1, grade 2 and grade 3 thinness, overweight, obesity and severe obesity. Multinomial logistic regression was used to estimate the association between BW and BMI category. Results A total of 70 284 children participated in the survey. The percentage of grade 1 thinness and severe obesity in children with low BW is significantly higher than that in children with normal BW (p<0.05). Low BW was associated with an increased risk of grade 1 thinness (OR 1.56, 95% CI 1.38 to 1.75), grade 2 thinness (OR 1.34, 95% CI 1.10 to 1.64), grade 3 thinness (OR 1.99, 95% CI 1.63 to 2.42) and severe obesity (OR 1.27, 95% CI 1.03 to 1.55) but was not associated with obesity (OR 0.85, 95% CI 0.67 to 1.06). Conclusion There is a positive association between low BW and thinness or severe obesity risk.