The Jiaxing Birth Cohort (JBC) is the largest prospective cohort study to explore prenatal risk factors, early life feeding practice and growth pattern/ adiposity in Chinese children.Between 1999 and 2013, 338 413 mother-child pairs were recruited in Jiaxing area in south-east China.Children of the recruited women were followed up at 1-2, 3, 6, 9 and 12 months of age, and subsequently followed up every 6 months to 36 months of age (toddler stage), and every year to 6-7 years of age before they went to school (pre-school stage). Follow-up rate was 70.8% at the toddler stage and 68.9% at the pre-school stage up to June 2013.