The NPGSC cohort prospectively follows mothers and their babies since pregnancy. The mothers were recruited from public hospitals and community health care centres in Southwest China (Sichuan Province, Yunnan Province and Guizhou Province) during their first routine ultrasound examination between their ninth and eleventh gestational week. Approximately 48% of women came from urban areas, they were 26.3 years old on average at the time of the pregnancy, and more than half of them accepted education of university level. Follow up of babies was planned until age 3 at baseline, but would continue until young adulthood subject to funding.