Overview of the establishment of Shanghai twin birth cohort

ObjectiveTo establish the Shanghai twin birth cohort （STBC） and analyze the effects of genetic factors， shared environment， and non-shared environment interactions on birth health and growth and development of newborns.MethodsBased on the population-wide birth cohort in Shanghai， a comprehensive survey was conducted on the families with double and multiple babies born after January 1， 2015 to collect information on birth health， growth and development， and the family environment of the babies.ResultsBy December 31， 2021， a total of 7 195 pairs （14 405 cases） of twins were successfully included in the STBC survey. The average birth length of twins was 47.2 cm and average birth weight was 2 465.3 g. Heterozygous twins accounted for 69.05% and preterm babies accounted for 57.07%. The average age of the mothers of twins was 31.82 years， and the average age of the fathers was 33.87 years， with more than 80% of the parents having a college degree or above. 44.50% of the mothers used assisted reproductive technologi