The Xi’an longitudinal mother–child cohort study: design, study population and methods

The large-scale Xi’an longitudinal mother–child cohort study has started to enroll pregnant women who attended Northwest Women’s and Children’s Hospital (NWCH) for antenatal care in early pregnancy (less than 20 weeks’ gestation) from January 2013 and the enrollment will be ended in January 2023. We aimed to investigate the role of external factors (i.e., diet and environment) and internal (i.e., biological, genetic and epigenetic) on the short- and long-term outcomes of mothers and children up to at least 12 years. Mothers completed all routine prenatal care during pregnancy and four times of follow-up at 42 days, 3, 6 and 12 years after delivery, respectively. For children, birth information were obtained from routine medical records and the follow-up information were obtained from child health care clinics of NWCH at age 42 days, 6, 12 and 24 months, then by interviewing mothers every two years until 12 years old. A range of data (including biological, demographic, birth outcomes/birth defects and nutritional factors from both maternal and off-spring) were collected by both interviews and laboratory tests. By June 30th 2019, a total of 114,946 mothers and 124,454 live births had been recruited.