Cohort profile: the Shenzhen Birth Cohort (SZBC) study.

PURPOSE: The Shenzhen Birth Cohort (SZBC) is an ongoing prospective study established to investigate the impact of genetic, environmental and lifestyle factors on maternal health and child development in Shenzhen, a metropolis characterised by rapid economic development and a high density of young migrants. PARTICIPANTS: Since March 2018, pregnant women (≤19 weeks of gestation) have been recruited from Nanshan Maternity & Child Healthcare Hospital of Shenzhen. Follow-up assessments are conducted at up to 20 time points from early pregnancy through delivery and childhood (up to 7 years of age). Extensive health data were collected through standardised questionnaires, physical examinations and biological samples (eg, blood, urine, faeces). FINDINGS TO DATE: As of December 2025, 4208 pregnant women were enrolled, of whom 3962 completed baseline data collection and constituted the baseline cohort; 3150 deliveries had been recorded. Preliminary findings included the following: (1) Maternal lifestyles and adverse birth outcomes: poor sleep quality in early pregnancy was associated with higher risks of small-for-gestational-age (SGA). (2) Maternal health conditions and neurodevelopment: higher pre-pregnancy BMI was associated with developmental delays in offspring, particularly in boys. (3) Environmental exposures and neurodevelopment: prenatal exposure to greenness was associated with higher levels of motor development, whereas postnatal PM₂.₅ exposure (notably nitrate) was associated with increased risks of delayed motor and problem-solving development. FUTURE PLANS: Recruitment is planned to continue through 2028, with enrolled children undergoing regular follow-up through 7 years of age. The current phase of cohort follow-up is expected to be completed in 2035. Future studies will integrate electronic medical records and multi-omics data to examine the combined effects of early-life exposures and explore potential biological pathways related to maternal and child health.