2.1 Study population and design
The present study was based on the baseline study of the birth cohort in Jinan, the capital city of Shandong Province in China, from December 2018 to December 2019. Data were collected in 15 community vaccination clinics which were selected from 116 community vaccination clinics in the study area. Women who met the inclusion criteria were investigated when their newborns were filed for outpatient vaccination.
Eligibility criteria included: (1) the infant was delivered without congenital disease; (2) lived in Jinan during pregnancy; (3) does not have mental diseases or other diseases that affect normal communication. Only singleton live births were included.
A self-designed questionnaire for basic information of infants and mothers was used for a one-to-one face-to-face questionnaire survey. The information about infants includes birth outcomes, newborn birth weight, and so on, the maternal information including her general demographic characteristics, family economic conditions, last menstrual period and gestational age, physical exercise during pregnancy (including the frequency, time, and primary exercise patterns), and others included maternal tobacco exposure, work, and nutrition during pregnancy.
The study was approved by the Ethics Committee of Preventive Medicine of Shandong University (Approved number: 20170315), and all participants gave their informed consent.