[1] Sichuan Univ, West China Univ Hosp 2, Natl Ctr Birth Defect Monitoring, Dept Obstet, Chengdu 610041, Sichuan, Peoples R China
[2] Sichuan Univ, Key Lab Birth Defects & Related Dis Women & Child, Minist Educ, Sec 3,17 South Renmin Rd, Chengdu 610041, Sichuan, Peoples R China
[3] Sichuan Univ, West China Sch Publ Hlth, Chengdu, Sichuan, Peoples R China
[4] Southern Med Univ, Shenzhen Matern & Child Healthcare Hosp, Dept Ultrasound, Shenzhen, Guangdong, Peoples R China
[5] Hubei Matern & Child Healthcare Hosp, Dept Ultrasound, Wuhan, Hubei, Peoples R China
[6] Sichuan Matern & Child Healthcare Hosp, Dept Ultrasound, Chengdu, Sichuan, Peoples R China