[1] Xi An Jiao Tong Univ, Affiliated Hosp 1, Dept Obstet & Gynecol, Xian, Shaanxi, Peoples R China
[2] McMaster Univ, Fac Hlth Sci, Hamilton, ON, Canada
[3] McMaster Univ, Div Maternal Fetal Med, Dept Obstet & Gynecol, Hamilton, ON, Canada
[4] McMaster Univ, Div Maternal Fetal Med, Dept Diagnost Imaging, Hamilton, ON, Canada
[5] McMaster Univ, Div Maternal Fetal Med, Dept Clin Epidemiol & Biostat, Hamilton, ON, Canada