Obstetrics Second ward;
Yan'an University Affiliated Hospital;
Yan'an Shaanxi 716000;
P. R. China;
Otolaryngology;
Yan'an University Affiliated Hospital;
Yan'an Shaanxi 716000;
P. R. China;
Gynecological Second ward;
Yan'an University Affiliated Hospital;
Yan'an Shaanxi 716000;
P. R. China;