BMI indicates body mass index; HBcAb, hepatitis B core antibody; HBeAb, hepatitis B envelop antibody; HBeAg, hepatitis B envelop antigen; HBsAb, hepatitis B surface antibody; HBsAg, hepatitis B surface antigen; HBV, hepatitis B virus; LMP, last menstrual period; NFPCP, National Free Preconception Checkup Project.