Inclusion Criteria:  Pregnant women with 6-13(+6 days) gestational weeks Resided in Beijing in the past year Pregnant women who intend to have antenatal examinations and delivery at Beijing Obstetrics and Gynecology Hospital Pregnant women who are willing to participate in this study with informed consent  Exclusion Criteria:  Women with Hepatitis B, syphilis, HIV/AIDS and other infectious diseases.