The Cohort Study of the Correlation Between Serum 25(OH)D Level and Pregnancy Outcome

Inclusion Criteria: * ≥20 years old * The chromosome karyotype of the couple is normal * Color ultrasound examination results indicated that there was no organic disease related to reproductive tract * No serious complications of surgery and medicine * Agree and voluntarily sign informed consent Exclusion Criteria: * There are contraindications to pregnancy * the initiative to give up pregnancy * Severe medical and surgical complications, for example, liver disease was defined as serum alanine aminotransferase \[ALT\] or aspartic aminotransferase \[AST\]\>3 x upper normal limit \[ULN\] after repeated testing * Concomitant malignant tumor, malignant tumor developed in the last 5 years (except for the skin squamous basal cell carcinoma that has been removed and considered cured). Subjects who developed malignant tumors more than 5 years ago should provide evidence of remission or cure. Subjects with a history of cervical cancer were eligible if they could demonstrate that their cervical cancer had been cone removed or cured within the past 3 years * Known human immunodeficiency virus (HIV) positive and/or hepatitis B surface antigen or hepatitis C virus antibody positive at screening visit * With a history of chronic infections such as mycoplasma, chlamydia, cryptococcus, and invasive fungal infections should be discussed with the principal investigator