Between March 2016 and March 2017, we performed a large retrospective, non-interventional, single-center cohort study and measured 25(OH)D3 plasma levels prior to ovarian stimulation in couples who underwent IVF/ICSI.And we analysed the correlation of vitamin D status and reproductive capacity .

Before conducting ovarian stimulation, all couples must conduct preoperative routine examination such as routine blood test, blood group examination and infectious disease examination. We collected 2ml remaining blood from the examination by use of sodium heparin, which then conducted 1,25(OH)2D3 assay by liquid chromatography-tandem mass spectrometry.

All patients underwent a standardized ovarian stimulation regimen, oocyte retrieval, and fertilization, followed by a planned fresh or frozen embryo transfer.Normal fertilization rate was defined as the presence of two pronuclei (2PN) at the time of fertilization assessment, 16-19 h after ICSI or conventional insemination. The percentage of top quality embryos was defined as the percentage of top quality embryos among the total number of 2PN embryos. Blastocyst forming rate was calculated as number of formed blastocysts devided by number of cultured blastocysts.

Inclusion Criteria:

• couples who underwent IVF/ICSI.

Exclusion Criteria:

• sperm or egg donation, PGD or PGS,TESA or PESA, ovum frozen ,no oocyte for fertilization.

non-interventional, single-center cohort study and measured 25(OH) D plasma levels prior to ovarian stimulation in couples who underwent IVF/ICSI.