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Table 1 Patients and IVF cycle characteristics by serum 25 (OH) D quartiles

From: Effect of vitamin D status on normal fertilization rate following in vitro fertilization

Parameter Group1 Group2 Group 3 Group 4 P value
Number of cycles 216 210 211 211  
Serum 25(OH) D (ng/ml)
 Median 9.04 13.67 16.20 23.22  
 Range 4.92–11.20 11.25–14.00 14.10–18.60 18.70–39.51  
Age(y) 31.65 ± 3.32 31.86 ± 3.94 31.31 ± 3.44 31.88 ± 3.69 0.331
Duration of infertility(y) 3.53 ± 2.19 3.85 ± 2.76 3.68 ± 2.31 3.61 ± 2.38 0.543
BMI (kg/m2) 23.93 ± 3.61 23.37 ± 3.30 23.16 ± 3.28 23.46 ± 3.33 0.099
AMH (ng/ml) 7.21 ± 5.50 6.05 ± 4.37 6.93 ± 5.61 6.68 ± 5.51 0.134
bFSH (mIU/ml) 6.75 ± 1.77 7.04 ± 2.03 6.88 ± 1.95 6.57 ± 1.68 0.063
Season of blood drawing
 Spring (n, %) 55,25.5% 39,18.6% 25,11.8% 24,11.4% <0.001*
 Summer (n, %) 78,36.1% 71,33.8% 55,26.1% 41,19.4%
 Autumn (n, %) 22,10.2% 43,20.5% 76,36.0% 74,35.1%
 Winter (n, %) 61,28.2% 57,27.1% 55,26.1% 72,34.1%
Previous pregnancy
 NO (n, %) 106 (49.1%) 87 (41.4%) 111 (52.6%) 103 (48.8%) 0.134
 Yes (n, %) 110 (50.9%) 123 (58.6%) 100 (47.4%) 108 (51.2%)
Infertility diagnosis
 Male factor (n, %) 5 (2.3%) 11 (5.2%) 10 (4.7%) 10 (4.7%) 0.837
 Tubal factor (n, %) 135 (62.8%) 131 (62.4%) 122 (57.8%) 125 (59.2%)
 Mixed (n, %) 24 (11.2%) 28 (13.3%) 26 (12.3%) 28 (13.3%)
 Endometriosis (n, %) 7 (3.3%) 11 (5.2%) 13 (6.2%) 14 (6.6%)
 Anovulatory (n, %) 41 (19.1%) 27 (12.9%) 37 (17.5%) 32 (15.2%)
 Unexplained (n, %) 3 (1.4%) 2 (1.0%) 3 (1.4%) 2 (0.9%)
COH protocol
 Luteal phase agonist (n, %) 151 (69.9%) 143 (68.1%) 159 (75.4%) 158 (74.9%) 0.250
 Antagonist (n, %) 65 (30.1%) 67 (31.9%) 52 (24.6%) 53 (25.1%)
Duration of stimulation (d) 9.06 ± 2.17 9.04 ± 2.34 8.81 ± 2.20 9.05 ± 2.50 0.631
Follicle≥16 mm on HCG day 10.26 ± 4.94 9.01 ± 4.73 9.86 ± 5.55 9.68 ± 5.02 0.083
Endometrial thickness on HCG day (mm) 11.62 ± 2.71 11.30 ± 2.21 11.36 ± 2.32 11.49 ± 2.45 0.536
Progestrone on HCG day (ng/ml) 0.86 ± 0.28 0.90 ± 0.29 0.94 ± 0.34 0.94 ± 0.32 0.143
Peak estradiol (pg/ml) 3737.49 ± 2178.84 3398.98 ± 2227.44 3593.33 ± 2352.79 3569.79 ± 2231.67 0.540
Oocytes retrieved (n) 11.47 ± 5.53 10.12 ± 4.78 10.79 ± 5.43 10.68 ± 5.56 0.078
Mature oocytes (n) 9.45 ± 4.80 8.40 ± 4.14 9.05 ± 4.66 8.97 ± 4.54 0.119
Normal fertilization rate (%) 69.62 ± 17.85 71.69 ± 19.92 73.82 ± 18.36 75.43 ± 17.39 0.007* <0.001a*
High quality embryo rate (%) 67.5% 67.2% 65.3% 67.7% 0.465
Blastocyst formation rate (%) 66.86 ± 28.60 62.48 ± 33.21 65.84 ± 31.27 67.96 ± 28.87 0.332
Embryos transferred (n) 1.93 ± 0.26 1.92 ± 0.28 1.97 ± 0.18 1.95 ± 0.22 0.340
  1. *Values are significantly different between groups (P < 0.05)
  2. aAdjusted for maternal age, BMI, AMH, infertility diagnosis, season of blood draw, COH protocol, previous pregnancy, duration of stimulation, E2 levels on the day of hCG, number of larger follicles, number of oocytes retrieved and number of mature oocytes