TABLE 1.
Baseline characteristics of the study participants according to serum 25(OH)D concentrations1
| Quartiles of serum 25(OH)D concentrations |
|||||
| Q1 | Q2 | Q3 | Q4 | P | |
| Serum 25(OH)D concentration, nmol/L | |||||
| Median | 65.0 | 83.1 | 92.4 | 115.0 | |
| Range | 33.5–75.0 | 75.9–86.2 | 86.8–104.6 | 107.8–155.5 | |
| Women, n | 25 | 25 | 25 | 25 | |
| Treatment cycles,2 n | 45 | 41 | 40 | 42 | |
| Age, y | 35.6 ± 3.9 | 34.5 ± 3.3 | 34.9 ± 3.9 | 34.2 ± 4.0 | 0.50 |
| Race/ethnic group, n (%) | 0.20 | ||||
| White/Caucasian | 17 (68.0) | 21 (84.0) | 23 (92.0) | 21 (84.0) | |
| Other | 8 (32.0) | 4 (16.0) | 2 (8.0) | 4 (16.0) | |
| BMI, kg/m2 | 26.2 ± 4.5 | 23.1 ± 3.2 | 24.3 ± 4.5 | 23.9 ± 3.1 | 0.04 |
| Ever smoker, n (%) | 6 (24.0) | 8 (32.0) | 4 (16.0) | 11 (44.0) | 0.18 |
| Educational level, n (%) | 0.41 | ||||
| College degree or higher | 22 (88.0) | 22 (88.0) | 23 (92.0) | 20 (80.0) | |
| Physical activity, h/wk | 3.6 ± 3.5 | 5.6 ± 4.5 | 4.3 ± 4.1 | 6.4 ± 6.0 | 0.26 |
| Dietary characteristics | |||||
| Vitamin B-12 concentration, pg/mL | 519 ± 243 | 605 ± 197 | 671 ± 392 | 612 ± 203 | 0.21 |
| Folic acid concentration, ng/mL | 26.1 ± 23.7 | 31.0 ± 30.7 | 26.0 ± 21.5 | 25.0 ± 8.0 | 0.18 |
| Vitamin D intake, IU/d | 557 ± 252 | 667 ± 360 | 582 ± 271 | 778 ± 460 | 0.10 |
| Multivitamin use, n (%) | 21 (84.0) | 23 92.0) | 24 (96.0) | 23 (92.0) | 0.62 |
| Prudent Diet Pattern score | −0.27 ± 0.6 | 0.07 ± 1.2 | −0.26 ± 0.8 | 0.12 ± 1.0 | 0.32 |
| Western Diet Pattern score | 0.07 ± 0.9 | −0.24 ± 0.8 | −0.00 ± 0.8 | 0.16 ± 0.8 | 0.41 |
| Reproductive characteristics | |||||
| Season of blood draw, n (%) | 0.40 | ||||
| Spring | 9 (36.0) | 5 (20.0) | 4 (16.0) | 7 (28.0) | |
| Summer | 4 (16.0) | 4 (16.0) | 7 (28.0) | 8 (32.0) | |
| Autumn | 4 (16.0) | 9 (36.0) | 9 (36.0) | 7 (28.0) | |
| Winter | 8 (32.0) | 7 (28.0) | 5 (20.0) | 3 (12.0) | |
| Primary infertility diagnosis, n (%) | 0.41 | ||||
| Male factor | 10 (40.0) | 9 (36.0) | 11 (44.0) | 5 (20.0) | |
| Diminished ovarian reserve | 1 (4.0) | 1 (4.0) | 0 (0.0) | 1 (4.0) | |
| Ovulatory | 2 (8.0) | 1 (4.0) | 4 (16.0) | 3 (12.0) | |
| Other female factors | 2 (8.0) | 2 (8.0) | 2 (8.0) | 5 (20.0) | |
| Unexplained | 10 (40.0) | 12 (48.0) | 8 (32.0) | 11 (44.0) | |
| Initial treatment protocol, n (%) | 0.57 | ||||
| Antagonist | 3 (12.0) | 2 (8.0) | 3 (12.0) | 2 (8.0) | |
| Flare | 3 (12.0) | 0 (0.0) | 2 (8.0) | 4 (16.0) | |
| Luteal phase agonist | 19 (76.0) | 23 (92.0) | 20 (80.0) | 19 (76.0) | |
| Day 3 follicle-stimulating hormone, IU/L | 7.3 ± 2.2 | 7.2 ± 1.9 | 6.7 ± 2.1 | 6.8 ± 2.0 | 0.83 |
| Treatment cycles per woman, n (%) | 0.73 | ||||
| One | 17 (68.0) | 15 (60.0) | 15 (60.0) | 13 (52.0) | |
| Two | 3 (12.0) | 7 (28.0) | 7 (28.0) | 7 (28.0) | |
| ≥Three | 5 (20.0) | 3 (12.0) | 3 (12.0) | 5 (20.0) | |
| Previous in vitro fertilization, n (%) | 7 (28.0) | 6 (24.0) | 6 (24.0) | 3 (12.0) | 0.57 |
| Previous intrauterine insemination, n (%) | 9 (36.0) | 12 (48.0) | 10 (40.0) | 9 (36.0) | 0.80 |
1
Values are means ± SDs unless otherwise indicated. Q, quartile; 25(OH)D, 25-hydroxyvitamin D.
2
Total number of assisted reproductive technology treatment cycles (in vitro fertilization or intracytoplasmic sperm injection) for the women included in each quartile of serum 25(OH)D concentration.