Table 1 Association of preterm birth and vitamin D concentrations
From: Vitamin D deficiency in pregnancy and the risk of preterm birth: a nested case–control study
Total N = 930 (%) | Term n = 668 (%) | Preterm n = 262 (%) | OR (95% CI) | P-value | |
|---|---|---|---|---|---|
25(OH)D concentration (quartiles) | |||||
Highest quartile (≥ 48.53 nmol/L) | 232 (25.0) | 177 (26.5) | 56 (21.4) | Reference | |
2nd quartile (38.0–48.52 nmol/L) | 233 (25.0) | 172 (25.8) | 60 (22.9) | 1.13 (0.74–1.72) | 0.574 |
3rd quartile (30.25–37.99 nmol/L) | 232 (25.0) | 167 (25.0) | 66 (25.2) | 1.24 (0.82–1.88) | 0.306 |
Lowest quartile (≤ 30.25 nmol/L) | 233 (25.0) | 152 (22.8) | 80 (30.5) | 1.67 (1.12–2.51) | 0.013 |
25(OH)D concentrations (two categories) | |||||
Not deficient (upper three quartiles) | 697 (75%) | 516 (77.2) | 182 (69.5) | Reference | |
Deficient (lowest quartile) | 233 (25%) | 152 (22.8) | 80 (30.5) | 1.49 (1.08–2.05) | 0.014 |