Table 3 Demographic characteristics of KD and control cases and potential perinatal factors for KD development (frequencies, means and logistic regression with p-value, OR and 95% CI)
|  | KD cases (n = 308) | Control cases (n = 326) | Conditional logit – model (n = 454) Unconditional logit - model (n = 542) | |
|---|---|---|---|---|
| Â | Â | OR [95% CI] | p-value | |
Duration of pregnancy in weeks | ||||
 Average (±SD) | 39 (±2.057) | 39 (±1.944) | 0.992 [0.891–1.105] 0.965 [0.883–1.050] | 0.891 0.414 |
Parturitiona, n (%) | ||||
 Vaginal | 128 (65.6) | 194 (70.8) | 1 (reference) | 0.388 0.302 |
 Cesarean section | 67 (34.4) | 80 (29.2) | 1.286 [0.727–2.274] 1.259 [0.813–1.953] | |
Birth weight in gram | ||||
 Average (±SD) | 3340 (±527.052) | 3383 (±537.734) | 0.999 [0.999–1.000] 0.999 [0.999–1.000] | 0.715 0.399 |
 Range | 1560 – 4960 | 1171 – 4910 |  |  |
Duration of breastfeeding, n (%) | ||||
  <  2 weeks | 66 (21.4) | 30 (9.2) | 1 (reference) | 0.013 0.001 |
  >  2 weeksb | 242 (78.6) | 296 (90.8) | 0.471 [0.260–0.853] 0.415 [0.243–0.687] | |
Vitamin D supplementation in the first year of life, n (%) | ||||
 No | 64 (20.8) | 53 (16.3) | 1 (reference) | 0.782 0.051 |
 Yes | 244 (79.2) | 273 (83.7) | 0.926 [0.537–1.595] 0.623 [0.383–0.995] | |
Duration of vitamin D supplementation in the first year of life in months | ||||
 Mean (±SD) | 5.16 (±5.749) | 6.03 (±5.596) | 0.964 [0.931–0.998] 0.965 [0.935–0.995] | 0.039 0.024 |
Regularity of vitamin D supplementationc, n (%) | ||||
 Irregular | 65 (26.6) | 55 (20.0) | 1 (reference) | 0.042 0.060 |
 Regular | 179 (73.4) | 220 (80.0) | 0.559 [0.319–0.980] 0.642 [0.402–1.016] | |