Table 1. Characteristics of study participants according to gestational diabetes (GDM) case-control status.
| Characteristics | GDM Cases | Controls | P-value |
| (N = 57) | (N = 114) | ||
| n (%) | n (%) | ||
| Maternal Age at interview (years) | 34.3±4.81 | 33.1±3.9 | 0.09 |
| <35 | 29 (50.9) | 72 (63.2) | 0.12 |
| ≥35 | 28 (41.1) | 42 (36.8) | |
| Maternal Race/Ethnicity | |||
| White/Non-Hispanic | 40 (70.2) | 96 (84.2) | 0.03 |
| African American | 2 (3.5) | 6 (5.3) | |
| Others | 15 (26.3) | 12 (10.5) | |
| Nulliparous | 27 (47.4) | 62 (54.4) | 0.39 |
| Consumed Prenatal Vitamins | 49 (86.0) | 105 (92.1) | 0.21 |
| Consumed≥2 Servings of Fish Weekly | 27 (47.4) | 65 (57.0) | 0.23 |
| Consumed≥1 Glass of Milk Daily | 22 (38.6) | 42 (36.8) | 0.82 |
| Smoked During Pregnancy | 3 (5.3) | 7 (6.1) | 0.82 |
| Family History of Diabetes Mellitus | 14 (24.6) | 15 (13.2) | 0.06 |
| Physical Inactivity During Pregnancy | 9 (15.8) | 9 (7.9) | 0.11 |
| Pre-Pregnancy Body Mass Index (kg/m2) | 26.7±7.21 | 23.3±3.8 | 0.001 |
| Pre-Pregnancy Body Mass Index (kg/m2) | |||
| <25 | 29 (50.9) | 84 (73.7) | 0.003 |
| ≥25 | 28 (49.1) | 30 (26.3) | |
| Gestational Age at Blood Collection (weeks) | 16.3±2.11 | 16.1±2.2 | 0.59 |
| Gestational Age at Glucose Screening Test (weeks) | 26.9±2.61 | 26.4±2.5 | 0.25 |
| Season of Estimated Time of Conception* | |||
| (March–May) Spring | 21 (36.8) | 42 (36.8) | 1.00 |
| (June–August) Summer | 17 (29.8) | 34 (29.8) | |
| (September–November) Autumn | 13 (22.8) | 26 (22.8) | |
| (December–February) Winter | 6 (10.5) | 12 (10.5) | |
| Maternal Plasma 25-Hydroxyvitamin D Concentrations (ng/ml) | |||
| Mean±SD | 24.2±8.51 | 30.1±9.7 | <0.001 |
1
Mean±SD (standard deviation).
*
Matched factor.