TABLE 1.
Baseline characteristics comparing 350 women with GDM with 349 women without GDM, nested within the Danish National Birth Cohort1
| Cases (n = 350) | Controls (n = 349) | P | |
| Age at birth, y | 32.2 ± 4.3 | 29.9 ± 4.2 | <0.0001 |
| Socioeconomic status (highest-level professional)2 | 60 (18.1) | 78 (22.5) | 0.10 |
| Graduated high school | 100 (38.1) | 124 (53.0) | 0.003 |
| Cohabitation status (pairs) | 329 (99.1) | 345 (98.9) | 0.75 |
| Family history of diabetes | 97 (28.0) | 28 (8.0) | <0.0001 |
| History of metabolic disorders | 11 (3.3) | 4 (1.2) | 0.05 |
| History of anemia | 52 (15.6) | 53 (15.2) | 0.99 |
| Iron-deficient anemia | 20 (6.0) | 15 (4.3) | 0.54 |
| Height, cm | 167.1 ± 6.0 | 168.7 ± 6.3 | 0.001 |
| Prepregnancy weight, kg | 80.1 ± 17.8 | 68.4 ± 13.8 | <0.0001 |
| Prepregnancy BMI, kg/m2 | 28.7 ± 6.0 | 24.1 ± 4.6 | <0.0001 |
| Prepregnancy BMI by category, kg/m2 | <0.0001 | ||
| ≤18.5 | 2 (0.6) | 9 (2.6) | |
| >18.5 to <25 | 98 (30.3) | 220 (64.5) | |
| ≥25 to <30 | 103 (31.9) | 73 (21.4) | |
| ≥30 to <35 | 77 (23.8) | 26 (7.6) | |
| ≥35 to <40 | 31 (9.6) | 10 (2.9) | |
| ≥40 | 12 (3.7) | 3 (0.9) | |
| Anemia (ever) | 52 (14.9) | 53 (15.2) | 0.90 |
| Nonsmoker | 242 (70.1) | 265 (75.9) | 0.38 |
| Any exercise during pregnancy | 100 (30.0) | 141 (40.4) | 0.005 |
| Gravidity (0) | 85 (25.5) | 143 (41.1) | 0.0002 |
| Primiparity | 128 (37.9) | 175 (51.6) | 0.02 |
| Plasma biomarkers in early pregnancy | |||
| sTfR, mg/L | 1.5 ± 0.7 | 1.4 ± 0.6 | 0.002 |
| Ferritin, μg/L | 80.6 ± 56.0 | 71.8 ± 50.1 | 0.03 |
| Ferritin:sTfR ratio | 67.4 ± 77.3 | 64.1 ± 69.5 | 0.55 |
| ox-LDL, U/L | 24.8 ± 6.80 | 23.4 ± 7.9 | 0.01 |
| CRP, mg/L | 6.5 ± 6.7 | 3.7 ± 5.3 | <0.0001 |
Continuous variables are expressed as means ± SDs and categorical data are expressed as n (%). Percentage missing for cases compared with controls: education level, 27% compared with 33%; family history of diabetes, 34% compared with 46%; anemia late in pregnancy, 11% compared with 10%; and anemia in the last weeks of pregnancy, 22% compared with 26%. CRP, C-reactive protein; GDM, gestational diabetes mellitus; ox-LDL, oxidized LDL; sTfR, soluble transferrin receptor.
Socioeconomic status was defined by Statistics Denmark (17). The category “highest-level professional” included management at the highest levels in corporations, companies, organizations, and the public sector, or work that requires skills at the highest level for each discipline.