Table 1 Baseline characteristics from index pregnancy according to GDM history
From: Breast cancer in women with previous gestational diabetes: a nationwide register-based cohort study
|  | GDM (n = 24,140) | No GDM (n = 683,981) | P value |
|---|---|---|---|
Clinical characteristics | Â | Â | Â |
Age (years) | 28 (25–32) | 28 (25–31) | < 0.001 |
Primiparity | 20,277 (84.0) | 531,526 (77.7) | < 0.001 |
Pregestational BMI (kg/m2)a | 27.2 (23.1–31.6) | 22.8 (20.7–25.8) | < 0.001 |
Smoking during pregnancyb | 3,832 (17.4) | 102,931 (17.4) | 0.841 |
Preexisting hypertension | 594 (2.5) | 8,746 (1.3) | < 0.001 |
Preexisting metformin treatment | 674 (2.8) | 5,015 (0.7) | < 0.001 |
Preexisting cancer (not breast) | 38 (0.2) | 1,142 (0.2) | 0.721 |
Preexisting carcinoma in situ (not breast) | 31 (0.1) | 1,310 (0.2) | 0.027 |
No preexisting comorbidityc | 23,798 (98.6) | 677,242 (99.0) | < 0.001 |
Demographic characteristics | Â | Â | Â |
Ethnicity | Â | Â | Â |
 Danish | 19,169 (79.4) | 602,906 (88.1) | < 0.001 |
 Immigrant, Western | 625 (2.6) | 21,473 (3.1) | < 0.001 |
 Immigrant, Non-Western | 3,745 (15.5) | 49,138 (7.2) | < 0.001 |
 Descendantd | 601 (2.5) | 10,464 (1.5) | < 0.001 |
Marital status | Â | Â | Â |
 Single/not living with a partner | 2,914 (12.1) | 84,200 (12.3) | 0.266 |
 Married/living with a partner | 21,226 (87.9) | 599,781 (87.7) | 0.266 |
Income, tertile | Â | Â | Â |
 Low | 7,968 (33.0) | 214,526 (31.4) | < 0.001 |
 Middle | 7,694 (31.9) | 234,543 (34.3) | < 0.001 |
 High | 8,478 (35.1) | 234,912 (34.3) | 0.013 |
Highest completed education | Â | Â | Â |
 Lower secondary | 5,891 (24.4) | 132,315 (19.3) | < 0.001 |
 Upper secondary | 10,064 (41.7) | 287,527 (42.0) | 0.283 |
 Post secondary | 8,185 (33.9) | 264,139 (38.6) | < 0.001 |
Occupation | Â | Â | Â |
 Employed | 16,495 (68.3) | 491,945 (71.9) | < 0.001 |
 Unemployed or on welfare payment | 2,759 (11.4) | 89,650 (13.1) | < 0.001 |
 Under education | 3,160 (13.1) | 68,731 (10.0) | < 0.001 |
 Early retirement | 274 (1.1) | 3,203 (0.5) | < 0.001 |
Obstetrical characteristics | Â | Â | Â |
Preeclampsia | 1704 (7.1) | 23,850 (3.5) | < 0.001 |
Gestational hypertension | 966 (4.0) | 11,019 (1.6) | < 0.001 |
Preterm delivery | 2473 (10.2) | 46,119 (6.7) | < 0.001 |