Table 1.
Demographics of the study population
| Wales | Denmark | |||
| Non-CF population | CF population | Non-CF population | CF population | |
| N | 442 409 | 255 | 1 736 186 | 597 |
| Birth weight in g (median (IQR)) |
3400.00 (3060.00, 3740.00) |
3200.00 (2845.00, 3567.50) |
3500.00 (3150.00, 3850.00) |
3300.00 (2900.00, 3700.00) |
| Low birth weight=yes (%) | 24 035 (5.4) | 28 (11.0) | 72 480 (4.2) | 71 (11.9) |
| Gestational age in weeks (median (IQR)) |
40.00 (39.00, 41.00) |
39.00 (38.00, 40.00) |
40.00 (39.00, 41.00) |
39.71 (38.00, 40.43) |
| Preterm=yes (%) | 25 770 (5.8) | 24 (9.4) | 87 317 (5.0) | 76 (12.7) |
| Sex=male (%) | 215 238 (48.7) | 116 (45.5) | 891 336 (51.3) | 320 (53.6) |
| First-born=yes (%) | 205 805 (46.5) | 122 (47.8) | 523 457 (30.1) | 179 (29.8) |
| Mother’s age at birth (median (IQR)) |
27.94 (23.67, 32.35) |
27.06 (23.07, 31.78) |
29.00 (25.00, 32.00) |
28.00 (24.00, 31.00) |
| Mother smoked year prior pregnancy | ||||
| No (%) | 79 208 (17.9) | 48 (18.8) | 911 436 (52.5) | 239 (40.0) |
| Yes (%) | 42 449 (9.6) | 20 (7.8) | 286 993 (16.5) | 72 (12.1) |
| NA (%) | 320 752 (72.5) | 187 (73.3) | 537 757 (31.0) | 286 (47.9) |
| WIMD quintile* | ||||
| 1 (%) | 109 986 (24.9) | 68 (26.7) | NA | NA |
| 2 (%) | 98 595 (22.3) | 58 (22.7) | NA | NA |
| 3 (%) | 87 144 (19.7) | 36 (14.1) | NA | NA |
| 4 (%) | 76 076 (17.2) | 48 (18.8) | NA | NA |
| 5 (%) | 70 608 (16.0) | 45 (17.6) | NA | NA |
| Maternal education† | ||||
| Primary or lower secondary (%) | NA | NA | 490 215 (28.2) | 218 (36.5) |
| Upper secondary or postsecondary non-tertiary (%) |
NA | NA | 733 037 (42.2) | 233 (39.0) |
| Tertiary education or not known (%) | NA | NA | 512 934 (29.5) | 146 (24.5) |
| Diabetes=no (%) | NA | NA | 1 734 670 (99.9) | 590 (98.8) |
| Pre-eclampsia=no (%) | NA | NA | 1 733 619 (99.9) | ‡ |
| Mode of delivery | ||||
| Vaginal (%) | NA | NA | 1 249 816 (72.0) | 402 (67.3) |
| Elective caesarean section (%) | NA | NA | 79 127 (4.6) | 21 (3.5) |
| Emergency caesarean section (%) | NA | NA | 83 866 (4.8) | 21 (3.5) |
| NA (%) | NA | NA | 323 377 (18.6) | 153 (25.6) |
*WIMD, where 1=most deprived and 5=least deprived.
†Original levels are grouped together as follows: ‘primary education, first stage of basic education’ and ‘lower secondary education, second stage of basic education’ are grouped into ‘primary or lower secondary education’; ‘upper secondary education’ and ‘postsecondary, non-tertiary education’ are grouped into ‘upper secondary or postsecondary non-tertiary’; ‘first stage of tertiary education’, ‘second stage of tertiary education’ and ‘not known’ are grouped into ‘tertiary education or not known’.
‡Omitted due to cells containing five or fewer individuals or because it would allow the calculation of a cell with five or fewer individuals.
CF, cystic fibrosis; NA, not available; WIMD, Welsh Index of Multiple Deprivation.