Table 1.
Descriptive statistics for study participants from the MoBa cohort
| Baseline cohort at birth with NO2 data (n=17 533) | Questionnaire at 6 months (n=14 386) |
Questionnaire at 18 months (n=12 231) |
|
| Oslo | 4 669 (26.6) | 3 801 (26.4) | 3 320 (27.1) |
| Akershus | 7 554 (43.1) | 6 284 (43.7) | 5 350 (43.7) |
| Bergen | 3 869 (22.1) | 3 135 (21.8) | 2 591 (21.2) |
| Hordaland | 1 441 (8.2) | 1 166 (8.1) | 970 (7.9) |
| LRTI 0–6 months | 653 (4.5) | ||
| Missing | 500 (3.5) | ||
| LRTI 6–18 months | 1 469 (12.0) | ||
| Missing | 230 (1.9) | ||
| Wheeze 6–18 months | 4 961 (40.6) | ||
| Missing | 255 (2.1) | ||
| Women who changed address during pregnancy | 2 336 (13.3) | 1 782 (12.4) | 1 471 (12.0) |
| Parity | |||
| 0 | 8 310 (47.4) | 6 973 (48.5) | 6 003 (49.1) |
| 1 | 6 328 (36.1) | 5 138 (35.7) | 4 310 (35.2) |
| ≥2 | 2 895 (16.5) | 2 275 (15.8) | 1 918 (15.7) |
| Sex of child | |||
| Boy | 8 925 (50.9) | 7 285 (50.6) | 6 177 (50.5) |
| Girl | 8 608 (49.1) | 7 101 (49.4) | 6 054 (49.5) |
| Maternal age at delivery, years | 31.0±4.5 | 31.1±4.4 | 31.2±4.3 |
| Marital status | |||
| Married/cohabiting | 16 780 (95.7) | 13 839 (96.2) | 11 797 (96.5) |
| Other | 753 (4.3) | 547 (3.8) | 434 (3.6) |
| Maternal education | |||
| Less than high school | 986 (5.6) | 713 (5.0) | 547 (4.5) |
| High school | 4 175 (23.8) | 3 465 (24.1) | 2 845 (23.3) |
| Up to 4 years of college | 6 480 (37.0) | 5 677 (39.5) | 4 919 (40.2) |
| More than 4 years of college (master or professional degree) | 4 867 (27.8) | 4 254 (29.6) | 3 731 (30.5) |
| Missing | 1 025 (5.9) | 277 (1.9) | 189 (1.6) |
| Maternal smoking during pregnancy | 1 085 (6.2) | 843 (5.9) | 675 (5.5) |
| Missing | 1 000 (5.7) | 263 (1.8) | 185 (1.5) |
| Maternal prepregnancy body mass index* | 23.5±3.8 | 23.5±3.7 | 23.5±3.7 |
| Maternal atopy | 5 802 (33.1) | 4 947 (34.4) | 4 276 (35.0) |
| Season of birth | |||
| Winter | 4 099 (23.4) | 3 352 (23.3) | 2 858 (23.4) |
| Spring | 4 686 (26.7) | 3 851 (26.8) | 3 191 (26.1) |
| Summer | 4 630 (26.4) | 3 827 (26.6) | 3 312 (27.1) |
| Autumn | 4 118 (23.5) | 3 356 (23.3) | 2 870 (23.5) |
Numbers are n (%) or mean±SD deviation.
*Missing data for maternal prepregnancy body mass index: baseline cohort 1549 (8.8%), at 6 months 693 (4.8%), at 18 months 522 (4.3%).
LRTI, lower respiratory tract infections; MoBa, Norwegian Mother and Child Cohort Study.