Table 1.
Maternal age, parity and smoking habits in births of females with IJD and reference births from the general population by year of delivery, Norway 1967-2009
| Period | Groups | Number of births per period n | Proportion of births in women with IJD compared to references (%) | Maternal age at delivery (years) mean (SD) | p-value | Parity mean (SD) | p-value | Smoking at time of conception (%) | p-value |
|---|---|---|---|---|---|---|---|---|---|
| 1967-1979 | IJD women | 645 | 0.08 | 28.2 (5.6) | <0.001 | 1.0 (1.1) | 0.6 | n.a. | |
| References | 773563 | 26.2 (5.3) | 1.0 (1.1) | n.a. | |||||
| 1980-1989 | IJD women | 1613 | 0.3 | 28.3 (5.1) | <0.001 | 0.8 (0.9) | 0.2 | n.a. | |
| References | 517621 | 27.3 (5.0) | 0.9 (1.0) | n.a. | |||||
| 1990-1999 | IJD women | 2508 | 0.4 | 29.7 (5.2) | <0.001 | 1.0 (1.1) | 0.007 | n.a. | |
| References | 581627 | 28.7 (5.0) | 0.9 (1.0) | n.a. | |||||
| 2000-2009 | IJD women | 2736 | 0.5 | 31.1 (5.1) | <0.001 | 1.0 (1.1) | <0.001 | 22.9 | p < 0.0001 |
| References | 564299 | 30.0 (5.1) | 0.9 (1.0) | 19.4 |
IJD inflammatory joint disease, SD standard deviation, n.a. not applicable