Factors showing change in the risk of SIDS during the periods studied
| 1984–1989 (period 1) | 1990–1992 (period 2) | 1993–1998 (period 3) | p value for interaction with period | |||||||||||||
| Factor |
SIDS No (%) |
Control No (%) |
Odds ratio (95% CI) | p value |
SIDS No (%) |
Control No (%) |
Odds ratio (95% CI) | p value |
SIDS No (%) |
Control No (%) |
Odds ratio (95% CI) | p value | ||||
| Maternal smoking during pregnancy | 46 (42) | 75 (33) | 1.52 (0.94 to 2.37) | 0.09 | 10 (40) | 26 (43) | 0.87 (0.33 to 2.29) | 0.78 | 21 (55) | 25 (30) | 3.37 (1.37 to 8.25) | 0.01 | Overall: 0.12 1 v2: 0.31 1 v 3: 0.13 2v 3: 0.04 | |||
| Maternal age | ||||||||||||||||
| <21 y | 9 (9) | 13 (6) | 1.42 (0.52 to 3.85) | 0.54 | 3 (12) | 2 (3) | 2.58 (0.40 to 16.52) | 0.58 | 5 (13) | 1 (1) | 22.49 (2.30 to 219.80) | 0.01 | Overall: 0.05 1v 2: 0.86 1 v 3: 0.01 2 v 3: 0.06 | |||
| 21–25 y | 24 (23) | 62 (27) | 0.68 (0.36 to 1.27) | 6 (23) | 21 (34) | 0.60 (0.20 to 1.84) | 15 (40) | 12 (15) | 17.77 (3.15 to 100.28) | |||||||
| 26–30 y | 43 (41) | 89 (38) | 1.0 (ref) | 10 (38) | 20 (33) | 1.0 (ref) | 8 (21) | 36 (45) | 1.0 (ref) | |||||||
| 31–35 y | 21 (20) | 56 (24) | 0.71 (0.38 to 1.36) | 6 (23) | 15 (25) | 0.70 (0.23 to 2.19) | 7 (18) | 26 (33) | 1.33 (0.37 to 4.71) | |||||||
| >35 y | 8 (7) | 11 (5) | 1.35 (0.48 to 3.83) | 1 (4) | 3 (5) | 0.79 (0.08 to 7.97) | 3 (8) | 5 (6) | 5.62 (0.71 to 44.37) | |||||||