Cases* | Risk time† | Crude HR (95% CI) | Adjusted‡ HR (95% CI) | |
Continuous exposure§ | ||||
Ten night shifts | 1.13 (1.01 to 1.27) | 1.15 (1.02 to 1.29) | ||
Categorical exposure | ||||
No night shifts | 1 149 | 226 184 | 1 | 1 |
1–10 night shifts | 646 | 113 058 | 1.03 (0.93 to 1.13) | 1.05 (0.94 to 1.16) |
11–20 night shifts | 78 | 30 060 | 1.21 (0.96 to 1.53) | 1.20 (0.94 to 1.53) |
21–25 night shifts | 8 | 4 348 | 1.59 (0.79 to 3.19) | 1.70 (0.84 to 3.42) |
26+night shifts | 8 | 4 246 | 2.48 (1.23 to 5.00) | 2.62 (1.30 to 5.29) |
*Miscarriages.
†Pregnancy weeks.
‡Adjusted for maternal age, BMI and smoking during pregnancy, parity, SES, former miscarriages.
§Effect per additional night shift during pregnancy week 3–21.