Multivariable adjusted association between residing in a Q fever-affected area in 2008–2010 and three adverse pregnancy outcomes
| Variable | Category | Preterm delivery, OR (95% CI) | Child small for gestational age, OR (95% CI) | Perinatal mortality, OR (95% CI) |
|---|---|---|---|---|
| Residing in a Q fever-affected area | Yes | 1.00 (0.95 to 1.05) | 1.10 (1.05 to 1.14) | 0.96 (0.85 to 1.09) |
| No | Reference | Reference | Reference | |
| Period | 2003–2004 | Reference | Reference | Reference |
| 2008–2010 | 0.92 (0.89 to 0.95) | 0.82 (0.80 to 0.84) | 0.71 (0.65 to 0.77) | |
| Interaction term: residing in a Q fever-affected area×period† | Yes, in 2008–2010 | 1.01 (0.94 to 1.08) | 1.06 (1.01 to 1.12) | 0.87 (0.72 to 1.05) |
| Reference group* | Reference | Reference | Reference | |
| Age of the mother (years) | <20 | 1.47 (1.34 to 1.61) | 1.26 (1.17 to 1.36) | 1.17 (0.91 to 1.51) |
| 20–35 | Reference | Reference | Reference | |
| ≥35 | 1.02 (0.98 to 1.06) | 1.06 (1.03 to 1.09) | 1.33 (1.21 to 1.45) | |
| Ethnic background | Western | Reference | Reference | Reference |
| Non-Western | 1.02 (0.98 to 1.06) | 1.22 (1.18 to 1.26) | 1.68 (1.53 to 1.85) | |
| Smoking | Heavy smoking | 1.71 (1.39 to 2.09) | 3.36 (2.92 to 3.87) | 1.67 (0.98 to 2.84) |
| Non-heavy smoking | Reference | Reference | Reference | |
| Socioeconomic status | Low | 1.17 (1.11 to 1.23) | 1.33 (1.27 to 1.39) | 1.19 (1.05 to 1.35) |
| Average | 1.08 (1.03 to 1.14) | 1.13 (1.09 to 1.18) | 1.09 (0.96 to 1.22) | |
| High | Reference | Reference | Reference | |
| Urbanisation degree | Very high urban area | 0.94 (0.88 to 1.00) | 1.05 (0.99 to 1.10) | 0.89 (0.77 to 1.04) |
| High urban area | 0.97 (0.92 to 1.03) | 1.13 (1.08 to 1.19) | 0.94 (0.81 to 1.08) | |
| Moderate urban area | 0.98 (0.93 to 1.04) | 1.08 (1.02 to 1.13) | 0.97 (0.85 to 1.12) | |
| Minor urban area | 0.92 (0.87 to 0.98) | 1.01 (0.97 to 1.06) | 0.86 (0.74 to 0.99) | |
| Rural area | Reference | Reference | Reference | |
| Cattle density | Low | Reference | Reference | Reference |
| Medium | 1.00 (0.95 to 1.05) | 1.02 (0.98 to 1.06) | 1.05 (0.93 to 1.19) | |
| High | 1.03 (0.97 to 1.10) | 1.00 (0.95 to 1.05) | 1.03 (0.89 to 1.20) | |
| Goat density | Low | Reference | Reference | Reference |
| Medium | 1.01 (0.97 to 1.05) | 0.98 (0.95 to 1.02) | 0.98 (0.88 to 1.09) | |
| High | 0.94 (0.89 to 0.99) | 0.97 (0.93 to 1.02) | 0.99 (0.88 to 1.13) | |
| Sheep density | Low | Reference | Reference | Reference |
| Medium | 0.97 (0.92 to 1.01) | 0.95 (0.92 to 0.98) | 1.00 (0.92 to 1.14) | |
| High | 0.97 (0.93 to 1.02) | 0.92 (0.88 to 0.96) | 1.01 (0.89 to 1.10) |
Number of observations used: 312 420.
*Reference group included pregnancy outcomes in areas not affected by Q fever in 2008–2010 combined with outcomes in areas affected and unaffected by Q fever in the preoutbreak years of 2003–2004.
†Interaction term of interest, adjusted for confounders age of the mother, ethnic background, smoking, socioeconomic status, urbanisation degree, cattle density, goat density and sheep density.