Table 2.

Gestational age parameters for Danish pregnant women according to antibodies against C.burnetii, immunofluorescence antibody test (IFA)

	IFA positive for C. burnetii antibodies (n = 169)	IFA negative for C. burnetii antibodies (n = 687)	Measures of association
			Crude	Adjusted
Spontaneous abortion < 22 weeks (n = 8)	2 (1.2%)	6 (0.9%)	OR: 1.4	1.5 (95% CI: 0.3–7.6)*
Preterm birth (< week 37) (n = 41)	3 (1.8%)	38 (5.5%)	OR: 0.3	OR: 0.4 (95% CI: 0.1–1.1)**
Gestational age (>week 36 + 6) (n = 806****) Median gestational age (interquartile range)	40 weeks 3 days (39 w, 3d; 41 w,1 d)	40 w, 2 days (39w, 3d; 41w,1d)	Mean difference in days*** 0.91 days	1.2 days (−0.4– +2.7)**

*adjusted for age **adjusted for smoking, age and gravidity *** babies of IFA positive mothers were older **** of which 163 were seropositive and 643 seronegative.