Table 1 Univariate logistic regression to predict preterm delivery within 14 days after the first examination and before 34 weeksʼ gestation.

	Delivery within 14 days			Delivery before 34 wks
	OR	95 % CI	p	OR	95 % CI	p
Maternal age (yrs)	0.990	0.910–1.077	0.526	1.022	0.954–1.095	0.535
Nullipara (n)	1			1
Previous preterm delivery < 37 wks (n)	3.459	0.986–12.137	0.053	1.257	0.343–4.612	0.730
Previous term but no preterm delivery (n)	0.925	0.277–3.088	0.899	0.848	0.339–2.125	0.726
Weight (kg)	0.999	0.963–1.037	0.959	1.001	0.972–1.031	0.930
No cigarette smoking	1
Cigarette smoking	1.004	0.126–8.025	0.997	1.693	0.217–13.243	0.616
C-reactive protein (mg/dl)	1.133	0.775–1.655	0.520	1.048	0.732–1.501	0.796
White blood cell count (n/µl)	1.000	1.000–1.000	0.567	1.000	1.000–1.000	0.804
No bacterial vaginosis	1
Bacterial vaginosis	0.604	0.165–2.213	0.447	0.748	0.243–2.301	0.613
Gestational age at first Cx length measurement (wks)	1.205	0.933–1.462	0.060	0.887	0.779–1.010	0.070
First Cx measurement (mm)	0.900	0.837–0.968	<0.005	0.884	0.831–0.940	<0.0 001
Gestational age at second Cx length meaurement (wks)	1.040	0.966–1.120	0.295	1.036	0.968–1.109	0.313
Second Cx measurement (mm)	0.868	0.808–0.933	<0.0 001	0.865	0.815–0.919	<0.0 001
Difference between first and second Cx measurement (mm)	0.843	0.753–0.944	0.003	0.887	0.805–0.978	0.016