Table 2.

Cox Proportional Hazard Regression Analysis of Spontaneous Preterm Birth Prior to 37 Weeks

Parameter	Adjusted Hazard Ratio	95% Confidence Interval	p-value
Progesterone Treatment (yes)	0.501	0.283–0.729	0.001
Cervical Length (mm)	0.552	0.332–0.924	0.023
Prior Preterm Births (yes)	1.782	1.155–2.786	0.011
Gestational Age at Diagnosis (week)	0.989	0.973–0.994	0.024
Maternal Age (year)	1.051	1.012–1.086	0.008

The unadjusted hazard ratio for spontaneous preterm birth prior to 37 weeks after progesterone treatment was 0.52; CI 95% 0.32–0.84; p=0.008. B=0.650, SE(β)=0.244, Wald=7.099. In this model, adjustments were performed for maternal age, history of preterm births, cervical length, and gestational age at diagnosis.