Table 2. Efficacy of VDBP to predict spontaneous labour onset (N = 141 women; 392 samples).

Prediction	3 d before onset	7 d before onset	14 d before onset
Samples (N)	≤3 days; N = 41	≤7 days; N = 71	≤14 days; N = 111
	>3 days; N = 351	>7 days; N = 321	>14 days; N = 281
Area under curve	0.974	0.943	0.934
95% confidence interval	0.958–0.989	0.921–0.966	0.912–0.956
P value	<0.001	<0.001	<0.001
Classification cut-off value	0.5	0.5	0.5
Sensitivity (%)	58.5	57.7	71.2
Specificity (%)	98.6	96.6	87.9
Positive Predictive Value (%)	82.8	78.8	69.9
Negative Predictive Value (%)	95.3	91.2	88.5