The VDBP concentration in the CVF significantly increased with advancing gestational age.

<p>The * indicates significance in the VDBP concentration in gestational groups ≤30–31 weeks' compared with CVF samples collected ≥36 weeks' gestation. The † indicates significance in VDBP concentration between samples collected at 36 and 37 weeks' gestation compared with samples collected at 40 and 41 weeks' gestation. Statistical significance was defined as <i>P</i><0.05 (2-way ANOVA). The box and whisker plots represent the median and interquartile range with the 5^th and 95^th centile range. Outliers are represented by open circles.</p

The effect of sexual intercourse and vaginal microbiology status on VDBP concentration.

<p>(A) Unprotected sexual intercourse within 48 h of CVF collection did not affect the VDBP concentration in women who delivered either term (<i>P</i> = 0.237) or preterm (<i>P</i> = 0.406, 2-way ANOVA). (B) The microbiology status of women with subsequent preterm or term labour did not affect the VDBP concentration. Within each labour group, VDBP was not significantly different between women with normal vaginal flora, Group B Streptococcus (GBS) colonisation, <i>Candida</i> spp. colonisation, <i>Ureaplasma</i> spp. colonisation, and women with mixed colonisation (Term: <i>P</i> = 0.478, Preterm: <i>P</i> = 0.557; 2-way ANOVA). The box and whisker plots represent the median and interquartile range with the 5^th and 95^th centile range. Outliers are represented by open circles.</p

Flow Diagram illustrating the pool of 221 women recruited in the two arms of the study.

<p>Eight subanalyses of VDBP expression in the CVF were performed and the number of samples utilised is indicated.</p

Demographic and clinical data of participants in the study (N = 221 women).

<p><i>Values are presented as mean ± SD</i></p

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

<p>Efficacy of VDBP to predict spontaneous labour onset (N = 141 women; 392 samples).</p

ROC curves of VDBP to predict labour onset within 3, 7 and 14 days.

<p>Subjects who provided two or more samples were included in the analysis (N = 392), with the subject entered as a categorical factor in the model. Area under the curves were 0.974 at ≤3 days; 0.943 at ≤7 days; and 0.934 at ≤14 days prior to spontaneous labour onset. Optimal predictive utility was obtained at ≤3 days from spontaneous labour.</p

The comparison of VDBP concentration between singleton and twin pregnancies.

<p>VDBP was not significantly different between singleton and twin gestation in-labour (<i>P</i> = 1.000), 0–7 days (<i>P</i> = 0.997), 8–14 days (<i>P</i> = 1.000), 15–21 days (<i>P</i> = 0.750), 22–28 days (<i>P</i> = 0.999), and >28 days (<i>P</i> = 1.000) before labour onset (2-way ANOVA). The box and whisker plot represents the median and interquartile range with the 5^th and 95^th centile range. Outliers are represented by open circles.</p

The VDBP concentration in the CVF significantly increased with approaching spontaneous term labour onset.

<p>The * indicates a significant difference in VDBP concentration in the CVF between the in-labour group and groups ≥4 days from labour. The † indicates a significant difference between the 0–3 day group versus groups ≥15 days from labour onset. The ‡ indicates a significant difference between the 4–7 day group versus groups ≥15 days from labour onset. The § indicates a significant difference between the 8–14 day group versus groups ≥29 days from labour onset. The ¤ indicates a significant difference between the 15–28 day group versus groups ≥29 days from labour onset. Statistical significance was defined as <i>P</i><0.05 (2-way ANOVA). The box and whisker plots represent the median and interquartile range with the 5^th and 95^th centile range. Outliers are represented by open circles.</p