P39.17: Intraobserver and interobserver reproducibility of transvaginal ultrasonographic measurements of cervical length at 16-18 weeks, 20-22 weeks and 37-39 weeks

To determine intraobserver and interobserver reproducibility of transvaginal ultrasonographic measurements of cervical length at 16–18 weeks, 20–22 weeks and 37–39 weeks, and to compare its reproducibility among these three gestational periods. Cervical length was measured three times by the same experienced examiner in each of thirty-eight women at 16–18 weeks, 43 women at 20–22 weeks and 43 women at 37–39 weeks. A second experienced examiner then repeated the measurements. Intraobserver repeatability was expressed as the difference between the highest and lowest measurement values obtained by the same observer and as intraclass correlation coefficient (intra-CC). Interobserver agreement was expressed as the difference between the means of the three measurements of each observer and as interclass correlation coefficient (inter-CC). Intra-CC for cervical length measurements at 16–18 weeks, 20–22 weeks and 37–39 weeks were 0.98, 0.97 and 0.99 for observer 1, and 0.98, 0.97 and 0.98 for observer 2, respectively. 2) Inter-CC for cervical length measurements at 16–18 weeks, 20–22 weeks and 37–39 weeks were 0.89, 0.79 and 0.95, respectively. 3) The intraobserver repeatability and interobserver agreement for cervical length measurements were not significantly different among at 16–18 weeks, 20–22 weeks and 37–39 weeks. The intra- and inter-observer reproducibility of transvaginal ultrasonographic measurements of cervical length at 16–18 weeks, 20–22 weeks and 37–39 weeks were highly reliable when experienced examiners performed the measurements under standardized condition. Gestational age at cervical length measurement did not influence its reproducibility.