Inter- and intra-observer variability in cervical measurement by ultrasound in the first and second trimesters of pregnancy: does it matter?

ABSTRACT

OBJECTIVES: The aim of this study was to evaluate the inter- and intra-observer variabilities in the cervical length (CL) measurement by transvaginal ultrasound (TVU) in the first and second trimesters of pregnancy. MATERIALS AND METHODS: A total of 55 singleton pregnant women were evaluated in the first or second ultrasound. Each patient was blindly evaluated by three of the four observers who performed three measurements each. RESULTS: In the first and second trimesters, patients were evaluated at 12.3 weeks (mean) and 21.3 weeks (mean), respectively. The intra-class correlation coefficients (ICC) between observers in the first and second trimesters were 0.76 and 0.72, respectively, and the ICCs within observers were 0.889 and 0.899, respectively. In both trimesters, the main source of variance was the patient and the second source of variance was the interaction, Patient×Observer (12.0% and 13.5%, respectively). The observer and measurement explained a small proportion of variance in both trimesters (1.4% and 0.4%, respectively in the 1st trimester, and 3.3% and 0%, respectively in the 2nd trimester). The residual variances were 10.6% and 11.2%, and the standard errors of measurement were 1.78 mm and 1.82 mm for the first and second trimesters, respectively. CONCLUSIONS: TVU is a reliable and reproducible method by which to predict preterm birth in both the first and second trimesters.