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Reproducibility of cervical length measurement throughout pregnancy
Athena P Souka1, Athanasios Pilalis1
1Fetal Medicine Unit, Attikon University Hospital, Athens, Greece.
Objectives:
To assess the intra- and interobserver variability of cervical length (CL) measurement in the three trimesters of pregnancy.
Methods:
Prospective observational study. Transvaginal CL measurement was performed by two operators ignorant of each other's results. Two methods of measurement were assessed: the straight line method (SL = from internal to external cervical os along the endocervical mucosa) and the two-line method (TL = the sum of two lines following the curvature of the endocervical canal).
Results:
There were 236 sets of CL measurements of which 96 (40.7%), 73 (30.5%), and 67 (28.8%) were performed in the first, second, and third trimesters of pregnancy, respectively. Intra- and interobserver variability was excellent for both methods (ICC 0.90) and was not influenced by gestational age. Mean difference was 1 mm (LOA -4 to -3 mm) for the same examiner and 1 mm as well between examiners (LOA -5 to -7 mm). Mean CL was slightly longer for the 2-L method (33 mm, SD = 5.2) compared to the SL method (31.4 mm, SD = 4.9). There was significantly more bias in the difference between methods the longer the CL measurement was (p <.001).
Conclusions:
CL measurement shows excellent intra- and interobserver variability across gestation and the variability of the measurement is not influenced by gestational age or CL length for either method. The TL method produces slightly longer values.
