Accuracy and intraobserver variability of simulated cervical dilatation measurements

OBJECTIVE: Our purpose was to assess the accuracy and intraobserver variability of clinical cervical diameter measurements among obstetric health care providers. STUDY DESIGN: Polyvinyl chloride pipes 1 to 10 cm in diameter were mounted in cardboard boxes and used to simulate cervical examinations. The boxes were designed so that the examiner had to rely solely on proprioception to determine the inner diameter. RESULTS: A total of 1574 simulated cervical diameter measurements were obtained from 102 different examiners in a two-part study. The overall accuracy for determining the exact diameter was 56.3%, which improved to 89.5% when an error of ±1 cm was allowed. Intraobserver variability for a given diameter measurement was 52.1%, which decreased to 10.5% when an error of ±1 cm was allowed. CONCLUSIONS: Cervical diameter measurements obtained by digital examination are precise when an error of ±1 cm is allowed for. Intraobserver variability is >50% and is an important consideration when evaluating dysfunctional labor.