Validation of data in the Medical Birth Registry of Norway on delivery after a previous cesarean section

Introduction Trial of labor (TOL) is an option in most deliveries after a previous cesarean section (CS). The Medical Birth Registry of Norway (MBRN) has received compulsory notification of all deliveries in the country since 1967, including data that could identify TOL in epidemiologic research. The objective of this study was to validate MBRN data for identification of TOL deliveries after a previous cesarean section (CS). Material and methods The MBRN provided a random national sample of 500 birth order two deliveries during 1989–2012 in women with a registered birth order one CS delivery. The reporting maternity units were asked to complete a questionnaire on data items in both deliveries, using hospital record data as the gold standard. Results Completed questionnaires were returned for 477 women (95.5%) with data on both deliveries. An algorithm to identify TOL using MBRN data from the birth order two delivery had a positive predictive value of 93.2%, a negative predictive value of 93.5%, a sensitivity of 96.1%, and a specificity of 88.8%. Validity of MBRN data on mode and onset of delivery, CS subtype, and planned mode of delivery is also reported. Conclusions MBRN data on planned and actual mode of delivery, CS subtype, and the algorithm to identify TOL in deliveries after a previous CS had satisfactory quality for a registry‐based study of TOL.