Design and study population
This was a descriptive, retrospective, population-based study looking at the outcomes of new pregnancies in mothers with previous complete uterine rupture. Data were extracted from all births in Norway registered from 1967-2011 (N=2 455 797). Two registries were used: the Medical Birth Registry of Norway (MBRN) and the Patient Administration System (PAS). The MBRN contains information on all births in Norway after 16 weeks of gestation. Midwives attending a birth fill out and send a standardized MBRN form within 7 days after delivery. The PAS is a local registry at each maternity unit that maintains records of all inpatient diagnoses. All ruptures were identified using international diagnostic codes. In the MBRN, the internal code for uterine rupture was 71 prior to 1999; from 1999 to the present, the diagnostic codes are O710 and O711 based on the 10th revision of the International Classification of Diseases (ICD).8In the PAS, uterine rupture was identified by the ICD8 code (1967–1978),9ICD9 codes 6650 and 6651 (1979–1998),10and ICD10 codes O710 and O711 (1999–present).8These codes do not specify the rupture type (complete or partial), which was identified in the medical records. Complete rupture was defined as the rupture of all uterine wall layers, including the serosa and amniotic membranes, and partial rupture as rupture of the uterine wall, sparing the serosa or membranes. All births associated with a uterine rupture were identified by the first author, who visited maternity units in Norway and reviewed maternal medical records. Those with complete uterine ruptures were followed (n=274).
The study population was mothers with new pregnancies and child births after previous complete uterine rupture (n= 72). We studied the characteristics of previous complete ruptures and the rate of repeat ruptures and outcomes of these pregnancies.
The Regional Ethics Committee (2010/1609–4) and the Data Inspectorate of Norway approved the study. The South-Eastern Norway Regional Health Authority funded the study of uterine rupture as a post-PhD project for the lead author.