Research CMAJ, February 2, 2016, 188(2) E37Abstract Database 6 using the maternal personal health number to combine information on maternal characteristics and obstetric service outcomes. This registry is a quality-controlled population database containing abstracted medical chart information from more than 99% of deliveries in the province. A recent validation study showed high validity of many variables in this analysis. 7 The Discharge Abstract Database has been previously validated for perinatal data. 8 Using the maternal personal health number, we linked these data to the First Nations Client File, which is a cohort of First Nations people who are found in Aboriginal Affairs and Northern Development Canada's Indian Registry System, and their descendants who may be eligible to register. 9 The last linkage was to a geographic database that encoded the distance between the centre of the maternal residential postal code and the closest hospital with planned obstetric services, according to highway networks, in kilometres. This database also classified maternal postal code as either urban or rural (Appendix 1, available at www.cmaj.ca/ lookup/suppl/doi:10.1503/cmaj.150223/-/DC1).The British Columbia Vital Statistics Agency, British Columbia Ministry of Health, Perinatal Services BC, and the Data and Information Planning Committee (which provides stewardship over the First Nations Client File) approved access to and use of the data facilitated by Population Data British Columbia for this study. The study was approved by the University of British Columbia and British Columbia Children's and Women's Hospital research ethics boards. This project follows the Canadian Institutes of Health Research guidelines for research involving Aboriginal people 10 and is carried out in collaboration with the Maternal/Child Health Group of the First Nations Health Authority.
Outcome measuresNo universally agreed upon indicators of quality obstetric care currently exist. 11 Because our interest was in exploring differences in care processes, we identified process indicators that are aligned with best practice guidelines set by the Society of Obstetricians and Gynaecologists of Canada and that reflect services provided as part of standard care.We identified the following indicators of care: group B streptococcus testing and antibiotic use by those women with positive test results among deliveries at or beyond 37 weeks' gestation; 12 at least 4 primary care antenatal visits in pregnancies in which delivery occurred at or beyond 39 weeks' gestation (although there is no optimal number of visits, the World Health Organization recommends that women have at least 4 visits during pregnancy); 13 ultrasonography before 20 weeks' gestation (the Society of Obstetricians and Gynaecologists of Canada recommends "pregnant women should be offered a routine second trimester ultrasound" and has recently stated that, ideally, all women should be offered first-trimester ultrasonography for pregnancy dating); 14,15 medical induction of labour a...