Study Design and Data Sources
This population-based cohort study comprised all singleton hospital livebirths and stillbirths in Ontario, April 1, 2006 to March 31, 2014. We obtained pregnancy and neonatal outcomes from the Better Outcomes Registry & Network (BORN) Ontario and Niday Legacy data sets (www.bornontario.ca/en/data/data-dictionary/legacy-datasets/). BORN captures more than 99% of hospital births in the province and has been previously validated for completeness and accuracy.18 Excluded were pregnancies that resulted in termination, or a gestational age below 20 complete weeks. Analyses were restricted to women aged 18 to 60 years. Maternal demographics and pre-existing health conditions were obtained from the Canadian Institute for Health Information Discharge Abstract Database (CIHI DAD), National Ambulatory Care Reporting System (NACRS), Ontario Health Insurance Plan Claims Database (OHIP), Registered Persons Database (RPDB), Postal Code Conversion File (PCCF), Linked Delivering Mothers and Newborns (MOMBABY), Ontario Hypertension Dataset (HYPER), Ontario Diabetes Dataset (ODD), and the Immigration, Refugees and Citizenship Canada Permanent Resident (IRCC-PR) database – all existing linked datasets at ICES (www.ices.on.ca). ICES is an independent, non-profit research institute funded by an annual grant from the Ontario Ministry of Health (MOH) and the Ministry of Long-Term Care (MLTC). As a prescribed entity under Ontario’s privacy legislation, ICES is authorized to collect and use health care data for the purposes of health system analysis, evaluation and decision support. Secure access to these data is governed by policies and procedures that are approved by the Information and Privacy Commissioner of Ontario.