Blackburn, Ruth, Linda Wijlaars, Katie Harron, Astrid Guttmann, and Ruth Gilbert. 2018. “Maternal Mortality of Women With Opioid-Use During Pregnancy in England: Investigating Bias in a Cohort of Linked Mother-Baby Hospital Records”. International Journal of Population Data Science 3 (4). https://doi.org/10.23889/ijpds.v3i4.895.