I have a grad student whose research involves the prevalence and severity of back pain during pregnancy. We can find chronic pain / chronic conditions (Health Indicators, CCHS, etc.), but is there a combination of resources that will allow her to make that correlation?
Have you consulted PHAC? StatCan conducted the Maternity Experiences Survey (MES) as part of the Canadian Perinatal Surveillance System of the Public Health Agency of Canada who sponsored the survey.
They have results on their website:
The Canadian Maternity Experiences Survey
I found tables that reported back pain in postpartum, not during pregnancy unfortunately.
Maternal and Infant Health