The cohort was then coded as to whether they had hypertension or remained normotensive in their pregnancy. The entire cohort was linked utilising identifying variable by the Centre for health record linkage to the NSW Registry of Births , Death and Marriages (Death data) and to the ABS cause of death database. The linkage period was between the years 1980-2009. Cardiovascular death was identified by the use of ICD-9-AM codes (390-495) and ICD-10-AM codes (100-199) depending upon the years of death. The sub-set of the women who had detailed pregnancy data collected was maintained on a separte dataset. This dataset also provided information on the severity of the disease.