Heinemann 1998.

Methods	Case‐control study
Participants	220 cases/775 controls Ages 16 to 44
Interventions	Combined oral contraception: current and none use, 1st generation, 2nd generation, 3rd generation
Outcomes	Ischemic stroke Events during: current use 124/182, none use 96/257, 1st generation 15/23, 2nd generation 58/97, 3rd generation 45/54
Notes	UK, Germany, France, Switzerland and Austria
Risk of bias
Bias	Authors' judgement	Support for judgement
Exposure ascertainment	Low risk	COC use objectively confirmed.
Outcome assessment	Low risk	Ischemic stroke objectively confirmed.
Follow‐up	Unclear risk	Not applicable as this was a case‐control study.
Source population	Low risk	Controls from the same source population as the cases.