Sidney 1998.

Methods	Case‐control study
Participants	271 cases/993 controls Aged 18 to 44 years
Interventions	Combined oral contraception: current use, past use, none use, norethindrone, norgestrel, < 50 µg oestrogen, ≥ 50 µg oestrogen
Outcomes	Myocardial infarction Events: current use 12/87, past use 214/769, none use 41/135, norethindrone 8/52, norgestrel 3/24, < 50 µg oestrogen 9/78, > 50 µg oestrogen 2/5
Notes	USA
Risk of bias
Bias	Authors' judgement	Support for judgement
Exposure ascertainment	High risk	COC use not objectively confirmed.
Outcome assessment	High risk	Myocardial infarction not 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.