Table 2.

Cohort studies of oral contraceptives and risk of venous thromboembolism

Author	Study type	Setting	Study period	Study population	Assessment of exposure	Method of ascertainment	Firm diagnosis	Inclusion criteria	Control factors
Jick2	Cohort study	General practices in United Kingdom (General Practice Research Database)	Jan 1991-1994	238 130 women who were current oral contraceptive users	Information from medical records	Computer records	64%	Women without a history of venous thromboembolism, stroke, acute myocardial infarction, cancer, epilepsy, diabetes, treated hypertension, hyperlipidaemia, and cystic fibrosis	Age and calendar time
Farmer5	Cohort study	General practices in United Kingdom (MediPlus database)	Sep 1991–Sep 1995	491 908 women who were current oral contraceptive users	Information from medical records	Recorded diagnosis of deep vein thrombosis or pulmonary embolus and treatment with anticoagulant	?	Women born between 1941 and 1981, without a previous episode of venous thromboembolism, trauma, or surgery within past 3 months, or were within 3 months of delivery or termination of pregnancy, or had been prescribed emergency oral contraceptives within 4 weeks of the event	Age
Herings10	Cohort study	Data were obtained from the PHARMO system, which includes information of hospital admissions and drug-dispensing records for all residents of 8 Dutch cities	1986-95	All female residents of 8 Dutch cities (about 450 000)	Information from the PHARMO system	Patient's hospital discharge records	?	Women aged 15-49 years, who had ever used an oral contraceptive during 1986-95, without a history of venous thromboembolism, oral anticoagulants, depots hormone preparations, cardiovascular drugs, emergency contraception, or hospital admission for any reason in the 2 months before start of oral contraceptives	Year and age