- Dustin J Costescu, contraceptive advice research and education fellow1,
- Ashley Waddington, contraceptive advice research and education fellow1
- 1Department of Obstetrics and Gynaecology, Queen’s University, Kingston, ON, Canada K7L 2V7
Helmerhorst and Rosendaal’s recommendation that women prescribed oral contraceptives should receive levonorgestrel and 30 µg of ethinylestradiol is based on the observation that thrombosis risk is related to ethinylestradiol amount and progestogen type.1 Although interesting, this strategy is not adequately evidence based.
Retrospective database studies of contraception and thrombosis are often cited because they are inexpensive and can rapidly amass large datasets. Unfortunately, conclusions are …