Oral contraception and venous thromboembolism. A New Zealand perspective.

Several recent case control studies have shown an excess rate of venous thromboembolism in women using third generation progestogen-containing combined contraceptive pills compared to second generation combined contraceptive pills. This excess is about 1 in 10,000 women per year of use. It is likely that second and third generation pills have been preferentially prescribed to users who have varying susceptibility to venous thromboembolism and that this may account for at least part of the observed differences. In practice, it is essential that all women using combined oral contraceptive pills have a thorough history taken to exclude any contraindications or risk factors. Each client should be counselled about the risks and benefits of oral contraception. In New Zealand, the Ministry of Health has recommended that prescribers for women starting a contraceptive pill for the first time should consider a pill that does not contain a third generation progestogen. Women already receiving a third generation pill may elect to continue that pill after the differential rates of venous thromboembolism have been discussed.