Third generation P-pills and deep venous thrombosis
Olsen, J.
Ugeskrift for Laeger 158(13): 1843-1845
1996
ISSN/ISBN: 0041-5782 PMID: 8650762 Document Number: 468371
The World Health Organization (WHO) conducted a large study in 1995 to find out whether modern low-dose oral contraceptives (OCs) have the same side effects as those found earlier with older preparations. The investigation was carried out in 21 centers in 17 countries, with the first studies investigating deep venous thrombosis and pulmonary embolism. Women 20-24 years old who were hospitalized with either of these conditions were recruited during 1989-93. The case diagnoses were performed by means of venography, scanning, radioactive isotopes, or clinical signs. For each case three age-matched hospital controls were chosen without OC-related diagnosis of their conditions. A total of 1011 women with deep venous thrombosis and 206 with pulmonary embolism were included, of whom 42% and 25%, respectively, were diagnosed as certain cases. OC use increased the risk of deep venous thrombosis and pulmonary embolism by a factor of 4.2, and this risk seemed to be associated with the present use of OCs without any indication of increased risk because of long-term use. A second WHO study carried out in 1995 revealed that the risk was higher with these new third generation OCs than with traditional OCs. 137 cases and 203 controls were recruited who used levonorgestrel, and their odds ratio for deep venous thrombosis and pulmonary embolism was 3.5. 35 cases and 28 controls used desogestrel, and their odds ratio for these conditions was 9.1. 36 cases and 28 controls used gestodene with an odds ratio of 9.1. The risk of these third generation OCs was 2.6 times higher than the risk associated with the second generation OCs. These studies caused a debate because of the economic interests involved in these OCs. The statistical association still has to be confirmed because of possible confounding by indication, since these third generation OCs were considered as posing less risk compared to traditional OCs. The indications were based on this assumption, consequently women with higher cardiovascular risk took them.