The risk of venous thromboembolism associated with low oestrogen oral contraceptives

Abstract

SummaryThis study sought to quantify the risk of thromboembolic disease associated with low oestrogen oral contraceptives. The data source for the investigation was general practice medical records of 697 000 women in the United Kingdom over 12 months. Twenty-five per cent of the women were exposed to oral contraceptives during the study. Combined oral contraceptives with oestrogen doses between 30 and 35 /ig were used by 88-5 per cent of these. The incidence of thromboembolic disease amongst the exposed group was 3 0 per 10 000 women years. The incidence associated with pregnancy was 5-9 per 10 000 women years and that amongst women neither exposed to oral contraceptives nor pregnancy was 11 per 10 000 woman-years. The incidence rates in this study are of the same order as those found with low dose oral contraceptives in earlier investigations and confirm the fact that low dose oral contraceptives are relatively safer than their higher dose predecessors.