EURAS is a multi-national, controlled, prospective, post-marketing, non-intervention cohort study of new users of drospirenone/ethinylestradiol (DRSP/EE), levonorgestrel/ethinylestradiol (LNG/EE) and other oral contraceptives (OCs) under routine conditions of medical practice in seven European countries. Baseline survey and semiannual, active follow-up are based on postal questionnaires, with validation of reported events by the women's treating physicians. A multifaceted 4-level follow-up procedure will be established to ensure low loss to follow-up rates. The objective of the study is the investigation of the incidence of rare serious adverse events associated with the use of new and established OCs, and specifically the incidence of thromboembolic events.

Active surveillance using valid epidemiologic study designs is desirable for any new product, because adverse effects may occur that have not yet been identified in pre-marketing studies.

The EURAS study investigates the safety of oral contraceptives with a large cohort of women attending offices of prescribing physicians. Its primary objective will be to compare incidence rates of adverse events in users of so-called new OCs and users of other OCs. The study is conducted as a phase IV commitment to the European Drug Authorities.

The combined cohort will include 50,000 to 60,000 women recruited by a selected set of physicians in six European countries. A total of more than 1,500,000 cycles are expected to be observed during the field work which will start early in 2001 and end early in 2006.

The participating women will undergo a baseline survey using a self administered questionnaire to describe the baseline risk. Every six months they will fill out a questionnaire in which they will record complaints and events during the use of the prescribed OC which will be validated. A multifaceted 4-level follow-up procedure will be established to ensure low loss to follow-up rates.

Based on experience obtained in previous OC studies complex sources of bias and confounding are expected. Thus, multivariate methods such as Cox regression will be used to adjust for confounding. Regarding the impact of the results on public health, the main emphasis will be on the absolute risk estimates.

Inclusion Criteria:

• Women starting OC use or women switching OCs
• Women willing to participate in the active surveillance for several years

Exclusion Criteria:

• Women who have contraindications for OC use

Women prescribed hormonal contraceptives

Between 1.5 and 5 years

This is an observational study. The possibility of bias and residual confounding cannot be entirely eliminated.