This study compares the risks of short- and long-term use of NOMAC-E2 (containing a fixed dose of nomegestrol acetate and estradiol) compared with levonorgestrel-containing combined oral contraceptives (COC-LNG) in a study population representative of the actual users of the individual preparations.

NOMAC-E2 is a novel monophasic oral contraceptive containing a fixed dose of nomegestrol acetate (2.5mg) and 17ß-estradiol (1.5mg) which is taken for 24 days followed by 4 days of placebo. The most relevant adverse clinical outcome that has been linked to the use of COCs is venous thromboembolism (VTE). Data from randomized clinical trials did not show any serious health concerns for NOMAC-E2. However, the statistical power to detect rare adverse events is limited in these studies.

PRO-E2 is a large, prospective, controlled, long-term active surveillance study to investigate the safety of NOMAC-E2 with regard to the outcomes of interest. This study follows the European Active Surveillance (EURAS) design methodology with some modifications due to country- and product-specific characteristics. The outcomes of interest will be validated via the attending physicians. A multi-faceted follow-up procedure will ensure a low loss to follow-up rate. This study will involve women from Europe and Australia who will be followed for up to 2 years. Data analysis will include multivariable techniques such as Cox regression.

Inclusion Criteria:

• First ever user of a COC ("starter")
• User who restarts hormonal contraceptive use with a COC (same COC as before or a new COC) after an intake break of at least two months ("restarters")
• Women willing to participate in the active surveillance

Exclusion Criteria:

- Women who do not understand the major aspects of the study

Women using oral contraceptives