The aim of this study is to assess the impact of different protocols used for ovarian stimulation during in vitro fertilization procedures (IVF) on prothrombotic biomarkers (blood coagulation markers associated with thromboembolic events) in the units of reproductive medicine in two university hospitals (HUG, Geneva and CHUV, Lausanne).

HEMO-STIM is a prospective multicentric cohort study of subfertile women undergoing ART. It is an epidemiologic observational study. All women older than 18 years attending the reproductive medicine unit (UMREG, Geneva, HUG or UMR, Lausanne, CHUV) and undergoing an IVF have been and will be recruited consecutively and included. The type of stimulation protocol used is recorded.

All measurements (specific haemostasis test with a thrombin generation assay before and after adjunction of APC) that are part of the study will be performed in the HUG laboratories in order to limit inter-dosage variability.

The 1st blood test will be performed at inclusion in the absence of any hormonal treatment (T1). A 2nd blood test will be performed on the day of ovulation triggering (T2). A 3rd blood test will be performed 7 days after ovulation triggering (T3).

The comparison of different protocols has never been performed and data on the effect of antagonist protocols for IVF on haemostasis are lacking. The measurement of intermediate biomarkers of thromboembolic risk during different IVF stimulation protocols (agonists and antagonists) would allow the comparison of their thrombotic profile and to optimize the risk/benefit ratio during ART by prescribing protocols at lower vascular risk, in particular in women identified as being at risk for thromboembolic events.

Inclusion Criteria:

• Women older than 18 years
• Sub-fertile and undergoing IVF

Exclusion Criteria:

• >43 years old

Women will be recruited in reproductive unit from 2 hospitals (HUG, Geneva and CHUV, Lausanne) in Switzerland