Venous thrombosis during assisted reproduction: novel risk reduction strategies.

Ovarian hyperstimulation syndrome (OHSS) affects 5% of IVF cycles and incurs a 100-fold increase in risk of venous thrombosis over natural conceptions. Identification of women at risk of OHSS can be achieved using antral follicle count (AFC) and anti-Müllerian hormone (AMH). For those women with a high AFC or AMH combining a GnRH antagonist with a conventional hCG trigger will reduce the risk of OHSS and still allow a fresh transfer to occur. Complete abolition of OHSS is however now a reality by avoiding exposure to exogenous hCG. This can be achieved by segmentation of the IVF cycle using a GnRH agonist for final oocyte maturation and then freezing all oocytes or embryos with subsequent replacement of a single embryo in the context of a frozen embryo transfer. This novel approach will ensure a VTE risk equivalent to natural conception and can be combined with conventional thromboprophylaxis strategies.