The study revealed the risk of developing venous thromboembolisms from various types of synthetic hormones, providing important information going beyond just progesterone-only or combined.

The sex hormones estrogen and progesterone control the menstrual cycle. Estrogen and progesterone levels dip at the start of your period. When your period ends, estrogen levels start increasing again.

Although high-dose progesterone-derived progestins are used in European countries with a real contraceptive effect it has not been evaluated in large studies and the Pearl index is not known.