27th June 2023

Progesterone-only methods

Methods include the once-daily pill (POP), the injection (which is given either 8- or 13-weekly depending on type) and the long-acting implant, which can be changed every three years. All methods work similarly to prevent conception in multiple ways, including increasing the thickness of cervical mucus and making the endometrium hostile to implantation. Additionally, ovulation is suppressed by preventing the midcycle peaks of LH and FSH.

All methods can be used while breastfeeding (injectable is UKMEC 2), can be used in patients with a previous venous thrombosis (UKMEC 2) and are safe in patients with a BMI >35. There is evidence to suggest that the POP reduces dysmenorrhea and mid-cycle ovulation pain.

All methods are associated with unscheduled menstrual bleeding, and the injectable can have up to a 1-year delay in fertility returning to normal once stopped. The injectable is also associated with weight gain and loss of bone mineral density, although this is usually recovered after discontinuation.