27th June 2023

Combined Hormonal Contraceptives (CHCs)

CHCs contain oestrogen and progesterone, which works on the hypothalamo-pituitary axis to reduce the production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), thereby inhibiting ovulation. Additionally, CHCs affect the cervical mucus and endometrium to give a hostile environment for implantation.

Three CHC methods are available: a once-daily pill, a 7-day transdermal patch, and a 21-day vaginal ring. All the methods can be used ‘off label’ without a contraception-free interval, which prevents the withdrawal bleed. The efficacy of all three methods is similar, with in-practice use showing a 9% failure rate. Before starting a CHC, the UKMEC guidance should be carefully consulted with regards to smoking, age, obesity, and migraines with aura.