Combined hormonal contraception (CHC), or combined birth control, is a form of hormonal contraception which combines both an estrogen and a progestogen in varying formulations. The different types available include the pill, the patch and the vaginal ring, which are all widely available, and an injection, which is available in only some countries. They work by mainly suppressing luteinising hormone (LH) and follicle-stimulating hormone (FSH) and in turn preventing ovulation.
