How do contraceptives affect the menstrual cycle?

Certain contraceptives can affect the menstrual cycle. Two examples are oral contraceptive pills and intrauterine devices. Combined estrogen-progestin oral contraceptives (colloquially known as “the birth control pill”) externally regulate the menstrual cycle by providing sex hormones in the form of a pill and consequently suppressing the body’s production of hormones. This inhibition of internal hormone formation means that ovulation does not occur, thus preventing pregnancy.^[1] Some people find that oral contraceptives alleviate the symptoms of certain conditions, like dysmenorrhea and PCOS, but they may also have adverse effects.^[2] The FDA is a good resource for more information on oral contraceptives.

A intrauterine device (IUD) is a small device that is inserted into the uterus by a clinician to prevent pregnancies. IUDs are the most common form of long-acting, reversible birth control used worldwide.^[3] In the United States, there are two main types of IUDs, ones that contain copper and ones that release the hormone levonorgestrel (a form of progesterone). Because these devices work locally, they usually do not suppress the body’s hormone production, and the menstrual cycle continues. However, they can have short-term and long-term effects on menstrual-related symptoms in some people.

IUDs can increase cramping and bleeding and can cause unscheduled bleeding and spotting; this usually subsides within the first 6 months, but it can be severe and/or prolonged enough to cause discontinuation.^[4][5] Conversely, in the long term, they can cause amenorrhea and lighter bleeding and can even reduce pelvic pain and dysmenorrhea.^[6][7][8]

It is important to speak with a clinician when weighing the risks and benefits of different contraceptives because the choice is highly individualized.