To understand what progesterone is and how it works, it’s important we first understand the role of hormones more generally. Hormones are produced in glands and, in simple terms, work as a sort of messenger for the body.
Hormones are made out of a chemical substance which travels through the tissue in order to reach different parts of the body. When a hormone gets to its destination, the message is ‘delivered’ and this starts a process. For example, the sex hormone, estrogen, is produced in the ovaries and is important in triggering different phases in the menstrual cycle.
Progesterone is a sex hormone found in both men and women. As with estrogen, progesterone plays a key role in female reproductive health and, in particular, is important in the later stages of the menstrual cycle and during pregnancy.
Progesterone is a big player in the latter phase of the menstrual cycle (the luteal phase). This is because progesterone is the hormone that keeps the uterus lining thick. If an egg is fertilized, then progesterone levels stay steady and this prevents uterine contractions and shedding.
If a woman gets pregnant, progesterone levels stay stable in order to stop the cycle from ending and her period starting. Progesterone is also essential to the body’s function during pregnancy, as it also helps get the breasts ready for milk production. Alternatively, if an egg is not fertilized, then progesterone levels decline, the uterus lining sheds (a woman gets her period), and a new cycle begins.
Hormonal birth control works by using synthetic estrogen and/or progesterone to keep hormones steady. Without a surge or decline in hormones, different phases of the menstrual cycle cannot be triggered. For example, a steady level of progesterone prevents ovulation from taking place. So if the levels are kept stable, no egg will be released and so cannot be fertilized.
There are several types of hormonal birth control which only use progesterone (and not estrogen), these include the mini pill (or the progesterone-only pill) and the contraceptive injection. These types of birth control can work well for women who cannot use birth control with synthetic estrogen but are still looking for hormonal birth control options.
If you are searching for a non-hormonal birth control method that adapts to your unique cycle, then the Natural Cycles birth control app might be what you’re looking for. The intelligent app works by analyzing daily basal body temperature readings and identifying your fertile window. This means you will know where you are in your cycle and can use condoms or abstain from sex on fertile days to prevent pregnancy.