From preventing pregnancy to acne moderation, helping with endometriosis pain to managing intense period symptoms, birth control does it all. But, how does it work? If you’ve ever found yourself wondering what exactly your birth control is doing to your body, then this article is for you. Today, Binto unpacks how your hormonal birth control works.
Let’s start with the pill.
The hormonal birth control pill is the most commonly prescribed method of birth control in the US. The most common pill is the combined hormonal pill which contains estrogen and progestin, the synthetic form of progesterone. These hormones work together to prevent pregnancy and moderate your menstrual cycle.
The progestin in the pill prevents follicular development, which prevents ovulation, thus preventing pregnancy. Normally, when an egg is released your estrogen levels fall and your progesterone levels begin to rise. These return to normal when the egg is not fertilized, and your cycle continues. The progestin in the pill keeps your pituitary gland thinking you have just ovulated, so it does not send the signals to try and grow another egg. It also thickens the mucus of your cervix which makes it harder for sperm to reach your fallopian tubes. With no egg traveling down the fallopian tubes, and sperm being blocked from swimming up, getting pregnant becomes a lot less likely. While the estrogen component of the pill also contributes to preventing ovulation, its main job is regulating the uterine lining to help control menstrual bleeding.
You have to take the pill daily on a regular schedule for it be maximally effective. Planned Parenthood estimates that when taken correctly and regularly, the birth control pill is 91% effective at preventing pregnancy.
Moving on to other forms of hormonal birth control…
Like the pill, the patch contains estrogen and progestin which are absorbed through your skin. Again, similar to the pill, these hormones stop ovulation from happening while also thickening your cervical mucus. The patch has to be replaced weekly for three weeks at a time before a weeklong break where you get your period. You can wear the patch on your upper arm, stomach, butt, or back. For it to work properly, you have to be diligent about putting on a new patch each week. According to Planned Parenthood, when used correctly and changed on time, the birth control patch is about 91% effective.
Yet another method of delivering estrogen and progestin, the birth control ring is a small, flexible ring worn inside your vagina. It differs from the pill and the patch in that the estrogen and progestin are absorbed through the mucus membrane in your vagina, but they work in the same way to prevent ovulation and thicken your cervical mucus. The ring is worn for three weeks at a time before a weeklong break where you get your period, and like the patch, you have to remember to replace it on time. Planned Parenthood estimates that correct use of this birth control method is about 91% effective at preventing pregnancy.
The rod implant is a progestin-only method, meaning it does not contain estrogen. It works similarly to the other methods, inhibiting ovulation to prevent pregnancy as described above. Typically inserted into your upper arm, these implants are a reversible form of birth control that can prevent pregnancy for up to 3-5 years before being replaced. Planned Parenthood estimates that the implant is more than 99% effective at preventing pregnancy.
The IUD is another reversible, long-term, progestin-only birth control method. It is a small device that’s implanted in your uterus to prevent pregnancy. There are three types of IUDs commercially available in the US: the Mirena and Skyla are progestin-only hormonal implants, and the copper IUD, Paragard, is non-hormonal. The Skyla is the smallest IUD, effective for 3 years of use, where the Mirena is a little larger and works for up to 5 years.
IUDs work a little differently than the pill. For a pregnancy to happen, a fertilized egg must implant in the endometrium, or inner lining of the uterus, so the progestin in hormonal IUDs works to create an anti-implantation effect by suppressing it. It also thickens the cervical mucus to block sperm from reaching the fallopian tubes in the first place. Lastly, the progestin inhibits tubal motility, which is the muscle contraction within the fallopian tubes that brings the sperm and egg together. So, while you still ovulate with a hormonal IUD, the suppression of your endometrium typically leads to reduced or eliminated period symptoms, and the process of conception is blocked at multiple junctures.
Since copper IUDs are not hormonal, they function a little differently. The copper ions in the IUD create an environment that is toxic to sperm, but not to you. This kills any sperm that enters your uterus, as well as making the endometrium non-viable for sperm. Since it is a non-hormonal method, people who have a copper IUD still experience their menstrual periods, but they do not experience any additional hormonal side effects. Once inserted, the device can prevent pregnancy for up to 10 years.
IUDs are a highly effective form of reversible long-term contraception. According to Planned Parenthood, IUDs are more than 99% effective at preventing pregnancy.
While the progestin and estrogen in hormonal birth control will prevent pregnancy when used properly, it is important to note that none of these methods prevent STDs. The only birth control method that can stop you from contracting a sexually transmitted disease or infection is using a condom. If you are trying to effectively protect yourself from pregnancy and STDs, it is a good idea to pair your hormonal birth control method with regular condom use.