How Do Birth Control Pills Work
According to a recent 2021 study, 25% of women ages 15 - 44 that use contraception report that they chose oral pills as their method. Many women are administered the birth control pill to not only prevent pregnancy but also to regulate periods, treat endometriosis, and reduce acne. It is important to ask how do birth control pills work because they alter many natural functions in the body.
Source: NIH
1. Daily Pill
The first thing to know when you learn how do birth control pills work is that you have to take a daily pill for 3 weeks, and then you have one week off before the next cycle. Our menstrual cycle is on average 28 days in length, so oral contraceptives work in the same way. Each pill is associated with a different strength of estrogen levels or a combination of estrogen and progesterone. These different strengths of hormone levels will be a replication of our natural levels. For 3 weeks you take one pill per day and then the fourth week you do not need to take a pill because this is your ‘period’ week, more information on that will be mentioned later. Taking the pill each day at the same time is vital for keeping effectiveness high.
Source: NIH
2. Prevents pregnancy
The next thing to know when learning how do birth control pills work is how they prevent pregnancy. Most women who take the pill are taking it for contraception purposes. The effectiveness of birth control pills comes in at about 91% for typical use (includes human error). With perfect use, the pill stands to be 99% effective when taken every day at the same time with no missed days. The pill prevents pregnancy through the administration of artificial hormones which will impact ovulation.
Source: NIH
3. Ovulation does not occur
The next thing to know when learning how do birth control pills work is that ovulation does not occur. Many may not know that on oral contraceptives, ovulation is shut off, and this is why you do not get pregnant. Ovulation is one of the most necessary parts of conception. In addition to this, birth control pills prevent pregnancy by thickening the mucus in the cervix so that the sperm have a harder time entering the uterus. Conception is dependent on the egg being in the fallopian at the same time that the sperms swim up into the fallopian tube. At that point, the sperm can fertilize the egg and conception occurs. When you do not ovulate the sperm can not fertilize. Birth control pills contain artificial forms of hormones that will turn off the production of hormones, thus the brain-ovary connection is severed.
The amount of hormones administered through the pill will simulate the hormone levels that a pregnant woman has. This works because when you are pregnant your body naturally does not ovulate. The body will prohibit ovulation so that a woman can not conceive while she is already pregnant. Due to this, the pill will give a false sense of pregnancy so the body will not allow ovulation to occur.
Source: NIH
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4. ‘Menstrual Cycle’
The next thing to know when learning how do birth control pills work is the ‘menstrual cycle’ that occurs while you are on it. The reason that it is put in quotes is because this menstrual cycle is not a true menstruation. Normal or true menstruation occurs because of a failure to fertilize an egg after ovulation. In the case of birth control pill use, the body will not release an egg and therefore no ovulation or true menstruation will occur. Well, you might be asking what is happening then on every fourth week of the birth control pill use? This bleeding is just a light shedding of the endometrium, but it is not correlated to an egg being shed or the normal build-up of the endometrial wall in preparation for pregnancy. This period that occurs on the pill is much lighter and less symptomatic because the bleeding is not associated with the natural hormonal output.
Source: NIH
5. Combination Pill vs Estrogen
The next thing to know about how do birth control pills work is the difference between estrogen and combination pills.
Women who take estrogen-only birth control pills usually struggle with heavy and painful periods and need some alleviation from that. Heavy bleeding can be caused by polyps which occur when there is enlarged tissue growth in the endometrial cavity. Estrogen functions to build up the endometrial wall for menstruation, so when estrogen levels are too high then heavy painful periods can occur. If only estrogen is administered through the pill, then natural estrogen production is inhibited and thus resulting in fewer period-related symptoms.
The combination pill includes estrogen and progesterone. The progesterone in the pill acts more to prevent pregnancy. Progesterone reduces the development of the follicle which holds the eggs in the ovary Through decreasing follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Without a surge of estrogen or LH, there will not be the development of the follicle and therefore no ovulation will occur.
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6. Issues can return post-use
The last thing to know about how do birth control pills work is that if you start taking the pills to alleviate a period-related issue (heavy flow, cramps, hormonal acne), these symptoms can return after you stop using birth control. This effect is called rebound and it occurs because birth control does not cure PMS or acne, all it does is put your body on hold temporarily. Additionally, after using birth control you may struggle with fertility as your body is trying to relearn how to produce optimal hormone levels. In this period, your periods may be inconsistent and ovulation may not occur for some time.
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