How Birth Control Affects Your Body

have been taking my birth control pill for the past five years, and I’d be lying if I said I had literally any idea what it was doing to my body.

I mean, I know the effect it has on my body. I know I’m not pregnant. So it must be doing something right. But what’s been going on inside of my body every single day for the past five years to make that happen? I had no idea — until I had the chance to talk to Dr. Nancy Beth Lebowitz, a gynecologist, an assistant attending physician at Weill Cornell Medicine, and clinical instructor at Cornell Medical School, about what we should know about birth control and what it’s doing to our bodies.

Now, Dr. Leibowitz wants to make it clear that birth control can be different depending on the type you’re taking. What’s going on in your body with your pills on a weekly basis could be different from what’s going on in mine, but there are a few general things that are happening for all of us, no matter what pill we’re taking.

Read along and get ready to learn, people!

How our cycles work without birth control

For those of you who, like myself, weren’t paying much attention freshman year of high school in biology class, let me give you a quick refresher courtesy of Dr. Lebowitz.

There are two key players when it comes to our menstrual cycles: the luteinizing hormone (LH) and the follicle stimulating hormone (FSH).

“Normally, what happens is that the follicles where the eggs develop are stimulated by the FSH,” Dr. Lebowitz explains. “One follicle gets ahead of the other, it’s kind of like a race. That’s the lead follicle.” The lead follicle is the one that releases the egg.

In the middle of your cycle, your LH levels go up in what’s called the “LH surge.” The rise in LH causes you to release your egg — aka ovulation.

You’re at your most fertile when you’re ovulating since that’s when the egg is released for potential fertilization, which is why people who are trying to get pregnant often use “ovulation-predictor kits” to try to figure out when is a good time to try.

Your testosterone levels also go up while you’re ovulating. Why? Dr. Lebowitz explains, “Testosterone rises with ovulation to increase your desire to mate.” In other words, it’s making you horny.

“Once the lead follicle releases the egg — it turns into something called the corpus luteum,” Dr. Lebowitz explains. “Instead of secreting estrogen as the follicle did, the corpus luteum secretes progesterone to prepare the uterus for possible pregnancy in the event the egg gets fertilized.”

Progesterone is a key player in the whole making-a-baby process as it gets the lining in your uterus ready for pregnancy. If you don’t wind up pregnant, the corpus luteum involutes.

Once your corpus luteum involutes, your progesterone levels fall. At this point, your lining sheds (bleeds) because you didn’t get pregnant. And that, my friends, is what we know as the “period.”

Alright, so now you get what’s going on in your body when you’re not on the pill. What’s going on when you are?

What does birth control do to change your cycle?

Birth control is different when you get down to the specifics, but in general, every pill does two things: It prevents ovulation and thins your uterine lining.

If you were paying attention to the first part, this is a pretty grand master plan when it comes to the whole not-getting-you-pregnant thing since ovulation is when an egg is released for fertilization and a thick uterine lining is necessary for a healthy pregnancy.

But what chemicals are going into your body in order to achieve that goal? Well, most pills are primarily made up of two different hormones: a synthetic estrogen and progestin (a synthetic progesterone).

The estrogen is there to suppress the FSH that’s releasing your egg.

The progestin is there to suppress the LH and thin the uterine lining, which then helps prevent implantation.

In fact, because of progestin’s effects, Dr. Lebowitz encourages women who are trying to get pregnant to wait a couple months after going off the pill to give their lining time to rebuild itself.

“If you get pregnant too soon off the birth control pill,” she warns, “you might be at higher risk of a miscarriage because the lining is too thin.”

An important thing to note here is that, in preventing ovulation, birth control is also suppressing that testosterone spike we said usually makes you horny. That’s why some women report a decrease in libido as a result of the pill.

So what makes various pills different?

Almost all birth control medicines with estrogen have the same kind of estrogen in them. The difference is generally the amount of estrogen in each pill. Some have more, some less. It all depends on what you, as a patient, need.

The type of progestin, on the other hand, can vary since different pharmaceutical companies use different kinds. For example, Dr. Lebowitz explains, “some progestin can cause more acne, so if you have somebody with bad skin, you’re going to give them a different pill with a different kind of progestin.”

Other common side effects of birth control, such as moodiness or weight gain, can also be a result of the type or amount of progestin in your pill. Though weight gain can also be a side effect of estrogen, Dr. Lebowitz explains that the kind of progestin that’s right for you totally varies from person to person. “One pill may make one woman moody,” she explains. “Another pill might be fine for another person.”

Progestin-only pills are also a popular option for women with health problems such as blood clots or estrogen-dependent tumors. Dr. Lebowitz elaborates, “some people can’t take estrogen because of the risk of blood clots or if they have fibroids, which are less likely to grow with progestin-only pills.”

Is there anything you should be worried about while on the pill?

Again, the different side effects that come along with your birth control vary based on what kind of birth control you’re taking, but there’s one more general warning Dr. Lebowitz wants women to be aware of.

“Progestins, [like the ones found in your birth control pills] do mildly increase the risk of breast cancer if you’ve been on them for a very long time.” What constitutes a very long time? Dr. Lebowitz says anywhere over eight years.

So, if breast cancer runs in your family, Dr. Lebowitz strongly encourages you to talk to your doctor about how long you’ve been on the pill.

That being said, those same progestins in your pills that are increasing your risk of breast cancer are also decreasing your risk of uterine and ovarian cancer. Dr. Lebowitz advises, “you’ve got to take that all into account.”

Having trouble deciding which pill is right for you? Freaking out about whether or not you’ve been on your pill for too long? No matter what your concern is, never hesitate to reach out to your gyno and have a real conversation about what’s the best fit for you.