You're On The Pill, So What Actually Happens During Your Cycle?

By Mia Abrahams

Here at THINX, we’re all about embracing your cycle, which means, first and foremost, knowing what the hell goes on in your body every month, and the huge role your hormones play in your mood and overall wellbeing.  But, for someone like me, who takes the pill, I sometimes feel a little left out of the conversation. When everyone is talking about embracing their flow, I wanna be like “same, namaste”, but tbh I usually skip my periods, and I don’t really know what my hormones are up to anyway.

I know I’m not the only one who feels this way (thank you for all your comments and notes!), and according to the CDC, 62% of women (aged 15-44) are currently using contraception. Among women using contraception, 25.9% of women use the pill, and about 11% use intrauterine devices (eg. IUD). Among younger women (15-24), nearly 1 in 4 are on the pill. That’s a damn lot of us.

So in the interest of menstru-education, let’s take a look at what happens during your cycle when you’re on the pill. (IUD peeps, don’t worry, I got you next week!)

Last week on, This Is Your Period:

Just to recap, an average cycle (without any birth control) has four main players: estrogen, progesterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH). These hormones control your cycle by thickening your uterine lining (so you can grow that hypothetical baby), letting your body know when to ovulate, and, if there’s no pregnancy, giving your body the go-ahead to shed that lining (aka. period time!)

The way I like to think about the hormone cycle is like that 90s game Mouse Trap— the ball sets off one thing, which hits another, which slingshots into another, and rolls down a slide, — a chain reaction until you catch the mouse (or a baby, I guess). You need all the different parts to happen to get the end result.

You can see this chain reaction process in the diagram below:

The pill is made of synthetic hormones, most commonly a mix of estrogen and progestin (which is the name for synthetic progesterone). The “minipill” is just progestin. There are a whole bunch of different pills, both in terms of brands and hormone levels, so to keep things simple, we will be talking about the most generic (a combo of estrogen and progestin). If you want to know what’s in your pill, it should tell you on the packet.

So how does the pill stop you from getting pregnant?

In short, taking the pill stops you from ovulating. No ovulation, no egg ready to be fertilized by sperm. How? Well, remember our Mouse Trap analogy from earlier? The pill basically puts a stop to that chain reaction we already talked about by synthetically giving you a level amount of progestin and estrogen. Without the dip and rise of estrogen and progesterone, FSH and LH aren’t activated, and your body isn’t given the signals it needs to ovulate, or thicken your uterine lining in preparation for a baby.

* Note, this diagram doesn’t show the little spikes in your hormones you get depending on how many hours ago the pill was taken (it peaks after about two hours).

Also, the estrogen in your pill will help prevent breakthrough bleeding mid-cycle.The progestin in your pill prevents your uterine lining from thickening, but also stops your cervical mucus from thinning like usual, so that a sperm reaching the cervix will have a hard time getting through! Clever, huh?

So, what’s with the bleeding?

In an average cycle for someone not taking birth control, once your body works out there’s no pregnancy, your progesterone and estrogen levels drop, causing the uterine lining to disintegrate and flow out your V—a period! The drop in estrogen & progesterone also causes PMS (which is why the pill can minimize PMS symptoms—less drop in hormones, less #feelings and sore boobs).

So we aren’t ovulating, and we aren’t getting our uterus ready to have a baby… why do I still get my period when I take sugar pills?

The withdrawal from the hormones when you take the sugar pills, particularly the estrogen, triggers the breakdown of your uterine lining. While it might look and feel the same, it’s not a “real” period— it’s more like a “withdrawal bleed.” Because the uterine lining hasn’t been thickened to prepare for a potential pregnancy like it usually would, it is usually shorter or lighter than a regular period. There literally is less to shed.

Because the pill prevents the uterine lining from thickening, there is no buildup of blood or lining, and you don’t need to get your period for any biological reason. And, as many women’s health experts suggest, it’s perfectly fine to skip your period (good news for me!).

Go forth and menstruate (or not)!

Of course, some women/real menstruating humans prefer to have their period once a month (it’s a good reassurance you aren’t pregnant— remember, the pill is not 100% effective). Some real menstruating humans prefer their period once, twice, or three times a year (sometimes it isn’t possible to go that long, if you get breakthrough bleeding). Ultimately, it’s your body and your choice — do what feels best for you! If you have concerns about your pill, always remember to ask your handy-dandy health care professional. It’s worth it to get it right.