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4 Reasons Why You May Have a Missed Period on Birth Control

4 Reasons Why You May Have a Missed Period on Birth Control

  • Sonia Easaw, M.S., MPH
    By: Sonia Easaw, M.S., MPH
    Reviewed By: Shannon DeVita DNP, FNP-BC, CPNP-PC, Julie Lamonoff, CNM, OBGYN-NP
    Updated:

Is something wrong if you don't get your period while taking birth control pills? Maybe, but more likely there's a reasonable cause for it.

We know that it'll take some convincing, though, because, let's face it - you're taking birth control to prevent pregnancy, and this is an important question.

Give it to me straight: Why did I miss my period on birth control?

Before you get too worried about whether to get a pregnancy test, remember: Birth control pills are 91% effective with average use and over 99% effective if you take them correctly, every day.

Menstrual bleeding changes are normal when you're on birth control, say global women's health experts.

You could have lighter, more frequent, or no periods at all when you're taking the pill or using another hormonal method.

Unless you have other pregnancy symptoms or health conditions, doctors say that it is common for women on hormonal contraception to have missed periods. You could also have early or late periods, or just spotting. Therefore missing your period while on birth control isn't necessarily cause for alarm unless you have other concerning symptoms. Always talk to your doctor about it, though, if you're worried.

Editor's note: Don't get us wrong, though. Regular periods are a sign your body is working as expected. But we're specifically talking about periods on birth control, which don't necessarily fall into that bucket. Find out why further down.

Key stats on the failure rate of birth control pills:

  1. For women who use the oral contraceptive pill perfectly (correctly and consistently), the percentage of women experiencing an unintended pregnancy in the first year of use was 0.3%.

  2. With typical or average use (maybe they missed some pills here and there), the percentage of women experiencing an unintended pregnancy in the first year of using the pill was 9%.

Is your period on birth control a "real" period?

Missing your monthly period isn't a good sign, right?

It's more complicated than that when you're taking birth control. But once you know this, you'll never forget it:

Getting your period on birth control is not biologically necessary.

Why you usually get a period on the "off-week"

If you get your period on birth control pills, let's say during the 7 days of placebo "sugar" pills, it's because the makers of the original combined oral contraceptives succumbed to societal and cultural pressures to mimic the naturally occurring menstrual cycle - not because it was biologically needed.

So a missed period on birth control doesn't necessarily mean something's wrong. Okay, here's some quick science to back this all up because this is some deep, revelatory stuff. So here goes...

Periods 101: Our bodies, ourselves

Okay, so women have a menstrual cycle, aka as a monthly period. What exactly is your period, we mean, naturally speaking? Like what does your period look like if you were not taking birth control?

Getting ready for baby-making, science style

Your period before the pill was like this: Your body thinks you might want to get pregnant and so it gives you a chance every month (from the time you get your first period until your last period, let's say in your 50s). Every menstrual cycle, your body is preparing for you to be pregnant, and your uterus is building up the lining in anticipation for the new baby.

Menstrual bleeding: Discard that uterine lining!

But news flash to your uterus: you're not planning on having any babies this month. Typically, the levels of your hormones (estrogen and progesterone), your body's chemical messengers, go up and down depending on the situation. Suppose you don't get pregnant this cycle. In that case, your estrogen and progesterone levels fall and tell your body to start menstruating, which means discarding the monthly buildup of the lining of the uterus.

Guess what? Your period on birth control is a "withdrawal" bleed

When you have your menstrual period while taking birth control, it's called a "withdrawal" period because you're not taking the active pills with the hormones in them. Essentially, it's a hormone withdrawal, and the bleeding happens because of this lack of hormones.

Remember when we said it's all about ovulation? (Well, actually, we didn't say that just kidding.) Here's the thing: ovulation is when your ovaries release an egg to be fertilized by a sperm to make a baby. Fertilizing an egg is what we're trying NOT to do when you take birth control. Birth control primarily prevents ovulation.

Okay, so that was a lot. But now you know. And all of the rest will make sense. Get ready for all of the reasons why you could have a missed period on birth control.

The 4 reasons why you can have a missed period on birth control

Okay, so you're going about your business of taking your birth control pills every day and whatnot.

Here's why you may have a missed period during the scheduled time, for example, during an off-week (when you take your inactive pills for 7 days if that's what your pill pack says):

Number 1: Because you're taking birth control.

Okay, so that sounds weird. But really, one reason why you may have a missed period on birth control is because of the birth control pills themselves. Don't just take our word for it, though. The clever people at the National Institutes for Health, the World Health Organization, etc., all say the same thing. Specifically, the NIH says that secondary amenorrhea (the medical-speak for missing three periods in a row) can result from certain birth control pills, injectable contraceptives, and hormonal intrauterine devices (IUDs).

Global health experts try and counsel women worldwide on this very fact, especially in places where women want to avoid getting pregnant but do not use modern contraceptive methods.

Here are 3 things you should know about your periods while you're on hormonal birth control:

  1. Changes to menstruation are normal when you're using a contraceptive method.

  2. Once you stop your birth control, your periods should resume to your normal pattern. Your chances of getting pregnant will return to normal.

  3. If you're using a hormonal contraception method, the absence of your period by itself (without other signs) does not automatically mean you're pregnant.

Number 2: Because of physical or emotional stress

So there's this thing called the hypothalamus, which is a gland in your brain. If something's wrong, your hypothalamus can't kick off the menstrual cycle, and you won't ovulate.

Characteristics that can affect your hypothalamus and lead to missing your period include:

  • Emotional and mental stress

  • Weight loss and low body weight

  • Deficient intake of food/eating disorders

  • Too much exercise

Researchers often see this happening in adolescent girls, where the common triggers are stress, weight loss, and excessive exercise. Girls at this time of their lives can undergo common life events that bring a lot of emotional and mental toll, like changing schools or becoming sexually active. Disordered eating during adolescence is also common.

Number 3: Because of an abnormal balance of hormones like PCOS

You may have heard of a condition called Polycystic Ovary Syndrome (PCOS). This is when the body makes more androgen hormones (sex hormones) than it needs, which can cause fluid-filled sacs called cysts to form in the ovaries. These sacs of fluid interfere with ovulation - pretty much they keep the egg from releasing. Women or girls who have PCOS either do not get their period for months on end or have irregular periods.

PCOS is a common reproductive health disorder that affects adolescent girls, and pediatricians often consider it first if they have irregular periods.

Another cause for an abnormal balance of hormones is a thyroid disorder. Your thyroid is a small gland in the shape of a butterfly that sits at the base of the neck. The thyroid produces hormones that can affect menstruation, and if it's overactive or underactive, that can cause you to miss periods. As you can see, it's all about those hormone levels.

Number 4: Because of pregnancy (or breastfeeding/entering menopause)

Okay, this is the reason we've all been waiting to hear. Note that doctors say that it's common for women on birth control to have irregular or no periods, and further evaluation usually isn't needed unless there are concerning symptoms. That said, every contraceptive has a failure rate. If you've missed birth control pills during the month and had unprotected sex, you should consider this possibility.

Here are a few common symptoms the Mayo Clinic says women experience in early pregnancy:

  • Missed period

  • Breast tenderness

  • Nausea and vomiting

  • Fatigue

  • Having to urinate more often

Other less obvious signs of pregnancy include:

  • Moodiness

  • Bloating

  • Light spotting

  • Cramping

  • Constipation

If you're wondering more about when to take a pregnancy test, click here for more info.

Note that if you're breastfeeding, that could also be a reason you're missing your periods on birth control. Entering menopause will also do that to you!

Recap: The 4 reasons why you may have missed your period on birth control

We talked about 4 solid reasons why you may have missed your period this month, even though you're taking birth control. Here they are again:

  1. The birth control pills themselves may cause you to miss periods

  2. Emotional/physical stress on your body

  3. Gynecological problems like PCOS

  4. Natural causes like pregnancy.

The main message is generally not to worry about being pregnant if you've been taking your pills and have no other concerning symptoms. But if you're concerned, you can always ask your health care provider.

What about periods on other types of birth control?

Okay, so you should also know that different contraceptive methods can lead to various bleeding changes. For example, this means that you may completely stop getting your period on some methods like the IUD.

Let's quickly go into the various methods and how they can change your monthly menstruation patterns:

  • An IUD like Mirena™ can reduce menstrual blood loss by 90%, though it's a gradual process over 3-6 months. Your periods may stop altogether after a few months, which is expected and not a reason to worry or seek treatment.

  • An arm implant (Nexplanon™) may come with some unscheduled breakthrough bleeding or spotting. When the makers were doing their clinical trials to get approval for the device, on average, during any 90 days, 22% of women did not get their periods.

  • A birth control shot (Depo-Provera) commonly causes women to stop their periods. Within the first 3 months, some 10-30% of women do not get their periods anymore, and 50% stop getting periods after year 1.

  • A progestin-only pill (mini-pill) is something you'd take if you can't tolerate estrogen. With the mini-pill, you'd expect every type of bleeding irregularity, including not getting your period. About 50% of women on the mini-pill still get a monthly period. Still, the bleeding patterns are more unpredictable than taking a combined hormone (progesterone and estrogen) birth control pills. About 10% of women on the mini-pill still stop getting their period.

  • A vaginal ring like Nuvaring™ or Annovera™ allows for the withdrawal bleed, but unscheduled bleeding or spotting is expected in the first few months.

  • A transdermal patch (Xulane™) also allows for the withdrawal bleeding week. Women usually have spotting or unscheduled light bleeding in the first few months of using the patch.

As you can see, different methods of hormonal birth control can cause different menstruation patterns, but it's all pretty commonplace for birth control methods to "have their way" with withdrawal bleeding.

Summary

To sum it up, women who take birth control commonly experience changes to their periods or won't get their period at all after some time. Four reasons why you may miss your period, or it comes late or early, are: because of the mechanism of the hormonal birth control itself, emotional or physical stress, gynecological problems, or pregnancy. But if you're worried about possible pregnancy or another health condition, you should talk to your doctor.

Sources:

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