Why Can IUDs & Implants Stop Your Period?

The varieties of birth control available to women are rather astounding — an implanted tiny stick of plastic in my arm that will prevent me from getting pregnant for three years? Are you sure this isn't magic? — but some of them come with a slightly alarming side effect: certain forms of contraception, like hormonal IUDs and implants, result in your period stopping altogether. It's confined to specific hormonal contraceptives, and it can either be a massive relief or a rather confusing experience. And it also raises a lot of questions: what causes it? Is it safe? Is my body just building up a backlog of periods to unleash upon me, The Shining-style?

After my insertion of a contraceptive arm implant several months ago, I haven't had the whisper of a period, a side effect that was unexpected but not unwelcome. I do recognize, however, that the absence of a period isn't a boon for everybody; what to me represents the end of ruining underwear and running out of tampons at pivotal moments (I am a disorganized woman) is, to others, a vital part of their monthly program of reassurance that they're not carrying anybody's kid, and that's not something you should feel ashamed to want. The good news is that period absence on the hormonal IUD, the contraceptive implant, or the mini-pill is a normal side effect, and is actually part of the accepted treatment plan for menorrhagia, or excessive bleeding; it's not a sign that your uterus is suddenly malfunctioning, or that you're losing your feminine hormones, or that you'll never have a period again.

Here's the science behind why certain types of contraception can make periods vanish like a magic trick, and why that isn't something you should panic about.

Why Can Your Period Vanish?

The lessening or complete vanishing of periods on various forms of birth control is down to one particular kind of synthetic hormone: progestin. The progestins, as they're called (there's not just one version, and many birth controls use different varieties), are synthetic versions of a hormone your body naturally produces called progesterone. It's one of the hormones that determines your body's ovulation and menstrual cycles; it's a "regulatory" chemical, and its levels in the body act as signals for everything from the uterus lining to cervical mucus.

Hormonal IUDs, implants, and the mini-pill are all based exclusively on the release of progestins into the female body (the combination pill also uses estrogen, and the copper coil just uses the phenomenal powers of copper to derail the whole pregnancy process, including decapitating sperm) — and progestins are the responsible party for the vanishing or drastic lessening of your menstrual bleeding, because of what they do to your uterine lining.

Progestins target the lining of the uterus in particular, making it seriously thin as a preventative measure against any eggs implanting in it. As you'll know from health class, the lining of the uterus is what's shed during a period, and its serious thinness may simply indicate to the body that it doesn't require to be shed at all. Progestin levels are also a signaling system, and their monthly drop in the blood is what tells the body to start peeling off the insides of the uterus; if progestin levels are kept high, that signal sometimes just doesn't send.

The progestin used in many hormonal IUDs, a variety called levonorgestrel, are particularly known for causing menstrual irregularities and vanishing; it's telling that levonorgestrel is also used in emergency contraception, and a 2006 study found that after taking a levonorgestrel morning-after pill, periods were temporarily but significantly altered.

According to the National Library of Medicine, studies have shown that progestin-only birth control methods often tend to reduce bleeding, making them a common prescription for people who suffer from extensive, heavy menstrual bleeding. Hormonal IUDs are a particular favorite for treatment; a landmark study across Europe in 2013 found that they're likely the best option for treating the condition.

Is It Anything To Be Worried About?

If you're worried that not having a period is causing some kind of blockage of period blood and lining that will eventually need to be removed or flushed out, don't. The thinning of the endometrial layer (the uterus lining) on progestins means that there's no real danger; the body isn't producing a huge, thick lining that will cause trouble unless it's shed. It's becoming teeny-tiny, and the body basically sees no point in expending energy and blood on the effort of expelling it.

It can be a gradual process, too; the IUD brand Mirena has done a study on the particular evolution of bleeding patterns among women with heavy periods who've just been fitted with its hormonal IUD, and found that they started to see a reduction in bleeding after about three months, with an average of 90 percent reduction after six months. What happens in the initial period can differ significantly between women, but up to 70 percent of all Mirena IUD users will stop having a period within two years of getting one, whatever their previous period experiences.

What If You Want To Keep Your Period?

An absence of periods is not for everybody. While many women embrace the lack of trouble and potential stains, it can also freak others out; without that monthly reminder of "not pregnant," you can feel a lack of reassurance, even if your IUD, implant, or contraceptive is meant to be taking care of that for you.

The women's health website Bedsider recommends that women contemplating getting an IUD do a serious compare and contrast between hormonal and copper options; the copper ones often make periods longer and a bit worse in the first few months before returning to normal, and aren't hormonal at all. The monthly "withdrawal bleed" on the combined pill is also meant to be a reassuring element; it was built into the original design of the pill to allay religious objections to altering the "natural" functioning of the female body and give women the experience of a monthly bleed. (Periods on The Pill are not "periods" in the true sense of the word; they represent a small shedding of the uterine lining in response to a lowering in hormone levels, but aren't actually fulfilling the normal function of a "clean out" to prepare the uterus for a potential pregnancy the next month.)

If you do want the reassurance of a period and don't have health issues that make an IUD or implant the preferable option, then it's perfectly legitimate to go to your doctor and ask to explore your options. It's your body; you've got a right not to panic every month.

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