If you've ever gotten a surprise period [1] or had multiple days of unexpected spotting [2], you're experiencing something called breakthrough bleeding. Many things can cause breakthrough bleeding, including hormonal birth control, the morning-after pill, a sexually transmitted infection (STI), or hormonal abnormalities, and as you might have guessed, figuring out exactly what's causing the breakthrough bleeding is key to treating it. (Because most of us aren't begging for extra periods over here.)

But first: what actually is breakthrough bleeding? Essentially, breakthrough bleeding is vaginal bleeding that occurs midcycle, or any time outside of your period, says Jennifer Roelands, MD, board-certified ob-gyn and founder of Precision Health MD [3]. If you're pregnant, breakthrough bleeding would be any vaginal bleeding that occurs during your pregnancy. And while breakthrough bleeding can be normal and expected in some situations (looking at you, hormonal birth control), it may also be a sign of something more serious, especially for people who are postmenopausal. Either way, it's probably not something you want to be dealing with on the regular, so PS spoke with Dr. Roelands to find out what breakthrough bleeding is, why it happens, and what you can do to get it treated.

Experts Featured in This Article

Jennifer Roelands [4], MD, is a board-certified ob-gyn and founder of Precision Health MD [5].

Breakthrough Bleeding: Why Does It Happen?

"There are many causes of breakthrough bleeding," Dr. Roelands says, "but they can be broken down into two categories: hormone causes and structural causes." The most common causes, she says, are stress and missing days of a birth-control pill.

Hormone-related causes of breakthrough bleeding include:

• Hormonal birth control, such as an oral contraceptive pill, hormonal IUD, implant, shot, vaginal ring, or skin patch. Breakthrough bleeding is especially common within the first few months of starting a new hormonal birth-control method.
• Inconsistent dosing of birth-control pills (aka forgetting to take the pill).
• Taking emergency contraception [6] (aka the morning-after pill).
• Menopause or perimenopause (the time when your body is transitioning to menopause).
• Polycystic ovarian syndrome [7] (PCOS).
• Endometriosis [8].
• Vaginal infections, such as a yeast infection [9] or trichomoniasis. These are considered hormonal causes rather than structural causes because infections are a disruption in the bacteria or yeast ratio caused by a lack or imbalance of hormones. "For example, menopausal women have more vaginal infections because low estrogen causes the bacteria content in the vagina to be off," Dr. Roelands says.
• Miscarriage.

Structural causes of breakthrough bleeding may include:

• Uterine fibroids [10].
• Polyps.
• STIs, such as chlamydia [11].
• Vaginal lesions.
• Prolapse.
• Fragile cervix.
• Ovarian cysts [12].
• Cervical cancer, womb cancer, or vaginal or vulval cancer.

Breakthrough bleeding may also be caused by rough sexual intercourse [13] or lifestyle changes, such as stress or weight loss.

Related:

Yes, an IUD Can Fall Out — Here's What to Do If It Happens [14]

Breakthrough Bleeding on Birth Control: Is It Normal?

Breakthrough bleeding is common among people on hormonal birth control, according to the American College of Obstetricians and Gynecologists [15] (ACOG). It's especially common if you smoke or if you're using low-dose or ultra-low-dose methods, which include some versions of the pill, the implant, and IUDs. The low dose of hormones can become insufficient to prevent the withdrawal response [16], triggering some spotting or bleeding before you reach the placebo week of pills.

Breakthrough bleeding is also likely if you take your birth-control pills inconsistently. Missing a pill, Dr. Roelands explains, causes the levels of hormones in your blood to drop. "The pill gives you a set amount of estrogen and progesterone each day," she says. "If you miss the pill or take it late, the body sees this drop in hormones for the day as a signal it is time to have a withdrawal bleed," aka you're at the end of your active hormones and about to start a placebo week.

If you take the pill continuously (without a monthly "placebo week" that triggers a period), you may also be likely to experience breakthrough bleeding. "The longer you go without allowing the body to shed the lining it makes, the more chance you will eventually break through and have a period," Dr. Roelands says. This usually doesn't happen until you've gone four to six months without a period, she adds. "The lining builds up the entire time and does not shed, which makes it more difficult for hormones (pill) to control it from shedding."

The good news is that your birth control is still effective at preventing pregnancy, even if you experience breakthrough bleeding. If you're using pills or the ring, continue using them normally, even if you're having breakthrough bleeding.

Breakthrough Bleeding: Treatments and When to See a Doctor

Most breakthrough bleeding is light, Dr. Roelands says, and often resolves with time, especially if it's related to your body adjusting to hormonal birth control or situational stress. That said, you should talk to a doctor about your breakthrough bleeding if:

• You have pain with the bleeding.
• You're experiencing heavy bleeding.
• You're bleeding for more than five days.
• You're postmenopausal. "Breakthrough bleeding can be more serious if you are postmenopausal as it can indicate a malignancy," Dr. Roelands says. "All bleeding if you are postmenopausal needs to be evaluated."
• You're pregnant.
• You think you have an STI [17].
• You're consistently bleeding outside of your normal pattern.
• You're at all concerned about any bleeding pattern.

Related:

Implantation Bleeding Can Look a Lot Like Your Period — How to Spot the Difference [18]

Treatment for breakthrough bleeding depends on the cause. If your doctor determines that the cause is structural, such as a fibroid, ovarian cyst, or polyp, you may require surgery to remove the structure, though many ovarian cysts "do not require surgery and will spontaneously resolve," Dr. Roelands says.

If your bleeding is related to hormones, your doctor may want you to get blood work done to determine the specific cause and may put you on medications if necessary. If it's related to your birth control, you may discuss trying a new method, such as a contraceptive with a slightly higher dose of hormones or a monthly contraceptive, instead of a continuous-use one.

To sum it up, breakthrough bleeding will often go away on its own, but if it's bothering or concerning you, it's best to check in with your doctor to determine what's causing the issue. Treatment options are available and can help you avoid the inconvenience and stress that can come with breakthrough bleeding.