What Causes Breakthrough Bleeding — & When To See A OB/GYN

I have an extensive calendar tracking my period's coming and going. I know exactly when it'll show up, when it'll leave, and how long it'll last — but sometimes, even with the most regular period in the world, I can get thrown for a loop and experience some spotting, or even a day or two of a heavier, period-like flow, at a seemingly random time. This phenomenon is called breakthrough bleeding.

It's nothing to freak out about. Breakthrough bleeding is fairly common, and it has several possible causes, many of which are innocuous. We asked Mary Jane Minkin, MD, OB/GYN at Yale University School of Medicine, about the various culprits of breakthrough bleeding, whether there's anything you can do to avoid it, and when you should see a doctor.

Simply put: Breakthrough bleeding refers to vaginal bleeding that occurs when it's not "supposed" to, typically when you're in between periods, Dr. Minkin says. Breakthrough bleeding is also sometimes called spotting. It typically resembles the blood you'd see at the beginning or end of a period: light red or brown. (When you get pregnant, you can experience something similar called implantation bleeding, which is light bleeding that occurs within seven to fourteen days after fertilisation.)

In general, it's nothing to be concerned about, Dr. Minkin says. But if it starts happening regularly, like every month, it can be a sign that something's up and you should see your doctor. (A good reason to track your menstrual cycles.)

Birth control is one of the most common causes of breakthrough bleeding. If you forget to take one or two pills in a month, the cessation of hormones can trigger spotting, Dr. Minkin says. If you "skip" periods using the pill (by not taking the week of placebo pills and going straight to the next week of hormone pills), you may experience a little breakthrough bleeding, especially during the first few months, according to the Mayo Clinic.

It's totally safe to skip periods in this way, and the breakthrough bleeding is often just your body adjusting, not a sign of anything scary. If someone has been doing it for months in a row and starts experiencing breakthrough bleeding, Dr. Minkin says she'll tell patients to take the placebo week of pills and have a period before returning to the hormone-containing pills. But talk to your OB/GYN about the best fix for you.

Breakthrough bleeding can also occur in people who are on a low-dose hormonal birth control pill, Dr. Minkin says. Your body may acclimate to that low dose and experience a mild withdrawal response while you’re taking the hormones, causing breakthrough bleeding. Even if your pill has worked for you for years, you may suddenly notice that you're spotting for a few days in between periods. That's a sign that it may be time to switch to another type of birth control, she says. Talk to your OB/GYN about making a change.

Finally, if you have a new IUD, breakthrough bleeding is pretty common in the first three months of having it. It should stop on its own over time; if it persists, talk to your doc.

Breakthrough bleeding during pregnancy isn't uncommon, especially in the first trimester. But it's always a good idea to immediately let your OB/GYN know if this happens to you, Dr. Minkin says. It could be nothing, but it's better to play it safe. If you experience bleeding that's heavier than some light spotting, that's also a sign you should call up your doctor. It could potentially mean something serious, such as an ectopic pregnancy or miscarriage.

If it's not birth control or a pregnancy causing your breakthrough bleeding, it could be stress. When stress levels rise, your body responds by secreting alpha-amylase, an enzyme that can trip up ovulation. This can cause late periods, unexpected periods, longer periods, lighter periods, and even nonexistent periods.

Conditions including polycystic ovary syndrome (PCOS), uterine fibroids, and certain infections can also cause bleeding that occurs at times other than when you're on your period, Dr. Minkin says. If you experience spotting or bleeding and symptoms including irregular periods, bleeding during or after sex, discharge, pelvic pain, a different-than-normal smell, or anything that seems new or concerning to you, see your OB/GYN as soon as possible to get to the bottom of the issue.

Very often, breakthrough bleeding is normal. If you start spotting month after month, if the bleeding is heavy or lasts longer than a couple days, or if the spotting is accompanied by other symptoms, then Dr. Minkin advises you talk to a medical professional. But if you're not pregnant and it happens once or twice, it goes away quickly, and it never happens again — there's probably nothing to worry about. See your doctor if you want to (you know your body best). Or grab a panty liner and wait it out.