What a Miscarriage Looks Like

Your period can differ from cycle to cycle for all sorts of reasons, from stress or illness (like the flu) to a chronic medical condition, a change in diet, extreme weight loss or weight gain, or fluctuations in hormones. Any of these can result in a flow that's heavier or lighter than usual, that lasts longer or for a shorter amount of time, and so forth.

If you experience heavy bleeding around the time of your period soon after receiving a positive pregnancy test result, it's possible you've experienced a miscarriage. Most miscarriages are one-time events caused by a genetic abnormality in the embryo.

But what if you don't know if you're pregnant? Is there any way to tell if your heavy bleeding is actually a miscarriage rather than a regular period?

What Happens During a Miscarriage

If the pregnancy ends before five weeks gestational age (the length of pregnancy after the first day of the last menstrual period) it is called a chemical pregnancy. The tissue (the fetus, gestational sac, and placenta) from an early miscarriage may not be obvious to the naked eye. Many early miscarriages look like heavy menstrual periods.

In a miscarriage that happens beyond 6 weeks, more tissue will be expelled. The expelled tissue usually resemble large blood clots. Depending on the point at which the pregnancy stopped developing, the expelled tissue could range in size from as small as a pea to as big or bigger than an orange. The gestational sac may also be discernible.

Possible Causes of Heavy Menstrual Bleeding

If you've been using birth control and have a heavy flow, it's unlikely (but not impossible) that your bleeding is, in fact, a miscarriage. No contraceptive is 100% effective, after all.

At the same time, birth control pills can lead to hormone imbalances which can bring about noticeable changes in menstrual flow. Some women, in fact, can have a rare reaction to a new contraceptive, causing their bodies to expel a decidual cast—a piece of tissue that is the shape and size of the uterine cavity. Decidual casts also can occur in women with ectopic pregnancies.

Some medical conditions can also lead to changes in the menstrual flow. Fibroids and hypothyroidism are both known to cause heavy menstrual bleeding.

What to Do If You Think You're Having a Miscarriage

Call your doctor to find out if you might need to be seen or even treated. Even over the phone, they should be able to make an educated guess as to the cause of the bleeding. If you're worried and can't get in touch with your doctor, go to the emergency room or urgent care.

You may be asked for a sample of the tissue that was expelled in your menstrual blood. If you have a history of miscarriages, your doctor may be able to test for chromosome abnormalities that might explain what happened.