Experts share why it's physically impossible to have a period while pregnant, and they give alternative reasons for bleeding during the first, second, and third trimesters.

By Jennifer Barton
Updated April 12, 2021
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Can you get your period while pregnant? The short answer is no. "Women can certainly have vaginal bleeding during a pregnancy, but when they bleed, they are not having a 'period,'" explains Michele Hakakha, M.D., a board-certified obstetrician and gynecologist based in Los Angeles and co-author of Expecting 411: Clear Answers and Smart Advice for Your Pregnancy. Keep reading to learn why menstruation stops during pregnancy, as well as other possible causes of spotting during the first, second, or third trimester.

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Credit: Ema Woo/Shutterstock

Why You Can't Have a Period While Pregnant

A true period is blood loss that occurs at the end of a menstrual cycle as a result of your egg not being fertilized by sperm. When an egg goes unfertilized, hormones—the ones that control the release of the egg into your fallopian tubes and cause your womb lining to thicken—drop in levels at the end of the month. Your womb lining then disintegrates and is shed in what we commonly refer to as a period.

If you're pregnant, an egg has already been fertilized and is growing as an embryo within the walls of your uterus. Since your womb lining is not being discarded at the end of each month, you no longer have a period. This is why one of the early signs of pregnancy is a missed period.

Other Reasons for Bleeding in Pregnancy

Although you can't have your period and be pregnant, bleeding while expecting—especially in the first trimester—is not uncommon. According to Dr. Hakakha, women can bleed in pregnancy for a variety of reasons. Here are a few common ones.

Implantation Bleeding

"Many women experience something called 'implantation bleeding,'" says Dr. Hakakha. "This can occur at the time the fertilized egg, known as the embryo, reaches the uterus and nestles itself into the lining of the uterus." Implantation bleeding tends to present as light pinkish or brownish spotting, and it occurs 10 to 14 days after conception. The bleeding may look like the normal start of your period.

Sexual Intercourse

There's also the possibility of postcoital bleeding (bleeding after sexual intercourse), says Melissa Esposito, M.D, a board-certified reproductive endocrinologist at Shady Grove Fertility Center in the Washington, D.C., area. You might also bleed after a pelvic exam because your cervix is more sensitive while pregnant.

Miscarriage

Most pregnancy losses occur during the first 12 weeks of pregnancy. A miscarriage (or a threatened miscarriage) usually presents as bleeding associated with uterine cramping. There may also be a passage of large clots from the vagina. If you have these symptoms, alert your doctor right away.

Ectopic Pregnancy

Bleeding in the first trimester can also be a sign of an ectopic pregnancy (when the fetus starts to grow outside of your womb, usually in a fallopian tube). The amount of bleeding with an ectopic pregnancy may vary. It's also associated with unilateral pain, dizziness, or lightheadedness, says Dr. Esposito. Ectopic pregnancy can be life-threatening if untreated, so rapid diagnosis is key.

Pregnancy Complications

According to Dr. Hakakha, other reasons you might see bleeding during the first trimester are a subchorionic hemorrhage (a blood clot that forms behind the developing placenta), a cervical infection, placenta previa (when the placenta implants and grows over the cervix), or benign cervical polyps.

During the second and third trimesters of pregnancy, bleeding can also result from vasa previa (where the blood vessels of the placenta are in an abnormal location and cross over the cervix), a placental abruption (where the placenta begins to pull away from the wall of the uterus prematurely,) or labor, says Dr. Hakakha. 

The Bottom Line

Although bleeding in pregnancy is common, it's never normal, explains Dr. Esposito. If someone is pregnant and bleeding, with or without pain, they should call their doctor for further instruction.