No, you cannot be pregnant and still have a period.
"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. "There are many reasons for bleeding during pregnancy," Hakakha says, "but you are not having a period."
But as your OBGYN will most certainly tell you, bleeding in pregnancy is not at all unusual. Here's what you need to know.
The reason you cannot be pregnant but still have a period is that a period, by definition, is the blood loss that occurs at the end of a menstrual cycle as a result of your egg not being fertilized by a 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 are 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.
Even though you cannot be pregnant and still have a period, bleeding in pregnancy — especially early on — is not uncommon. According to Dr. Hakakha, women can bleed in pregnancy for a variety of reasons.
One time bleeding commonly occurs is soon after the egg has been fertilized. "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.
According to Dr. Hakakha, other reasons you might see bleeding in the first trimester are a subchorionic hemorrhage (a blood clot that forms behind the developing placenta), a cervical infection, or placenta previa (when the placenta implants and grows over the cervix).
Bleeding in the first trimester can also be a sign of an ectopic pregnancy (when the fetus starts to grow in your fallopian tubes instead of your womb) or a miscarriage. Most miscarriages occur during the first 12 weeks of pregnancy.
"Both an early miscarriage and an ectopic pregnancy can present with spotting or bleeding. This is why any bleeding, particularly prior to the first ultrasound (where an intrauterine pregnancy would be confirmed), should be reported to your practitioner," advises Dr. Hakakha.
You can also bleed in the second and third trimesters of pregnancy, again as the result of various complications. Since you are pregnant, bleeding at either of these stages is still not defined as a period.
"Bleeding during pregnancy can occur from placenta previa, 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 true labor," says Dr. Hakakha. A placental abruption also tends to present with stomach pain as well as bleeding.
In addition, bleeding in later stages of pregnancy can be caused by preterm labor. Sometimes, when a woman passes her mucus plug from the cervix just before labor, the mucus-y discharge may have blood in it as well. There's also the much less dire possibility of postcoital bleeding (bleeding after sexual intercourse).
"Spotting during pregnancy is usually no cause for alarm, particularly when it is in the absence of cramping or abdominal pain," says Dr. Hakakha. "However, it is always a good idea to let your practitioner know about the spotting and let her decide if you need to be evaluated, or if it can wait."