Ask an Expert: Can I have my period and still be pregnant?

Answer from Firmine Jean-Baptiste, M.D., obstetrics and gynecology, Providence Women's Clinic, Providence St. Vincent Medical Center: Not really. During the first three months of pregnancy, you may experience light vaginal bleeding, but it's not a true period.

Let's refresh our understanding of menstruation. Every month, your uterus prepares a lush lining of cells to provide a home for an embryo. After ovulation, if your egg meets up with sperm, the fertilized egg bores into this cushiony lining.

If the egg is not fertilized, however, the body knows it has no use for that month's lining. The cells break down and are shed, in the form of your menstrual period.

You can't have that sort of period and be pregnant.

Spotting early in pregnancy can be confusing, however, especially if your menstrual flow is ordinarily light, and the bleeding coincides with the usual timing of your period. Here are some causes of normal spotting during the first trimester:

  • As the embryo is getting situated in the uterine lining, and the placenta begins to develop, the site where the embryo is attaching can bleed a little.

  • The blood supply to the cervix increases immediately when you become pregnant. The surface of the cervix is thin, and the pressure from the extra blood can make a few of the tiny blood vessels pop, causing slight bleeding.

  • The changes in the cervix can make it more sensitive to irritation from intercourse, and that can lead to a bit of bleeding.

Women who are pregnant generally feel an extreme tiredness that does not accompany menstruation. (Most pregnant women also develop breast tenderness, but that may not feel different from breast tenderness that accompanies your period.)

Pregnancy spotting is much lighter than what most women experience during their period, and it would last for fewer days than the typical period.

If you have abnormally light bleeding when you'd expect your period, and pregnancy is possible, go ahead and take a pregnancy test. Today's home pregnancy tests are very sensitive and accurate.

One caution: Bleeding in early pregnancy is a danger sign in the relatively rare case of ectopic pregnancy.

Ectopic pregnancies occur in about 20 of 1,000 pregnancies in the United States, according to the latest data from the Centers for Disease Control and Prevention. In an ectopic pregnancy, the fertilized egg starts developing outside of the uterus, usually in a fallopian tube. In that case, some of the uterine lining may slough off, which might look like a dark period. You would experience other symptoms, such as lower abdominal pain and cramping on one side of the pelvis.

Again, if you have any question, I encourage you to take a pregnancy test. The earlier you begin prenatal care, the better. I'd also like to remind anyone trying to conceive to begin taking prenatal vitamins now. That way, your body and the baby have what they need from the very start of your pregnancy.

Updated March 2011

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