A true period is the result of shedding of the endometrium, or lining of the uterus, which occurs as a result of ovulation (midcycle release of the egg) and the cyclic changes in estrogen and progesterone. Since women do not ovulate when they are pregnant, any bleeding during your pregnancy should not be confused with a period.
Although bleeding in pregnancy is common, it is never normal, explains Melissa Esposito, M.D. If a woman is pregnant and bleeding, with or without pain, she should call her doctor for further instruction. But don't immediately worry: While bleeding in the first trimester of pregnancy may signify either a miscarriage (or a threatened miscarriage) or an ectopic pregnancy, it also may be due to implantation.
When a fertilized egg implants in the uterus, 10 to 14 days after conception, it could cause parts of the uterine lining to shed. The bleeding may look like the normal start of your period or spotting, but if you think you may be pregnant, you should take a pregnancy test to be sure.
If you are experiencing a miscarriage (or a threatened miscarriage), you will usually have bleeding associated with uterine cramping. There may also be a passage of large clots from the vagina. If this is happening you should definitely seek care at the doctor's office or the local ER if after hours, Dr. Esposito says.
Another cause of bleeding during pregnancy is an ectopic pregnancy (or tubal pregnancy). The amount of bleeding with an ectopic may vary in amount and is usually associated with unilateral pain (pain primarily located on the left or right side) plus or minus dizziness or lighheadedness, Dr. Esposito says. Ectopic pregnancy can be life threatening if it ruptures, so the more rapid the diagnosis the better for the patient. If you having any of the above symptoms such as bleeding and pain, especially localized pain, you should call your doctor or get to the ER immediately. Implantation bleeding is usually fairly light but develops as the embryo is implanting into the uterine lining.
Often times, the cause of bleeding during pregnancy may not be known, which can feel very alarming for the patients and be very anxiety provoking. If you do seek medical attention, you might be told to go home and be on bedrest and pelvic rest until the bleeding stops. If this happens, your pregnancy will be monitored closely with obstetric ultrasounds and possibly blood tests to check the HCG levels if that is clinically indicated.