Period bleeding while pregnant is common and rarely serious when it presents during the first 12 weeks of pregnancy. While the type and amount of vaginal bleeding may lead some women to believe they are experiencing a menstrual cycle, it is impossible to menstruate during pregnancy. This is because pregnancy prevents ovulation, thereby ending the building and shedding of the uterine lining that takes place during menstruation.
Causes of Period Bleeding While Pregnant
There are many possible causes of bleeding during pregnancy, some of which are extremely serious. All bleeding requires medical evaluation, but your treatment and prognosis depend on the cause of your bleeding and your overall health.
Early Pregnancy Bleeding
Bleeding may occur during the first trimester of pregnancy for a variety of reasons, not all of which indicate a serious problem. Nearly one in five women will experience bleeding to some degree during the first months of pregnancy. However, because early pregnancy bleeding is a symptom of miscarriage and ectopic pregnancies, you should always report any vaginal bleeding to your doctor immediately.
Miscarriage - Most miscarriages occur during the first trimester and most are not preventable. In addition to bleeding, signs of an impending miscarriage include lower abdominal pain and passing tissue and clots through the vagina. The cramps may range in severity from strong menstrual cramps to severe pain.
Ectopic Pregnancy - Ectopic pregnancies are a medical emergency. An ectopic pregnancy occurs when implantation takes place outside the uterus, usually in a fallopian tube. Symptoms are similar to those of a miscarriage in the beginning and may include vaginal bleeding, lower abdominal cramping, and low levels of hCG. Many women also experience a sharp, one-sided pain in the abdominal area. Previous ectopic pregnancies and a history of tubal infections and pelvic surgery increase the risk of an ectopic pregnancy.
Molar Pregnancies - A molar pregnancy is diagnosed when an embryo fails to develop or when abnormal tissue begins to grow inside the uterus. Molar pregnancies are also called gestational trophoblastic disease. Your doctor may suspect a molar pregnancy when routine blood tests show abnormally high hCG levels. Other symptoms include vaginal bleeding, a lack of fetal heart tone, and grape-shaped clusters of tissue that are visible on ultrasound.
Other Causes - In addition to the above causes of early period bleeding while pregnant, implantation, infection, and cervical trauma may all trigger bleeding during pregnancy. Implantation bleeding is often mistaken for a light period, as it typically occurs near the time menstruation is expected. The bleeding may last for several days, disappear within hours, or be absent altogether.
Late Pregnancy Bleeding
Bleeding during the second and third trimesters of pregnancy often indicates a potentially serious condition that requires prompt treatment to preserve the health of the mother or fetus. You must consider any bleeding during the last two trimesters a medical emergency.
Placental Abruption - Vaginal bleeding late in pregnancy may be a sign of placental abruption, a condition where the placenta detaches from the uterine wall before labor ends. This condition is rare, affecting only one percent of women, and it nearly always occurs during the last two to three months of pregnancy. Symptoms of placental abruption include vaginal bleeding, which may be severe, and stomach pain. At greatest risk for early placental detachment are women over the age of 35 years, those who use cocaine, women with high blood pressure or sickle cell anemia, and women with a history of previous abruptions or stomach trauma.
Placenta Previa - When the placenta is located low enough in the uterus to block the cervix, placenta previa is diagnosed. This condition is a medical emergency. Bleeding may occur with or without pain. Women who have already given birth, especially by cesarean section, women carrying multiple fetuses, and those with a history of uterine surgery are at increased risk for placenta previa.
Preterm Labor - When vaginal bleeding occurs before the 37th week of pregnancy, it may indicate the beginning of preterm labor. Depending on how early in the pregnancy you are, your fetus may be at risk for complications caused by early delivery and low-birth weight. Signs of preterm labor are the same as those that signal normal labor, such as pelvic or abdominal pressure, backache, uterine tightening or contractions, a blood-tinged vaginal discharge, and stomach cramps.
Other Causes - Not all bleeding during the second and third trimesters is serious. Many women experience temporary, light bleeding following sex. Cervical inflammation, infections, or cervical growths may also cause bleeding. Never assume the cause of your bleeding is not serious. Any bleeding late in pregnancy requires immediate medical evaluation.
When to Seek Medical Help
Call your doctor as soon as possible for advice if you experience vaginal bleeding during the first three months of pregnancy, especially if your bleeding is accompanied by pain or fever. Any time you experience bleeding during the second or third trimesters, you must call your obstetrician immediately or go to the nearest emergency room, especially if you experience:
- Severe bleeding or contractions
- Vaginal bleeding that continues for more than 24 hours
- Vaginal bleeding combined with a fever higher than 100.5 degrees F
- Increased pain following treatment with methotrexate for an ectopic pregnancy
- Severe localized or one-sided pain in your back, pelvis, or abdomen
- Bleeding, pain, or fever following an abortion or miscarriage
- Fainting or severe dizziness
Testing and Diagnosis
If you experience period bleeding during pregnancy, your doctor will perform a complete physical and gynecological exam. You will also receive an ultrasound of your uterus and abdomen and instructions for blood and urine tests. Depending on the suspected cause of your bleeding, you doctor may order a complete blood count, a blood type and Rh, a serum quantitative bhCG, and a urinalysis.
Unless the cause of your bleeding is obvious during your office examination, it may take several days before you receive a diagnosis. Try to remain patient and relaxed during this time, as stress will only complicate your condition. Distract yourself with movies or books, get plenty of rest, and lean on family members for support. In most cases of pregnancy bleeding, both mother and baby suffer no long-term effects.