Bleeding During Pregnancy: Could It Be a Period?

Many women experience some bleeding or spotting during different stages of pregnancy. In fact, about 30% of pregnant women may experience some bleeding during the first trimester (the first three months of pregnancy), while very few experience this during the next 6 months. Could it be a menstrual period? Could it be a dangerous sign of pregnancy?

You Cannot Have a Period When You are Pregnant

You cannot possibly have a period when you are pregnant. Your monthly period is caused by your menstrual cycle. Normally, during this cycle your brain releases hormones that signal your reproductive organs to perform specific actions. An increase in your sex hormones (estrogen) causes ovulation, when your ovary releases an egg that subsequently travels through the fallopian tubes. Meanwhile, another hormone called progesterone causes the thickening of the lining of the uterus, forming a protective layer of blood and tissue in preparation for pregnancy, should it occur.

If your egg is not fertilized, your progesterone levels will suddenly drop. This causes the bloody shedding of the uterine lining that was built up in the past few days. This is what is commonly known as your menstruation or your menstrual period.

However, if the egg is fertilized by a sperm, pregnancy ensues. During this stage, your body adapts to a condition that is focused on providing nutrition for your baby. This time your brain sends hormonal signals to your ovaries to stop your regular menstrual cycle. Instead, the body will now be providing the proper environment for the baby to grow. As a result, your progesterone levels will continue to increase for the next nine months of pregnancy to support the development of the uterine lining that helps prepare for the growth and development of your baby.

This explains why you cannot have a menstrual period while you are pregnant. If you continue to have regular menstrual periods while you were pregnant, it would involve shedding of the uterine lining that supports your baby's growth, which is biologically impossible. Spotting or bleeding during pregnancy is therefore caused by something other than your normal monthly period.

Overview of Bleeding During Pregnancy

First of all, it is important to know that vaginal bleeding during any stage of pregnancy may be risky, so you should call a doctor if you have any kind of bleeding when pregnant.

Vaginal bleeding that occurs in the first three months of your pregnancy is known as first trimester bleeding. This is a common problem in the early stage of pregnancy, and causes complications in 20 to 30 percent of pregnancies. Bleeding may vary from light spotting to heavy bleeding with clots.

Vaginal bleeding in the next 6 months is likewise considered abnormal, although the causes may vary from those of the first trimester.

Vaginal bleeding in the last few weeks of pregnancy must be regarded as a real emergency even it is very mild or unaccompanied by other symptoms like abdominal pain. Bleeding during this period may range from mild to very rapid, with or without abdominal pain. Brisk bleeding or hemorrhage complicates about 4 percent of pregnancies and is the most common cause of demise in pregnant mothers.

Causes of Bleeding During Pregnancy

Let us look into the possible causes of bleeding during the different stages of pregnancy.

Causes of Bleeding in the First Trimester

Twenty to thirty percent of all first trimester pregnancies are affected by vaginal bleeding. About half of these cases end up in miscarriage, which means the loss of the baby. Vaginal bleeding in the first three months of pregnancy may be caused by several different factors:

Implantation bleeding: This is a normal part of pregnancy which occurs during the implantation of the embryo into the uterine wall. If you experience minimal bleeding or spotting that coincides with your scheduled menstrual period, it may be caused by pregnancy. This is not a cause for concern.

Postcoital bleeding: Vaginal bleeding after sexual intercourse is a normal occurrence during pregnancy and may not be a cause for worry.

Threatened miscarriage: If you are having some bleeding accompanied by cramping, you may be in danger of miscarriage or abortion. Based on an ultrasound, the fetus is found inside the uterus but the outcome of your pregnancy is undetermined. This condition may occur if you have a urinary tract infection, dehydrated, using certain drugs or have experienced physical trauma. If the fetus is abnormal a miscarriage may also occur, but it may also happen for no apparent reason.

Spontaneous abortion: The most common cause of first trimester bleeding is a spontaneous abortion, or a lost pregnancy. If your bleeding and cramping seem to have slowed down and your ultrasound shows an empty uterus, you may have a completed miscarriage. Causes are the same as in threatened abortion.

Incomplete miscarriage: If you are bleeding, cramping, passing blood clots or tissues and your pelvic exam shows your cervix is open, a miscarriage may be in progress. When the cervix closes the miscarriage is not completed and this occurs if the uterus begins to contract before all the fetal tissue has passed, or if there is an ongoing infection.

Blighted ovum: A blighted ovum is the failure of an embryo to develop, as shown by an ultrasound image of an intrauterine pregnancy, without an embryo. This may occur in cases of fetal abnormalities.

Fetal death: If the developing baby dies inside the uterus, bleeding may occur. This can occur at any time during pregnancy and may be caused by same reasons as a threatened miscarriage during the early stages of pregnancy. Although it is very uncommon during the second and third trimesters of pregnancy, bleeding occurs due to the separation of the placenta from the uterine wall or because of insufficient blood flow to the placenta.

Ectopic pregnancy: An ectopic pregnancy (or tubal pregnancy) is the most dangerous cause of first trimester bleeding and occurs in about 3 percent of all pregnancies. It occurs when the fertilized egg implants outside of the uterus, commonly in the fallopian tube. As the embryo grows, it can rupture the fallopian tube and lead to life-threatening bleeding. Symptoms include pain, bleeding and lightheadedness. Most cases occur before the tenth week of pregnancy.

Half of the women who experience ectopic pregnancy have risk factors for ectopic pregnancy including a history of previous ectopic pregnancy, pelvic inflammatory disease, fallopian tube surgery or tubal ligation, infertility, having an IUD (a birth control device) in the uterus, smoking, or frequent vaginal douching.

Molar pregnancy: You may have a molar pregnancy when your ultrasound shows the presence of abnormal tissue inside the uterus instead of a developing fetus. This is a type of tumor that develops as a result of the hormones of pregnancy, but is usually not life-threatening. However, in rare cases the tumor is cancerous and it may invade the uterine wall, ultimately spreading throughout the body. The cause is generally unknown.

Vaginal bleeding may also be caused by reasons unrelated to pregnancy. For example, trauma or tears to the vaginal wall may bleed, and some infections may cause bleeding.

Causes of Bleeding in Late Pregnancy

Most commonly, bleeding after the first trimester is due to a placental problem. The placenta is the structure which connects the baby to the wall of your womb, so that nourishment can be provided to it. Other causes of bleeding may be due to abnormalities in the vagina or cervix.

Placenta previa: Your placenta may lie over the cervix. The abnormal position of the placenta causes bleeding and it is called placenta previa. This is the cause of about 20 percent of bleeding in the last trimester and occurs in 1 out of 200 pregnancies. Risk factors include having multiple pregnancies, previous history of placenta previa and prior delivery by Cesarean section.

Abruptio Placenta: This condition occurs in 1 in 200 of all pregnancies, when a normal placenta separates from the wall of the uterus prematurely. The exact cause is not known, but risk factors include increased blood pressure, trauma, cocaine or tobacco use and prior history of placental abruption.

Less common causes of late-pregnancy bleeding include uterine rupture, injuries, polyps, cancer, and varicose veins.

What to Do When Bleeding During Pregnancy

Vaginal bleeding may not be a normal symptom at any time during pregnancy. Do not try home remedy for bleeding during pregnancy. You must report it immediately to your health care professional, including information about the amount of blood you have lost and a description of your symptoms.

However, you must immediately go to a hospital's Emergency Department if the following conditions occur:

  • You have severe bleeding , cramps and contractions
  • Your vaginal bleeding lasts for more than one day and you are not able to see a doctor
  • You feel very dizzy or about to pass out
  • You develop a fever over 38.05 C or 100.5 F
  • You experience abdominal pain that is worse than your normal period, or you have severe pain in your abdomen, pelvis, or back
  • You have undergone an abortion and later develop a fever, pelvic pain, or more bleeding
  • You develop increased abdominal or pelvic pain within the first week after treatment for ectopic pregnancy.