First Trimester Bleeding

You’ve shared the exciting news of your pregnancy with your friends and family. Then, one morning you wake up and notice a spot of blood on your underwear, and suddenly you're as frightened as you've ever been.

Don't panic. Although bleeding during pregnancy is never considered "normal," bleeding during the first trimester is very common. In fact, approximately one-quarter of all women who deliver healthy babies experience some bleeding in the first trimester.

Of course, bleeding can also be a sign of impending miscarriage, so it's important to discuss any bleeding with your midwife or doctor. She or he will probably wish to examine you (though not necessarily on an emergency basis), and will most likely order an ultrasound test to further evaluate your pregnancy.

What causes bleeding in the first trimester? And what type of bleeding is likely to indicate a miscarriage? One possible cause of light bleeding in the first trimester is related to the aggressive growth of the placenta. As the placenta establishes contact with the maternal circulation, some bleeding of the uterine wall may occur. This could cause retro-placental bleeding (a small collection of blood behind the placenta) and some of the blood may escape, causing vaginal bleeding.

There are several signs that may indicate the bleeding is a symptom of impending miscarriage. The most sensitive sign, and the one that your practitioner will probably ask you about first, is pain. In an impending miscarriage, bleeding is almost always associated with some lower abdominal cramping. Also, the volume of bleeding is generally quite a bit heavier in an impending miscarriage than in a normal pregnancy.

A blighted ovum is the most common cause of miscarriage. This term is somewhat misleading because it is not necessarily the ovum that is abnormal, but rather the combination of the ovum and sperm. The resulting chromosomal defect is so severe that although the pregnancy advances, development cannot proceed beyond the earliest stage. In most cases of blighted ovum, only the placental tissue, not the embryo, has developed. A blighted ovum does not indicate that either parent has a chromosomal abnormality. It affects only the fertilized ovum in question. There is no reason to believe that it will happen again in a future pregnancy.

This has important implications for dealing with miscarriage, both medically and psychologically. Because a blighted ovum is determined at the moment of conception, nothing can be done to prevent a miscarriage. If it's going to happen, it's going to happen. This also means that if you do have a miscarriage, you should never blame yourself. Virtually nothing you do can disrupt a normal pregnancy and, conversely, there is nothing you can do to save an abnormal one.

Lastly, bleeding may also be a sign of a much less common condition-ectopic pregnancy. Ectopic pregnancy, also known as tubal pregnancy, occurs when the fertilized ovum fails to travel all the way down the fallopian tube to the uterus. Instead, it implants in the wall of the fallopian tube. Such a pregnancy can never be successful. It may also cause serious health complications for the mother. An ultrasound test is often very helpful in diagnosing ectopic pregnancy.

back to Pregnancy FAQs