Bleeding During Pregnancy: What You Need To Know

Although bleeding during pregnancy is common, it's sometimes a sign of something more serious. Let's consider some of them.
Bleeding During Pregnancy: What You Need To Know

Last update: 16 December, 2022

Bleeding during pregnancy is relatively common. Of course, this doesn’t mean it’s always harmless. Although this is generally the case, sometimes bleeding is a symptom of a life-threatening condition for the fetus or the mother. Today we’ll show you the most frequent causes according to each stage of pregnancy.

In early pregnancy, some women experience slight bleeding when the fertilized egg attaches to the wall of the uterus. This is known as implantation bleeding, and it occurs an average of two weeks after conception. Apart from this, some mild and severe conditions can also be behind bleeding during pregnancy.

Causes of bleeding during pregnancy

Since any changes during pregnancy can put the life of the fetus and the mother at risk, you should always be aware of any signs that could be warning you of a possible problem. Bleeding is one of the most frequent, a sign that must be distinguished from spotting.

Spotting occurs to a lesser extent. It’s usually just a few drops of blood, and it can appear from conception to the end of pregnancy. On the contrary, bleeding is more abundant – so much so that it can soak your underwear and other clothes. Let’s see what its causes are according to each trimester of pregnancy.

Bleeding in the first trimester of pregnancy

According to The American College of Obstetricians and Gynecologists (ACOG), up to 25% of pregnant women develop bleeding during the first trimester of pregnancy. Therefore, it’s the most common stage when pregnant women can experience this phenomenon.

It’s most likely due to the formation of blood vessels in the uterine area. Because of this, first-trimester sex, pelvic examinations, and routine tests can cause light to moderate bleeding. In less frequent cases the bleeding can point to the following:

Ectopic pregnancy

Bleeding during pregnancy may be due to an ectopic pregnancy
Sooner or later, ectopic pregnancies can be life-threatening. For this reason, seeing a doctor promptly is essential.

An ectopic pregnancy occurs when the fertilized egg doesn’t implant itself in the wall of the uterus, but elsewhere. It usually occurs in the fallopian tubes, but it can also occur in the ovaries, the abdominal cavity, or the cervix.

The ovum cannot develop outside the uterus, so the ectopic tissue must be removed to avoid complications in the mother. Otherwise, the growth can tear the surrounding tissue and cause massive bleeding. Blood tests and ultrasounds are used for its diagnosis.

Spontaneous miscarriage

A miscarriage is considered to be any loss of the fetus that occurs in the first trimester of gestation. It’s relatively common, and it can even happen before a woman knows she is pregnant. According to researchers, the frequency of having one increases with previous pregnancies, so that up to 43% of women with more than one pregnancy can experience it.

In addition to bleeding in pregnancy, other symptoms are abdominal pain and fluid or tissue that’s expelled through the vagina. Contrary to popular belief, exercise and sexual intercourse don’t cause miscarriages. Its causes include abnormal development of the fertilized egg, infections, and uncontrolled diabetes.

Molar pregnancy

A molar pregnancy occurs when the fertilized egg develops as abnormal tissue and not as fetal tissue. It is classified into two types: complete and partial. In the first case, there’s no presence of fetal tissue, while in the second there is. Both cases can lead to miscarriages.

Keep in mind that molar pregnancy is a rare condition. In general, the ratio is 1 case in 1000 pregnancies and it’s associated with genetic abnormalities. Pregnant women over 35 and under 20 are more likely to have a molar pregnancy. Since it’s associated with complications, it should be treated as soon as its first symptoms are seen.

Bleeding in the second trimester of pregnancy

Pregnancy problems decrease a little in the second trimester of pregnancy, at least if we compare it with the previous case. Despite this, bleeding during this trimester can alert you to mild, moderate, or severe complications. Let’s look at some examples.

Infections in the uterus or vagina

Such as bacterial vaginosis, vaginal yeast infections, or sexually transmitted infections (chlamydia, gonorrhea, and so on). Alterations in the immune system that occur during pregnancy make the body more prone to infection. When they occur in the uterus or vagina, they can cause bleeding.

Incompetent cervix

Also known as cervical insufficiency, it occurs when cervical tissue weakens and leads to premature labor or miscarriage. The cervix is the part of the lower uterus that makes its way into the vagina. Under normal conditions, the fibers and the muscles that compose it gradually relax before labor to allow the passage of the fetus.

However, when you have cervical insufficiency, the muscles and fibers can begin to relax prematurely. It often happens in the second trimester of pregnancy and can lead to two possibilities: miscarriages and premature births. It can be difficult to diagnose as symptoms are mild and sometimes non-existent.

Previous placenta

Bleeding during pregnancy may be due to a placenta previa.
Placenta previa is a real emergency that must be resolved as soon as possible, as the risk of severe bleeding is high.

This condition develops when the placenta totally or partially covers the cervix. Under normal conditions, the placenta attaches to the sides or top of the uterus. When it does it in the lower part (cervix) it generates moderate or intense bleeding of bright red color.

It usually develops in the second trimester of pregnancy, although it can also extend into labor. When not diagnosed early, it can lead to premature labor or heavy bleeding during birth. The risk of developing placenta previa increases after age 35 and with previous pregnancies.

Bleeding during late pregnancy

Lastly, light or moderate bleeding in late pregnancy can be a sign that labor has started. Usually, the bleeding is accompanied by cervical mucus, the plug that lines the cervix. This combination of blood and mucus that precedes the contractions are sometimes referred to as a bloody show.

Although we have only brought you a few explanations, you’ll have seen that bleeding during pregnancy has many different causes. Since it’s impossible to determine the exact cause without consulting a specialist, the best thing to do is to seek medical attention as soon as you manifest it.

In this way, you can rule out any conditions that could endanger your life or that of the fetus and proceed with treatment if this is the case. Don’t delay, as taking action in time can help to remove any cause that could get in the way of a healthy pregnancy.

  • Cohain, J. S., Buxbaum, R. E., & Mankuta, D. Spontaneous first trimester miscarriage rates per woman among parous women with 1 or more pregnancies of 24 weeks or more. BMC pregnancy and childbirth. 2017; 17(1), 1-7.

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