Menstruation during pregnancy

Menstruation during pregnancy. Bleeding and spotting during pregnancy

Menstruation and pregnancy. Two revolutionary changes in a woman's life, which will affect not only her physical, but often also her mental state. But can these two different, but related, cycles take place in the female organism at the same time? The answer is a resounding no, but the question that continues to plague many women in their second trimester is what causes first trimester bleeding?

Published: 12.05.2023
Updated: 04.12.2023

We will try to discuss this issue in the following paragraphs, including not only the most common causes of bleeding at the beginning of pregnancy, but also rare, but serious, diagnoses of women who suffer from heavy "menstruation" during pregnancy. So, we will clarify the situations when it is not necessary to panic, but also those that need necessary medical intervention, and therefore they need to be dealt with as quickly as possible.

It is definitely not menstruation during pregnancy

Normal menstruation as we know it is almost impossible at the beginning of pregnancy. It follows from biological theory that these two phenomena are completely mutually exclusive. Menstruation is only possible if the woman has not become pregnant. Every month, a process takes place in a woman's body, during which the lining of the uterus thickens so that the egg can nestle in these places. However, if successful fertilization does not occur, the tissue is flushed from the body.

If fertilization occurs and the egg does implant in the lining of the uterus, the hormones will ensure that the tissue stays in place and supports the developing fetus. It is very important to keep one thing in mind. While menstruation during pregnancy is impossible, the probability that a woman will become pregnant during her menstrual cycle is definitely not zero. A woman's cycle is variable in the later days, and therefore the probability of successful fertilization increases more and more with the increasing days of menstruation.

Menstruation in pregnancy

Possible causes of bleeding in early pregnancy

As we mentioned above, menstruation is impossible in the first trimester of pregnancy, but it is quite common for bleeding to occur in the early stages of pregnancy, for several reasons that differ in degree of severity.

Implant staining as the most common cause

Menstruation cannot occur during pregnancy, but implantation bleeding during the first trimester is more common than one would expect. Spotting is completely normal in the first stage of pregnancy and is characterized by a light pink or dark brown color, which can remind many women of menstrual blood in the first or last days of the cycle.

Such bleeding can occur the first 5 to 11 days after fertilization, when the process of implantation of the egg into the pregnant mucosa in the uterine cavity takes place, while the bleeding in most cases causes injury to the lining of the uterus by the implanting fertilized egg. Spotting at the beginning of pregnancy is mild and its duration is individual for each woman. While some may last only a few hours, others bleed for several days. Because of the spotting, there is no reason to worry, but sometimes the discharge at the beginning of pregnancy can indicate a much more serious problem, so it is better to familiarize yourself with the possible causes and, if necessary, get examined by a doctor.

Blood clot causing menstruation in pregnancy

Subchorionic hematoma, also known as bloody effusion or blood clot, in the majority of women does not indicate a serious part of pregnancy. It is the formation of a hematoma between the uterine wall and the egg sac, and is manifested by vaginal, bright red bleeding. Its most frequent occurrence is in the 10th to 20th week of pregnancy, while it can very easily shrink or disappear of its own accord, and thus without medical intervention. This diagnosis is a reality for almost 10% of all vaginal bleeding during pregnancy. Subchorionic hematoma can be diagnosed through an ultrasound examination.

Causes of bleeding in pregnancy

Menstruation in pregnancy due to cervical lesions

Both during the menstrual cycle and during pregnancy, the female genital system is very sensitive. However, during pregnancy, this sensitivity increases extremely, due to the excessive occurrence of blood in the cervix. Light bleeding in the first trimester is therefore a very common phenomenon for many women. It occurs especially in the case of a medical examination of the pelvis or during sexual intercourse. There is no need to panic in this case either.

Ectopic pregnancy

This cause is already of a more serious nature. An ectopic pregnancy occurs in the first trimester of pregnancy when a successfully fertilized egg settles outside the uterus, most often in the woman's fallopian tube. Bright red, heavy menstruation during pregnancy is thus caused by further growth of the embryo in a place where it does not belong, while it can cause life-threatening damage to the female genital organs. Other accompanying symptoms to watch for are dizziness, blood clots, abdominal pain and intense cramps.

Painful and heavy bleeding due to abortion

One of the most sensitive topics related to pregnancy is precisely their threatening, unwanted terminations, which are accompanied by heavy bleeding during pregnancy. Miscarriage is one of the biggest concerns associated with first trimester bleeding. It most often occurs in the first 12 weeks of pregnancy. It is characterized by heavy vaginal bleeding, which is accompanied by extreme pain in the lower abdomen, lower back and severe cramps. The moment a woman registers any of the listed symptoms, it is necessary to seek medical help.

In connection with this cause of bleeding during pregnancy, it is also appropriate to mention the so-called vanishing twin syndrome, when a pregnancy is reduced from a multiple to a singleton. Therefore, only one fetus survives, while the second one is either washed out of the woman's body during a slight bleeding in the first trimester of pregnancy, or is absorbed within a few weeks by the placenta or the second fetus remaining in development.

Painful and heavy bleeding due to abortion

A molar pregnancy can also be a cause

A very interesting and insufficiently discussed phenomenon is the so-called molar pregnancy. We talk about it when there is an uncontrollable growth of the trophoblast, which is a structural tissue involved in the formation of the placenta, while this germinal tissue gradually turns into a cystic formation. There are three types of moles causing complications and bleeding during pregnancy.

While partial mole is the impossibility of further development of the embryo as a result of the fertilization of the egg by two sperm, or possibly one split sperm, which causes the egg to contain only 69 chromosomes, complete mole occurs as a result of the fertilization of an empty egg by one or two sperm. which results in an egg acquiring only 46 chromosomes coming from a male source.

In the first case, the fetus disappears by the 10th week of pregnancy, while the complete mole is removed by a procedure that ends the pregnancy, the so-called by cleaning the uterine cavity. While after a partial mole a woman can try to get pregnant after half a year, a complete mole and its possible consequences must be monitored, while the recommended waiting period before the next pregnancy is one year.

However, there is also a rare, malignant form of mole, an intense one, in which the trophoblast unstoppably spreads to the lungs, ovaries or organs of the abdominal cavity of a pregnant woman. Such a phenomenon is also manifested by bleeding during pregnancy, but also by the rapid growth of the uterus. It requires surgical treatment and subsequent chemotherapy. The scary thing is that this intense mole can occur not only in the early stages of pregnancy, but also more than 10 years after pregnancy or after the onset of menopause.

Placental change causing bleeding during pregnancy

"Menstruation" in advanced pregnancy, and therefore especially in the second trimester, can also occur due to the change of the placenta. Due to the possible premature separation of the placenta, this condition must be consulted with a gynecologist in order to avoid possible risks. Abruption of the placenta seriously threatens the life of the woman and the child. Separation of the placenta should initially only occur after birth.

Change of the placenta during pregnancy

Premature birth as a justification for bleeding during pregnancy

Premature birth, at any advanced stage of pregnancy, is accompanied by heavy bleeding combined with special pressures in the pelvis and regular contractions, the frequency of which, along with the level of pain, increases when the position of the pregnant woman changes. Such a condition requires urgent medical attention. Premature labor is said to be triggered by various factors between the 24th and 37th week of pregnancy.

Other possible causes of spotting in pregnancy

Apart from the above-mentioned causes of bleeding during ongoing pregnancy, vaginal discharge in the form of blood also commonly occurs due to hormonal fluctuations in the female body. It is in this way that the female body can adapt to the upcoming change. However, behind bright red bleeding during pregnancy, it is also possible to look for the placenta getting stuck in the wrong place. This is a serious problem that also requires a necessary medical examination.

However, "menstruation" during pregnancy can also be caused by various infections affecting a woman's genitals, such as the cervix or the vagina as such. However, sexually transmitted diseases such as chlamydia, gonorrhea or herpes can also be the source of infectious diseases that cause bleeding during pregnancy.

Spotting during pregnancy

When is consultation with a gynecologist necessary?

So it is probably clear to everyone that pregnancy is a period when a woman should place particular emphasis on any changes in her health. Bleeding during pregnancy is one of the symptoms that no pregnant woman should definitely ignore. Although it is true that light, short-term bleeding without other accompanying symptoms, caused either by the implantation of a fertilized egg or by physical irritation due to changes in the passing cervix during sexual intercourse or during a medical examination, does not indicate anything serious, there are also cases when a woman should not to wave "menstruation" during pregnancy.

Heavy, prolonged bleeding accompanied by other painful symptoms, such as migraines, dizziness, convulsions, vomiting, back and lower back pain, should be immediately consulted with a doctor. However, it is best to see your gynecologist regardless of the frequency or strength of the bleeding. Every human body is different, and thus reacts differently to internal biological changes. Therefore, it is recommended to seek medical help in case of bloody vaginal discharge in any trimester of pregnancy. Even if it was only to make sure of the true cause through ultrasound, palpation examination, or blood sampling.


Many women have experience with spotting and bleeding during pregnancy. Despite the fact that expectant mothers talk about "normal" menstruation, this is not a common phenomenon. Several women confirmed that their periods lasted for several months, although they were already pregnant, most of them had mild bleeding, or they encountered lighter spotting.

The most frequent questions - FAQ

Are you also interested in other aspects related to the topic of bleeding during pregnancy? Can you think of other questions that were not answered in the text of the article or in the question and answer section ? Feel free to put them in the comments below the article. We will try to answer them as soon as possible.

No, from a biological point of view, these two conditions are mutually exclusive. Bleeding similar to that which women experience every month during the menstrual cycle can also occur during pregnancy, but its causes are different. It is also appropriate to draw attention to the fact that while menstruation cannot occur during pregnancy, the opposite sequence of events, i.e. fertilization during menstruation, is still in play. Although the probability is low, it still exists.

No, spotting, i.e. weak bleeding with a dark brown color, accompanies the first trimester of pregnancy in 25 to 40% of the female population.

This can be caused mainly by irregular or minimal menstruation, to which a woman has become so accustomed that she does not notice anything suspicious about her menstrual cycle caused by an ongoing pregnancy. In such exceptional cases, the woman may not notice the pregnancy due to the absence of other accompanying phenomena, such as weight gain, heartburn, swelling of the legs or sensitivity to the movements of the developing embryo. Although such undetected pregnancies are rare, they are not impossible.

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