Implantation bleeding or menstruation? What is it and when can it occur?

Approximately one in four women detect a slight loss of blood caused by the nesting of the fertilized egg in the wall of the uterus. This is what is known as implantation bleeding .

The loss can last one to three days, is usually lighter than menstrual bleeding, and is darker. It occurs in the first weeks of gestation, at which time the uterus is highly irrigated and bleeds easily.

As the embryo adheres to the wall of the uterus, small veins and arteries that normally supply the endometrium rupture, causing bleeding.

This occurs between six and ten days after fertilization , a period that agrees with the expected date for menstruation, which is why it is often confused with its arrival.

Sometimes it is just a drop of blood and in others it can be mistaken for a light menstruation. Implantation bleeding does not follow a fixed rule, it can occur in a single pregnancy or in all.

From fertilized egg to implanted embryo

When the sperm enters the ovum, fertilization and the formation of the zygote (first fertilized cell) takes place. Within 72 hours the zygote becomes a morula (zygote cleavage) and four to five days after fertilization, the morula becomes a blastocyst (or blastula).

The blastocyst is made up of two groups of cells, one external and one internal. The internal group will become the embryo, and the exterior, the membrane that will protect and nourish it during pregnancy. From when the blastocyst is implanted in the endometrium is when it begins to speak of an embryo .

When the blastocyst reaches the uterus, normally six or seven days after fertilization, it begins to produce extensions that allow it to adhere to the uterine lining and “bury itself” in the endometrium. This is known as embryo implantation (see image).

Implantation is a fundamental phase of pregnancy, as it allows the embryo in its primary stage to receive nutrients and oxygen from the mother through her blood.

Fourteen days after fertilization, the embryo is firmly nested in its new home. This is where a new being will grow and develop.

Can be confused with menstruation

As we have mentioned, by the time it occurs, implantation bleeding can be confused with the arrival of menstruation when it is actually a sign of the beginning of pregnancy .

This can cause anxiety since it is not known if the bleeding is a sign of pregnancy or that the period has come. To avoid confusion it is important to observe the staining. It is not usually like a normal rule, it is usually dark red or brown, mild, and lasts a few days (usually one or two and never more than five).

These days you should pay special attention to your body, since observing other signs can help you define whether or not it is a pregnancy. Watch for other possible early pregnancy symptoms like breast tenderness, nausea, increased basal temperature, malaise, and tiredness.

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Confirmation of pregnancy

To clear up any doubts, the most effective and fastest thing is to take a pregnancy test, however it may be early for it. For the result to be reliable, it is important to know when to get tested .

It must be done at least one day late to ensure that the pregnancy hormone (human chorionic gonadotropin) is detected, although certain tests claim to detect it from the first week after conception.

If you suspect that you may be pregnant and notice heavy bleeding, severe abdominal pain and cramps, you should see a doctor, as it could be related to a problem.

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