3 weeks of gestation: see which exams to take

The 3 weeks of gestation represent the moment when the fertilization of the egg actually occurs. So, in fact, it is the first week of pregnancy.

Therefore, in general, there is not much evidence of pregnancy before that time, considering that it is 3 weeks since the woman’s last menstruation

Some signs may appear from the third week, and tests can confirm the pregnancy. In this text, we will talk about this gestational phase and the development of the fetus. Come on?


How many months is 3 weeks of gestation?

The calculation of months of gestation is made from the woman’s last menstruation. Thus, even though it is the week in which fertilization actually occurs, the third week is considered half of the first month of pregnancy , which lasts until 4 and a half weeks. It is when the fetus begins to develop inside the uterus.

This gestational calculation is based on the DUM (Day of Last Menstruation) because, in general, it is difficult to determine the precise date of fertilization. For this reason, the LMP is adopted internationally as the start of gestational counts.

It is very common that the woman still does not know that she is pregnant at that moment, since the symptoms have not appeared (or are very subtle).

Exams at 3 weeks gestation

The moment of fertilization is the mark where the production of hormones begins to accelerate. Thanks to this, it is possible to check if you are really pregnant after 3 weeks of gestation. The tests done at this stage are:

Beta HCG

The most common pregnancy test measures a woman’s hormone concentrations of beta HCG. The hormone is produced by the placental-forming cells and is a fraction of the specific pregnancy hormone, HCG.

So, if there is a high hormonal level, there is an indication of pregnancy. Therefore, tests are done to measure hormone levels in the urine ( pharmacy test ) and in the blood (laboratory test).

At first, a blood test is more likely to identify HCG concentration in the first few days of pregnancy. However, there are pharmacy tests that can be done on the 1st day of menstruation delay.

Even so, with 3 weeks of gestation, the hormonal changes are still not as intense. In the coming weeks, they will be more pronounced and it will be easier to have the confirmation of the pregnancy.


The ultrasound examination can only identify the baby (the gestational sac, initially) after the fifth or sixth week of pregnancy. Therefore, ultrasound is not necessary in the first month of pregnancy .

How is fetal development?

Fertilization happens at 3 weeks of gestation. The zygote (the first cell of the fetus) begins to multiply and form the embryo, which will give rise to the baby’s first organs.

At this point, the embryo is approximately 0.15mm in size. In the coming days, the embryo will be directed to the uterus and fixed on the uterine wall, where it will receive the necessary nutrients to begin its development.


When the egg is fixed on the uterine wall, it is common for an intense vaginal discharge to occur, accompanied by bleeding.

This bleeding, called nidation , is natural and is often confused with menstruation. However, it can also be one of the first indications for women to suspect their pregnancy.

The third week of gestation is just the beginning of the embryo’s development, which will soon begin to grow exponentially.

At the end of the first month, with the confirmation that she is pregnant, the woman needs to start medical monitoring of the pregnancy (prenatal) and take the necessary care so that everything goes well during the pregnancy.

This is the moment that marks the beginning of a long process. It is important to control anxiety , take a deep breath and wait for the next phases to arrive.