Ultrasound during pregnancy. Fetal ultrasound norms by week

July 5, 2025July 5, 2025

A woman is usually referred for her first ultrasound during pregnancy at 12-13 weeks of pregnancy.
This early examination method is extremely important. The doctor will be able to assess the primary formation of the fetus by fetal ultrasound, and evaluate the process of organ and system formation.

First ultrasound during pregnancy

In some cases, the first ultrasound during pregnancy can be performed earlier. Firstly, to confirm the presence of pregnancy, and also to exclude the fact of ectopic pregnancy. Suspicion of ectopic pregnancy requires mandatory examination using ultrasound – only in this way will it be possible to reliably establish whether this pathological condition really occurs. And only in this way will it be possible to intervene in the situation in time and carry out the necessary cleaning, otherwise serious consequences cannot be avoided.

The reason for an earlier ultrasound can also be alarming symptoms in the form of vaginal bleeding (or bloody discharge) and nagging pain in the lower abdomen. Such symptoms with a high degree of probability signal a threat of termination of pregnancy. And, although it is very difficult to determine whether there is a threat of miscarriage using only an ultrasound method, however, through such a study it is possible to find out the cause of the bleeding. Based on the ultrasound results, the doctor will be able to comprehensively assess the situation and give the woman appropriate recommendations.

At what stage will an ultrasound show pregnancy?

Very often a woman goes for an ultrasound, still only suspecting pregnancy, without a referral from a gynecologist and of her own free will. Such actions are usually dictated by the desire to find out whether it is worth talking about pregnancy, when characteristic symptoms are present, and the test does not show the result.

The question arises: at what stage will the ultrasound show pregnancy and does it make sense to go for an examination at 1-2 weeks of delay in order to finally decide? The answer is – it does: an ultrasound can show pregnancy already at 3-4 weeks, and this is exactly the same 1-2 weeks of delay in menstruation.
But not always, if the ultrasound shows a fertilized egg at the earliest stages, we can guarantee the presence of pregnancy. Unfortunately, the fertilized egg may be empty and not contain an embryo, and it will be possible to establish this only from the 5th week of pregnancy.

Routine ultrasound during pregnancy

If the pregnancy is proceeding favorably and without any deviations, the woman will be assigned three planned ultrasound sessions during the entire period of bearing the child. The first ultrasound is performed in the first trimester, the second in the second, and the third, respectively, in the third trimester. A planned ultrasound during pregnancy allows you to assess whether everything is going “according to plan”, and, if there are suspicions, it is performed again.

The first scheduled ultrasound serves as a method for diagnosing pregnancy as such, allows you to determine whether there are risks of miscarriage, diagnose “failures” in the development of the fetus at the earliest stages – when all vital organs and systems are being laid down and any deviation is fraught with the development of pathologies.
The second planned ultrasound during pregnancy is prescribed in the second trimester in order to assess the development of the baby, and at the same time – the condition of the placenta. In addition, during the second ultrasound session, it is usually already possible to determine the sex of the future baby.
The third planned ultrasound falls, as you might guess, on the time period of the third trimester. At this stage, the degree of development of the baby, the state of the uteroplacental blood flow and even the presentation of the baby are traditionally examined.

When to do an ultrasound during pregnancy?

The specialist who is monitoring the pregnancy will clearly answer the question of when to do an ultrasound during pregnancy. As a rule, the timing of the ultrasound is determined as follows:

first ultrasound – 10-14 weeks. The pregnancy period and the approximate date of delivery, the number of embryos are determine. The tone of the uterus is assessed. The state of fetal development, the probability of chromosomal abnormalities and developmental defects are also examined. The thickness of the cervical fold (collar zone) is assessed – one of the main markers of Down syndrome;
the second ultrasound – 19-23 weeks. The sex of the baby, the size of the fetus and the correspondence of these indicators to the gestational age are determined. In addition to the fact that the size and growth rate of the fetus are assessed. It is possible to evaluate the development of the baby’s internal organs. In addition, the condition of the placenta, the amount of amniotic fluid are studied. The absence of chromosomal abnormalities is confirmed;
third ultrasound – 32-36 weeks. It is necessary to diagnose late fetal developmental abnormalities that have not manifested themselves before. The size of the fetus is determined, the date of the upcoming birth is specified again. The condition of the fetus and its position before birth are assessed, the possibility of umbilical cord entanglement is excluded.

Is fetal ultrasound harmful during pregnancy?

Most representatives of modern medicine unanimously claim that ultrasound is safe for the fetus and does not cause embryotoxic effects. Their opponents, representatives of various spheres of life, unanimously declare the allegedly monstrous consequences of using an ultrasound machine. In fact, there is information that almost all the “horror stories” are greatly exaggerated and do not have any serious evidence. Yes, ultrasound does cause a slight heating of the body’s cells. But this does not affect the condition and health of the fetus. The connection between the use of ultrasound and various pathologies and anomalies of newborns has not been proven.

However, many question such arguments, saying that if it has not been proven. This does not mean that it does not affect. Based on this, the following judgment would be reasonable. While scientists and doctors are researching this issue, let’s be careful and do not expose ourselves and the baby to ultrasound unnecessarily. But if it is vitally necessary, that is another matter. Because sometimes 10 minutes of examination save the life of a baby.

Do you really need any more arguments? For those who are not convince. We inform you: it has been proven that ultrasound is safe for both the baby and the mother. The radiation that opponents of ultrasound are so afraid of actually lasts less than a minute. The rest of the time the device works for reception.

10-14 weeks. First ultrasound

The first ultrasound examination should be done at 10-14 weeks. Sometimes ultrasound is done before 10 weeks. Most often, this happens because the fact of pregnancy could not be established using a home pregnancy test.
There are also indications for mandatory early (before 10 weeks) ultrasound scanning:

aching pain in the lower abdomen;
probability of multiple pregnancy;
bleeding from the genital tract;
if conception was achieved through assisted reproductive technologies (e.g. IVF);
there were problems with bearing a fetus during a previous pregnancy;
suspicion of a non-viable pregnancy;

Ultrasound in the first trimester is necessary to determine the gestational age, identify various pathologies and possible gynecological diseases.
Early diagnostics are also important. Because if any abnormalities are detect that require termination of pregnancy. The body will suffer minimal damage.
The size of the fetus is only important for determining the gestational age up to the 15th week. Later, hereditary features begin to influence the size of the fetus.

20-24 weeks. Second ultrasound

The next ultrasound scan during a normal pregnancy is performed between the 20th and 24th week. However, if changes in hormone levels were detected during routine tests (weeks 10-12 and 16-18), diagnostics may also be required between the 14th and 20th week.
At this stage, the doctor can more accurately determine whether there are any fetal malformations. The size of the fetus, its organs and systems allows for a more detailed examination and the identification of possible deviations from the norm. It also becomes possible to determine the condition of the placenta and see any abnormalities.

At 22-24 weeks, there is already a high probability of finding out the baby’s sex. Also, at this stage, Dopplerography is performed – an ultrasound examination that detects impaired blood flow in the vessels.

32-34 weeks. Third ultrasound

The next scheduled ultrasound is perform from the 32nd to the 34th week of pregnancy. It Dopplerography – no earlier than a month later.
In the third trimester, diagnostics are also performed to identify fetal malformations. If any malformation is diagnosed, it is determined whether surgical intervention will be necessary immediately after the birth of the child. Sometimes, if the disorder is serious, a decision is made to stimulate labor by administering medications that facilitate the onset of labor.
The goals of the third ultrasound:

determining the position of the fetus in the uterus to plan the tactics of labor management (what faces the exit of the uterus – the pelvis or the head);
determination and assessment of fetal size;
determination of the location of the placenta;
assessment of uteroplacental and fetoplacental blood flow;

If any abnormalities are detected, medical intervention will be necessary to reduce the likelihood of an immature baby being born.
Ultrasound diagnostics is very important for the normal course of pregnancy. It is necessary to monitor how the fetus is developing and whether there are any pathologies. That you will need to take action to eliminate so that your baby is born healthy.