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List of the most important ultrasounds in pregnancy. When and why should we do them?

List of the most important ultrasounds in pregnancy. When and why should we do them?

Article reviewed by Dr. Anca Panaitescu, specialist gynecologist, Clinical Hospital Philanthropy

The ultrasound examination is performed routinely during pregnancy, brings very important information about the evolution of pregnancy and is not considered dangerous. Ultrasound uses reflected ultrasound beams to produce a picture of the fetus, placenta and amniotic fluid. These reflected ultrasound beams are captured and rendered as an image on the ultrasound monitor.

The images, which can also be colored, are called sonograms, ultrasounds or scans and can be saved as part of the child's records.

Fetal ultrasound is the safest method of detecting fetal affections and obtaining information about the fetus, such as size and position. Do not use X-rays or other types of radiation that could harm the fetus!

The first ultrasound examination in pregnancy can be done early in week 5 of pregnancy. At this time, the purpose of the ultrasound is to confirm the presence of the pregnancy, to determine the location of the pregnancy (intrauterine or extrauterine) and to confirm the signs of evolution of the pregnancy (the presence of the bladder or Yolk sac, the presence of the fetal pole and the beats of the fetal heart). The sex of the fetus can be determined ultrasound starting with the second trimester of pregnancy.

Fetal ultrasound also helps in the evaluation of fetal development. Different information is obtained during pregnancy, with each trimester, the pregnant woman knows new data about the baby she is expecting.

Ultrasound from the first trimester of pregnancy

confirm the presence, location and evolution of the pregnancy;

detects an eventual multiple pregnancy;

accurately estimates the age of the fetus;

estimates the risk of chromosomal defects, such as Down Syndrome;

identifies congenital malformations that affect the brain or spinal cord;

helps guide procedures such as amniocentesis or chorionic villi removal.

Ultrasound in the second trimester of pregnancy

estimate the age of the fetus (gestational age);

appreciates the size and position of the fetus, the characteristics of the placenta, umbilical cord and amniotic fluid;

guides during procedures such as amniocentesis or umbilical cord blood collection;

can detect congenital malformations and fetal abnormalities.

Ultrasound in the third trimester of pregnancy

the doctor ensures that the fetus grows properly and moves;

the size and position of the fetus, placenta and amniotic fluid are evaluated;

evaluates blood flow to the main fetal blood vessels;

• can detect some malformations that appear later in pregnancy.

Transvaginal ultrasound (which involves the introduction of an ultrasound probe into the vagina near the uterus) is generally performed early in pregnancy to determine gestational age or to detect an ectopic pregnancy; In the second and third trimesters, the transvaginal ultrasound is used to determine the location of the placenta (for example the placenta previa) or in the case of pregnancies with risk of premature birth, to measure the length of the cervix.

How is a fetal ultrasound performed?

How to prepare?

For optimal abdominal ultrasound, the doctor advises you to come with a full bladder. Thus, it is advisable to consume water and other liquids even before performing the test and avoiding urination before the investigation.

Another recommendation that doctors often make before ultrasound is to avoid getting on the belly with moisturizing cream. If a transvaginal ultrasound is required, the bladder should be empty.

Transvaginal ultrasound is better in some situations compared to abdominal ultrasound. The transducer or probe for transvaginal ultrasound is covered with a latex sleeve and a vaginal lubricant and inserted intravaginally. If you have an allergy to latex, tell your doctor before carrying out the investigation.

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For any reason of concern, medical advice is recommended

It is advisable to consult the doctor regarding any cause of concern regarding the need to perform the fetal ultrasound, its risks, the way of accomplishment or the results that are indicated.

How is a fetal ultrasound performed?

A fetal ultrasound is usually performed by a specialist in ultrasound. However, it can be performed by a radiologist or an obstetrician. Fetal ultrasound can be performed in the doctor's office, hospital or clinic. Often it is not necessary to completely remove the clothes, the shirt (or blouse) can be left and removed from the waist or skirt. If the patient wears a dress then it will be covered with paper or cloth.

Abdominal ultrasound and transvaginal ultrasound

Abdominal ultrasound

it is necessary to carry out the investigation with the full bladder. A full bladder helps in transmitting ultrasound beams and pushes the intestines away from the uterus. This results in a clearer ultrasound image;

the pregnant woman cannot urinate until the investigation is performed. However, the doctor will be notified if the bladder is too full and causes discomfort;

in rare cases, if liquids cannot be consumed in sufficient quantity, the bladder will be filled with physiological serum through a flexible tube (urinary catheter);

If the ultrasound is performed in the last part of the pregnancy, a full bladder may not be necessary. Raising the fetus will push the intestines to one side;

the pregnant woman is lying on her back on an examination table. If the pregnant woman is dizzy while lying on the table, the upper body will lift or she will be recommended to the pregnant woman to turn on one side;

a gel is spread on the abdomen;

a small, manual instrument called a transducer or probe will be moved along the abdomen several times. The pregnant woman can look at the monitor to see the image of the fetus during ultrasound. When the investigation is completed clean the gel on the skin. The motion is not recommended until the investigation is completed.

An abdominal ultrasound lasts up to 30-60 minutes. The images and the ultrasound report will be recommended, by the current doctor of pregnancy.

During the abdominal ultrasound, the sensation of pressure in the bladder may be present. The gel can be cold when first applied to the abdomen. It will feel a slight pressure of the transducer when it is moved on the surface of the abdomen.

Transvaginal ultrasound

When performing transvaginal ultrasound, there should normally be no discomfort. A slight pressure can be felt when the transducer is moved into the vagina.

a full bladder is not required;

the patient is lying on the table with slightly raised hips;

a condom of the preservation form will be placed over the vaginal transducer. The transducer is then easily inserted into the vagina and then moved and rotated to adjust the image obtained on the monitor. Some doctors may allow the pregnancy to insert the transducer alone into the vagina. Transvaginal ultrasound usually takes about 15-30 minutes.

The photographic images, the first photos of your child

Saving and printing on paper the ultrasound image makes it possible to use ultrasound as the first photograph of the child. In order to obtain a good quality image, the ultrasound machine requires a higher level of ultrasound and for a longer period of time than normal. Some devices can record the ultrasound exam on you.


There are no known risks associated with performing fetal ultrasound, neither in the mother nor in the fetus. However, anxiety symptoms can occur if pregnancy or malformations are detected in the fetus.


The results of the investigation are not always provided immediately. Complete results are available sometimes in 2 or 3 days.

Normal values

the fetus has the dimensions corresponding to the age;

heart rate is normal corresponding to the age of the fetus;

if the investigation is carried out late during pregnancy, the fetus has a downward position;

the placenta has characteristics and size corresponding to the age of pregnancy and does not cover the cervix;

The uterus contains an adequate amount of amniotic fluid;

no congenital malformations are visualized. (Many minor and major malformations are not readily visible on ultrasound. Also, congenital malformations do not always occur early during pregnancy).

Worrying values

the fetus grows slower than normal, is small in size or underdeveloped for its age;

the fetus is abnormally large for its age;

the fetus is placed in a position other than the one with the head down at the end of pregnancy, for example the position with the buttocks down (pelvic presentation);

congenital malformations;

the placenta covers the cervix (placenta previa);

the uterus contains too much or too little amniotic fluid;

pregnancy develops outside the uterus (ectopic pregnancy);

pregnancy contains abnormal tissue in place of the normal fetus (molar pregnancy);

absence of fetal beatings; this may indicate the death of the fetus.

Many conditions can change the results of fetal ultrasound. The doctor will communicate and explain to the patient any significant abnormal results correlating them with the medical history.

What might influence the results of fetal ultrasound?

Reasons for not recommending the investigation or reducing its value include:

feces or air in the intestine or rectum;
abnormally low amount of amniotic fluid;
some fetal positions;
the inability to stay stretched during the investigation;
a very active girl.

Tags Pregnancy ultrasound First pregnancy ultrasound Transvaginal pregnancy ultrasound Fetal ultrasound 3D pregnancy ultrasound