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Ultrasound: what is it?

L'echography is a non-invasive diagnostic test that is used - among other cases - to monitor the progress of pregnancy. It is carried out with a probe that emits high frequency sound waves, the ultrasound, which allow you to observe the internal parts of an organism without any damage for the patient or, in the case of a pregnancy, for the unborn child.

In fact, ultrasound is used whenever maternal and fetal pathologies are suspected, but also for the normal monitoring of the evolution of gestation.

Read also: The dictionary of pregnancy

Three ultrasound scans are done during a normal pregnancy. The first takes place in the first trimester (5th-13th week), and serves to assess the presence and vitality of the embryo and the regular evolution of gestation, also verifying whether it is single or multiple. This is the only ultrasound in which pregnancy can be correctly dated, possibly correcting the expected date of delivery. Morphological ultrasound will follow (19th-23rd week), which analyzes the anatomy of the unborn child and diagnoses some of the most frequent malformations. Finally, the pregnant woman will undergo an ultrasound of growth (28th-32nd week), which estimates the weight and checks the regular growth of the fetus.

How does it work?

When an ultrasound is performed, a probe is approached on the surface of the area to be monitored (eg the belly during a check for pregnancy) or inside the body. This probe emits ultrasounds that "bounce" against organs and tissues and allow the instrumentation of define a clear image of the inside of the body on a monitor. From the visual analysis of this image it is possible for a doctor to observe the situation and find any anomalies.

An ultrasound can be 

  • Outdoor: the probe moves on the skin (such as ultrasound scans that monitor the development of pregnancy)
  • sustainability: the probe is inserted into the body
  • endoscopic: the probe is connected to a long thin and flexible tube (the endoscope) which is inserted into the body


Preparation before an ultrasound differs according to the type of exam you have to undergo. Usually the norm foresees the maintenance a fasting until the end of the exam or the obligation to drink and do not urinate (this is the case with pelvic ultrasound), but there may be variations.

Nell 'obstetric ultrasound, for example, it is not necessary to go on a complete fasting regime, but some facilities recommend the patient to do not spread oils or ointments on the stomach in the two days preceding the exam. Such ointments could in fact interfere with the instrumentation.

Ultrasound during pregnancy

The guidelines tell us that over a pregnancy normal must be performed at least three obstetric ultrasound scans over the three quarters. Usually the periods indicated range from 11th to 13th week (first quarter), from 19th to 22nd week (second quarter) and from 30esima alla 34esima week (third quarter).

  • La first ultrasound, also called Office serves to know the number of fetuses (this is where the mother will learn about a possible twin birth) as well as the first cardiac and motor activity of the fetus itself. The examination also establishes the terms of delivery.
  • La second ultrasound, the "morphological", establishes with almost absolute certainty the sex of the unborn child, measure the fundamental organs of the fetus and compares them with fetal growth parameters. With the morphology it is also possible to identify any malformations (but not all) and, in the presence of suspected anomalies, the mother will have to undergo an additional ultrasound (second level ultrasound) to analyze the affected organs with greater care.
  • La third ultrasound, called "growth", allows further verification of fetal development and calculates the weight of the unborn child.

FONRI: ISS, MedlinePlus

Questions and answers

How many ultrasound scans need to be done during pregnancy?

The ministry of health arranges at least three obstetric ultrasound scans, one per quarter.

Is ultrasound in pregnancy dangerous?

Ultrasound is not dangerous for either the patient or the fetus,

When do you know the sex of the baby?

The morphological ultrasound (second trimester) establishes the sex of the unborn child with almost absolute certainty.

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