Obstetric ultrasound

The role of ultrasound and prenatal screening

In modern perinatology, obtaining objective information about the intrauterine state of the fetus is a paramount task. To achieve this goal, prenatal screening is used—a comprehensive examination with clearly defined goals and objectives. The most important rule of screening is that it must be performed within strictly regulated (mandated) gestational timeframes.

The structure of prenatal screening includes the following methods:

• Ultrasound methods: basic echography allowing visualization of anatomical structures.
• Biochemical methods: analysis of specific markers in maternal blood.
• Other auxiliary examinations.

When performing ultrasound diagnostics, the physician must clearly understand the specific goals of the examination. These goals are not universal throughout gestation—they change drastically depending on the trimester. In each trimester, the specialist faces unique tasks in assessing both the fetus itself and the condition of the placenta.

Repeat expert-level ultrasound examination

Despite the high diagnostic value of basic screening, in some cases a more in-depth approach is required. If screening examinations in the first or second trimester reveal a high risk of chromosomal abnormalities (CAs) and/or congenital malformations in a patient, a repeat fetal ultrasound is strictly indicated. Such an examination is classified as expert-level echography.

According to clinical guidelines, the recommendation grade for this appointment is evaluated as C (5).

Performing an expert ultrasound requires special conditions. The location of the examination must be:

• Obstetric medical organizations belonging to the third group (level) of care delivery.
• Specialized medical genetic centers (within the framework of consultative appointments).

A key legal and organizational requirement for such medical institutions is holding a valid license in the specialty of "obstetrics and gynecology". An important clarification is made: the license must be issued excluding assisted reproductive technology (ART) services.

Invasive methods and preimplantation diagnostics

Ultrasound examination is often supplemented by other methods of obtaining objective information. In complex cases, invasive techniques are used, requiring the physician to strictly consider indications, contraindications, and have flawless mastery of the execution technique.

A special place is occupied by invasive methods of preimplantation diagnostics (micromanipulations), used at the stage of obtaining genetic material even before pregnancy occurs. Based on microphotographs, the following precision methods are distinguished:

1. Embryo biopsy: performed at the stage of development when the embryo consists of exactly eight blastomeres. The technique involves the careful extraction of one or several blastomeres using a special micropipette.
2. Polar body biopsy: the method involves extracting the polar body of an oocyte or zygote. The obtained material is sent for subsequent detailed genetic analysis.

Comprehensive approach to pregnant patient evaluation

For a full mastery of the topic of obstetric and perinatal examination, in addition to high-tech ultrasound, one must be proficient in basic clinical skills.

The list of mandatory competencies for a physician includes:

• Examination of a pregnant woman: knowledge of general methods, as well as strict rules and techniques for measuring pelvic dimensions (pelvimetry).
• External obstetric examination: the specialist must clearly define the goals of this examination and be proficient in its practical techniques (palpation).

Only the skillful integration of traditional techniques (external examination, pelvimetry) with modern technologies (ultrasound, biochemical screening) allows for the most objective picture of maternal and fetal status.

Class and exam questions

What else to study on this topic

• General methods for examining a pregnant woman and rules for performing pelvimetry.
• Goals and practical mastery of external obstetric examination techniques.
• Indications, contraindications, and technique for performing invasive diagnostic methods.
• Biochemical and other auxiliary methods of prenatal screening.
• Biopsy of the oocyte and zygote polar body for genetic analysis.

Other topics in the "Additional Topics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.