Prenatal screening What we need to know

29.08.2022

Table of Contents

The purpose of prenatal screening is early assessment of the risk of development of various pathologies of the fetus and determination of the risk of pregnancy-related complications for the mother. Screening performed in the first trimester of pregnancy allows preventive measures to be taken to avoid some pathologies of the fetus and mother and related complications.

Based on all of the above, effective prenatal screening should be characterized by speed, accuracy and reliable results. It is also important to make a thorough risk assessment, based on the results of multifaceted examinations and a summary of other health factors (ultrasound examination, biochemical parameters, maternal history).

Early diagnostics is called screening in the language of medicine, and studies are divided into two main segments:

Ultrasound screening - Includes scheduled whole during pregnancy (at least 5 times) to conduct ultrasound examinations.
Laboratory screening - includes planned tests, which are carried out as part of planned visits to the gynecologist, mainly in the first trimester of pregnancy.

Laboratory screening has two main tasks:

1. Through prenatal testing, to detect conditions in the mother's body, under the influence of which the correct development of the embryo/fetus may be disturbed.
2. To determine the probability of the presence of fetal malformations (genetic syndromes: Down, Patau, Edwards, Turner, etc.), for which the so-called Double and triple tests. Also new generation non-invasive prenatal tests called NIPT.

Laboratory screening includes:

What types of prenatal testing are available?

There are two main types of tests available to prevent fetal syndromes during pregnancy (prenatal period): screening tests and diagnostic tests. Screening and diagnostic tests determine whether the fetus has a low or high chance of developing various syndromes, such as:

Autosomal aneuploidy - Down syndrome, Edwards syndrome, Patau's syndrome.
Aneuploidy of sex chromosomes - Turner Syndrome, Triple X syndrome, Klinefelter syndrome, Jacobs syndrome, XXYY syndrome.
microdeletions - DiGeorge syndrome, 1p36 deletion syndrome, Smith Magen syndrome, Wolf-Hirschhorn syndrome.
Monogenic diseases.

If screening tests show that you are at high risk of having a baby with one of the syndromes, it is recommended that you also have a diagnostic test to determine if the fetus has a genetic disorder.

Screening tests – A prenatal screening test can determine if your baby is more or less likely to have birth defects, many of which are genetic disorders. These tests include blood tests, specific ultrasounds, and prenatal cell-free DNA screening.

Diagnostic tests – After the screening tests, the final answer is given by a diagnostic test that examines the genetic material of the fetus and therefore can determine whether the fetus has a genetic disorder. Invasive and non-invasive prenatal diagnostic tests ((NIPT) Verasiti, Veragen) It is the only, safe and effective way to confirm the diagnostics. Be aware that some diagnostic tests, such as chorionic villus sampling and amniocentesis, carry a small risk of miscarriage.

As for genetic diagnostics methods (both during pregnancy and in children, non-pregnant women, men), it is used to diagnose either genetic (caused by a single gene change) or chromosomal (change in the number or structure of chromosomes) diseases.

Genetic tests may help:

in the diagnostics of diseases directly caused by mutations in individual genes. Sickle cell disease is one such example.
In the diagnostics of diseases caused by chromosomal abnormalities, usually the addition or loss (deletion) of an entire chromosome, such as Down syndrome or trisomy 18.
Identifying gene changes that may increase the risk of developing the disease, such as the BRCA mutation, which is associated with a higher incidence of breast cancer.
Determining whether someone carries a gene associated with a disease. Carriers may not show any signs of the disease, but have the ability to pass the mutation on to their biological children.