Prenatal Screening Program
The program’s objective is the timely diagnosis of chromosomal abnormalities in the foetus and is offered to all women in their first trimester of pregnancy. The test is partly based on the measurement of maternal blood biochemical markers from a sample taken from the pregnant woman. These blood samples are collected by all the gynaecologists in Cyprus and subsequently sent to the Center’s Clinical Lab whereby the blood measurements are made. The blood results, together with ultrasonographic measurements of the foetus, specifically the nuchal translucency or NT, and the maternal age are finally used to calculate the chromosomal abnormality risk associated with the foetus. The most commonly occurring chromosomal abnormality is Trisomy 21, otherwise known as Down’s Syndrome. The risk given through this screening test is the most relevant piece of information in helping the parents decide whether they will need prenatal diagnostic testing.
The expectant mother visits her physician during the first trimester of pregnancy. The gynecologist completes the special form and takes a small blood sample from the mother.
The laboratory of the Center for Preventive Pediatrics “Americos Argyriou” performs blood tests and forwards the results to the gynecologist.
The combination of blood test results and ultrasound measurements provides the final risk assessment for chromosomal and other abnormalities. Based on the results, the attending physician will offer appropriate guidance.
Most pregnant women will give birth to a healthy baby. However, about 3% of pregnancies will result in a child being born with an anatomical abnormality or a congenital malformation. Prenatal screening programs aim to reduce this risk. These abnormalities are due to damage to the chromosomes or the genes of the fetus (the elements that determine development and health), which occur randomly at conception or due to hereditary causes.
Among these genetic abnormalities are syndromes such as Trisomy 21, Trisomy 18, and Trisomy 13, which are examined by the Prenatal Screening Program of the Center for Preventive Pediatrics “Americos Argyriou”.
The functions of the human body and its physical characteristics are controlled by chromosomes, which are structures in the cell nucleus that carry genetic information. Each chromosome contains hundreds of genes, each responsible for a specific function. All our cells contain 46 chromosomes (arranged in pairs), except for the egg and sperm cells, which each contain 23 chromosomes. At conception, the egg and sperm unite to form the embryo, which receives 23 chromosomes from each parent, making up the normal total of 46.
If, for any reason, an embryo has more or fewer than 46 chromosomes, deviations occur that affect its development and bodily functions. The most well-known deviation in the general population is Trisomy 21 (Down’s syndrome). This condition is caused by the presence of an extra chromosome at position 21, hence the name Trisomy 21.
All couples have a possibility of giving birth to a child with a chromosomal abnormality. This probability increases with the mother’s age.
The diagnosis of chromosomal abnormalities is achieved through cytogenetic testing performed after the 10th week of pregnancy. Since this method is invasive, it carries a miscarriage risk of up to 1%. For this reason, it is offered only to women who are found to have an increased risk of chromosomal abnormalities through the initial screening process described below.
- The detection of chromosomal abnormalities is based on the combination of blood test results and ultrasound measurements, along with the mother’s age.
- The first-trimester ultrasound includes a detailed examination of the fetus.
If the result shows increased risk, the expectant mother’s physician will provide counseling and recommend further testing. Low-risk results mean the likelihood of chromosomal abnormality is reduced. However, for a definitive diagnosis of chromosomal or other abnormalities, the mother must undergo an invasive procedure such as amniocentesis or chorionic villus sampling (CVS).