For couples embarking on a journey toward parenthood, understanding genetic health is a vital step. Chromosomal abnormalities, specifically Trisomy 13 (Patau Syndrome) and Trisomy 18 (Edwards Syndrome), can lead to significant developmental challenges or pregnancy loss. At our center in Istanbul, we utilize advanced Preimplantation Genetic Testing for Aneuploidies (PGT-A) during the IVF treatment process to screen embryos for these conditions before they are transferred to the uterus.
Understanding Trisomy 13 and Trisomy 18
A trisomy occurs when an individual has three copies of a particular chromosome instead of the normal two. This is usually the result of a random error during the formation of the egg or sperm (nondisjunction). While many trisomies result in early miscarriage, Trisomy 13 and 18 are among the few that may progress to later stages of pregnancy or live birth, though they are associated with severe medical complications.
What is Trisomy 13 (Patau Syndrome)?
Trisomy 13 affects approximately 1 in 16,000 live births. It is characterized by severe intellectual disabilities and physical abnormalities in many parts of the body. Common clinical features include heart defects, brain or spinal cord abnormalities, small or poorly developed eyes, and extra fingers or toes. Due to the severity of these health issues, many infants with Trisomy 13 do not survive past their first days or weeks of life.
What is Trisomy 18 (Edwards Syndrome)?
Trisomy 18 occurs in about 1 in 5,000 live births. It is more common than Trisomy 13 but similarly severe. Infants born with Edwards Syndrome often experience slow growth before birth (intrauterine growth retardation) and a low birth weight. They may have heart defects and abnormalities of other organs, as well as a small, abnormally shaped head and clenched fists with overlapping fingers. Like Trisomy 13, the survival rate beyond the first year is unfortunately low.
The Role of PGT-A in IVF
For patients undergoing IVF in Turkey, PGT-A (Preimplantation Genetic Testing for Aneuploidies) offers a way to analyze the chromosomal makeup of embryos. Previously known as PGS (Preimplantation Genetic Screening), this technology allows embryologists to count the number of chromosomes in each embryo.
The process involves several key steps:
- Ovarian Stimulation and Retrieval: Eggs are collected and fertilized in the laboratory.
- Embryo Culture: The embryos are grown to the blastocyst stage (usually day 5 or 6).
- Biopsy: A few cells are carefully removed from the trophectoderm (the part that becomes the placenta).
- Genetic Analysis: The cells are analyzed to see if they contain the correct number of chromosomes (46).
- Selection: Only "euploid" embryos (those with a normal number of chromosomes) are selected for transfer.
Who Should Consider Trisomy Screening?
While trisomies can occur in any pregnancy, certain factors may increase the risk. Screening for Trisomy 13 and 18 through IVF and PGT-A may be particularly beneficial for:
- Advanced Maternal Age: The risk of chromosomal abnormalities increases significantly as a woman ages, particularly after 35.
- History of Recurrent Miscarriage: Many pregnancy losses are caused by chromosomal aneuploidies.
- Previous Trisomy Pregnancy: Couples who have had a previous pregnancy affected by Trisomy 13 or 18 may seek reassurance.
- Multiple Unsuccessful IVF Cycles: Screening helps ensure that failure is not due to chromosomal issues that are invisible to the naked eye.
Why Choose Istanbul for Genetic Screening and IVF?
Istanbul has emerged as a global hub for reproductive medicine, combining world-class laboratory technology with experienced clinical specialists. Turkey offers high-quality medical services at a more accessible price point compared to many Western European or North American countries. Our clinic utilizes Next-Generation Sequencing (NGS), the gold standard for PGT-A, providing the highest possible resolution for detecting trisomies.
It is important to note that while PGT-A significantly reduces the risk of transferring an embryo with Trisomy 13 or 18, it does not guarantee a successful pregnancy or a healthy birth. Success rates depend on various individual factors, including egg quality, uterine receptivity, and the patient's overall health profile.
Combining PGT-A with Other Genetic Tests
In cases where there is a known genetic disorder in the family, PGT-A can be combined with PGT-M (Preimplantation Genetic Testing for Monogenic disorders). While PGT-A looks for the number of chromosomes (like the extra chromosome 13 or 18), PGT-M looks for specific gene mutations like Cystic Fibrosis or Thalassemia.
Frequently Asked Questions
Can PGT-A detect all genetic abnormalities?
PGT-A is designed to detect "aneuploidy," which is an abnormal number of chromosomes (like Trisomy 13, 18, or 21). It is excellent at screening for these specific conditions. However, it cannot detect every possible genetic mutation or tiny structural changes within a chromosome unless specifically targeted via other testing methods.
Does the embryo biopsy damage the baby?
The biopsy is performed by highly skilled embryologists on the trophectoderm, the group of cells that will eventually form the placenta, specifically avoiding the inner cell mass that becomes the fetus. While any procedure carries a minimal risk, studies suggest that when performed by experts, the biopsy does not significantly impact the embryo's development potential.
Is PGT-A 100% accurate?
PGT-A is highly accurate, generally exceeding 98%. However, biological phenomena such as "mosaicism"—where an embryo has a mix of both normal and abnormal cells—can occur. Therefore, prenatal screening (such as NIPT or amniocentesis) is still recommended during pregnancy as a confirmatory measure.