Introduction
Prenatal testing is typically done for screening purposes rather than for diagnostic purposes. Initially, ultrasound-based birth defect screening was created in the 1950s and has grown important in obstetric treatment. These procedures, including serum screening, carrier screening, and ultrasound, are intended to find pregnant people at a high risk of having children with chromosomal abnormalities or other congenital disorders. Although open neural tube abnormalities can be diagnosed with ultrasound, serum screening is only meant to identify women whose pregnancies are at a higher risk. However, with modern technologies and novel research developments, in in-vitro fertilization, doctors can sometimes diagnose genetic disorders in the embryo before it is transferred to the woman's uterus, referred to as Preimplantation genetic diagnosis (PGD). PGD is now widely accessible and might make it possible to identify inherited disorders, such as Thalassemia, even earlier. Preimplantation genetic diagnosis, often performed on blastomeres biopsied from 8-cell stage in vitro fertilized (IVF) embryos, has gained focus recently as it has been reported as an abortion-free procedure. This article discusses the role of PGD in thalassemia prevention.
What Is Thalassemia?
Thalassemia is an autosomal recessive inherited disorder, which means that for the condition to be passed down to the next generation, both parents must be carriers. The oxygen-carrying protein of the red blood cells is called hemoglobin (Hb). Two proteins—an alpha and a beta—make up hemoglobin. The genetic mutations or deletions of hemoglobin genes, which cause the alpha or beta chains to be produced insufficiently or not at all, are the primary cause of Thalassemia. The formation of red blood cells is compromised if the body does not produce enough of either of these two proteins, which results in anemia that manifests in infancy and persists throughout adulthood.
Beta-thalassemia is caused by a point mutation in the splicing site and promoter areas of the beta-globin gene on the chromosome, whereas deletions of alpha-globin genes cause alpha-thalassemia. Thalassemias serve as a prime illustration of disorders that could be diagnosed before implantation in in-vitro fertilization, as their incidence is higher in some Mediterranean and Asian regions while remaining relatively low in other parts of the world.
Regular blood transfusions and folate supplements are the most common treatments for thalassemia major (beta-thalassemia). However, some people, especially children, require bone marrow transplants; others may require chelation therapy to get rid of excess iron in the body. In some nations, prevention initiatives have lowered the prevalence of Thalassemia at birth and may have spared funds for patient care. Such initiatives need careful planning and funding to include public education, carrier screening, genetic counseling to help couples make educated decisions, and the availability of remedies like prenatal diagnosis.
What Is Preimplantation Genetic Diagnosis?
"Preimplantation genetic testing" refers to evaluating embryos before implantation or pregnancy. In many countries, it is common practice to conduct prenatal diagnostic (PND) testing utilizing chorionic villus samples and/or amniocentesis, followed by the termination of any afflicted pregnancies. Therefore, it was advised for couples to talk to their doctor about the hazards and balance their want to know against those concerns. For instance, people should consider being anxious about not knowing the test results or whether being comforted by the knowledge that an anomaly was not discovered.
Fortunately, in this modern era and with advancements in science, an option for avoiding abortion called preimplantation genetic diagnosis (PGD) has been developed. Although various sampling techniques are available in PGD, typically, one or two blastomeres (a cell formed by division of the fertilized egg) are biopsied from the cleavage stage embryos for genetic diagnosis. Pregnancy termination is avoided because the diagnosis occurs before embryo transfer.
However, the biggest issue with PGD is the increased likelihood of a false positive. Following in vitro fertilization, this procedure is carried out by manipulating the embryo to remove a polar body or a single cell from the blastocyst (a fertilized egg on its' 5th or 6th day). The defect can be found before the embryo is transferred, ensuring that only healthy embryos are returned. However, it is advised that all pregnancies created with IVF/PGD should be given the option of confirmatory testing via CVS or amniocentesis.
What Is the Role of Preimplantation Genetic Diagnosis (PGD) In Thalassemia Prevention?
Thalassemia is the most prevalent monogenic disorder (a disorder caused by variations in a single gene) in several nations around the world. Prenatal diagnostic (PND) programs are the best way to reduce the prevalence of this disease. As the most common monogenic disorder in many nations worldwide, Thalassemia could greatly benefit from PGD as an abortion-free diagnosis method. This potent alternative offers significant benefits to patients who do not want to accept the chance of a poor fetus outcome from an abortion following PND.
Additionally, PGD can be used to discover an HLA-compatible newborn (a newborn having the potential to donate cord blood or hematopoietic stem cells for transplantation) to save the life of an affected sibling by combining mutation detection, human leukocyte antigen (HLA) typing, and PGD. As an alternative to PGD, preimplantation HLA typing testing aims to produce pregnancies with unaffected children who are also HLA-matched with the affected sibling already present.
Conclusion
Thalassemia is an inherited blood condition and is characterized by the body producing either an abnormal form or insufficient amounts of hemoglobin. Heart failure brought on by severe Thalassemia might result in early mortality (between the ages of 20 and 30). Thalassemia major causes heart failure and liver issues if left untreated. Additionally, it increases the risk of infection. For couples who want to avoid having their unborn child aborted but are concerned about passing on a known genetic condition to their kid, preimplantation genetic diagnosis (PGD) has become a viable option as it gives high-risk couples a chance to have unaffected children. It's crucial to realize that genetic testing for reproduction isn't always connected to abortion. The studies support that PGD, which offers a sufficient number of embryos without mutations for transfer, is an effective strategy for preventing the birth of affected children with Thalassemia.
