How Do Alpha and Beta Thalassemia Affect Pregnancy?

Thalassemia is a genetic blood disorder that is common in Thailand, caused by abnormalities in hemoglobin production. There are two main types, Alpha vs Beta Thalassemia. An important question for couples planning to have children is how having one or both partners as carriers of this disease could affect pregnancy. Will it be passed down to the child? And what risks does it pose to future offspring?

Basic Understanding of Thalassemia

Thalassemia is an inherited blood disorder that affects hemoglobin, a crucial protein in red blood cells responsible for transporting oxygen throughout the body. When the structure of hemoglobin is defective, red blood cells become fragile, break easily, and have a short lifespan, leading to chronic anemia.
Normally, adult hemoglobin (Hb A) consists of four protein chains: two Alpha chains and two beta chains. However, if the genes responsible for creating one of these chains are defective, hemoglobin production is impaired, resulting in the production of weak and insufficient red blood cells, which is the basis of thalassemia. This condition can be inherited in a recessive manner, meaning that it can be passed on to children.

Carrier vs Patient: What’s the Difference?

Thalassemia exists in two main forms: “carrier” and “patient,” and these conditions impact the body differently, playing a crucial role in family planning. Here’s a breakdown of the differences:

• Carrier (Thalassemia Trait/Minor): A person with a partial gene defect. They generally don’t show symptoms or only have mild anemia. No treatment is necessary, but they can pass the defective gene to their children.
• Patient (Thalassemia Major/Intermedia): A person with a clear gene defect, having inherited the defective gene from both parents. They experience moderate to severe anemia from an early age and require ongoing care, such as regular blood transfusions.

Preimplantation Genetic Testing for inherited diseases before ICSI at VFC Center

Comparison of Alpha VS Beta Thalassemia

As mentioned earlier, thalassemia has two main types. Although both are forms of thalassemia, Alpha and Beta Thalassemia differ significantly in terms of the genes involved and the severity of the condition. These differences can be explained as follows.

Alpha Thalassemia

A defect in the synthesis of the Alpha chain of hemoglobin causes Alpha Thalassemia. The genes responsible for Alpha-globin production consist of four gene loci located on chromosome 16. The severity of the condition depends on the number of these genes that are missing.

• Silent Carrier: One missing gene; usually asymptomatic
• Alpha Trait: Two missing genes; mild anemia may be present
• Hemoglobin H Disease (Hb H Disease): Three missing genes; a moderately to severe condition requiring special medical care
• Severe form (Hydrops Fetalis / Bart’s Hemoglobin): All four genes are missing; the fetus develops severe edema, which typically results in death in utero or shortly after birth

Beta Thalassemia

This condition is caused by impaired synthesis of the beta chain of hemoglobin. The beta-globin genes are located at two loci on chromosome 11. The severity of Beta Thalassemia depends on the specific gene mutation.

Is Beta Thalassemia dangerous? The answer depends on whether the mutation is classified as a major form. If a major mutation is present, the disease is severe and potentially life-threatening, requiring lifelong treatment.

• Beta Trait: One abnormal gene; usually asymptomatic
• Beta-Thalassemia Intermedia: Moderate to severe symptoms; blood transfusions may be required occasionally
• Beta-Thalassemia Major: The most severe form (inheriting abnormal genes from both parents); patients develop severe anemia from early childhood and require regular blood transfusions

Genetic Inheritance of Thalassemia

Thalassemia follows Mendelian inheritance and is primarily an autosomal recessive disorder. If both partners are carriers, whether of the same type or in cases of Alpha vs Beta Thalassemia, there is a 25% chance that their child will inherit a severe form of the disease. The risks for carrier couples can be categorized as follows

Specific Risks for Carrier Couples

• Beta-Thalassemia Carrier Couple: There is a 25% risk that the child will develop Beta-Thalassemia Major, a severe homozygous condition caused by inheriting defective genes from both parents
• Alpha-Thalassemia 1 Carrier Couple: This occurs when two Alpha-globin genes are missing. During pregnancy, there is a 25% risk that the fetus will develop Hb Bart’s Hydrops Fetalis, a severe condition characterized by fetal edema that results in death in utero or immediately after birth. This condition is caused by the absence of all four Alpha-globin genes (Homozygous Alpha-Thalassemia 1)

In addition, mixed carrier couples such as Alpha-Thalassemia combined with Beta Thalassemia, or Beta Thalassemia combined with Hb E, are at risk of having children with complex conditions such as Beta-Thalassemia/Hb E. This is a common form of thalassemia in Thailand and may present with moderate to severe symptoms.

Pre-Conception Screening and Management

The prevention of severe thalassemia can be significantly improved through Preimplantation Genetic Testing before pregnancy. Early identification of inherited blood disorders helps prevent the transmission of serious conditions such as Beta Thalassemia to future children and supports informed reproductive planning.

Preimplantation Genetic Testing

1. Complete Blood Count (CBC): A preliminary blood test used to evaluate red blood cell size and concentration. Carriers often present with smaller-than-normal red blood cells.
2. Hemoglobin Typing / Hemoglobin Electrophoresis: This test identifies the type and quantity of hemoglobin present, helping determine whether an individual is a carrier of Beta Thalassemia, Alpha Thalassemia, or other abnormal hemoglobin variants such as Hb E.
3. DNA Analysis: Performed when blood test results are inconclusive or when confirmation of specific missing gene locations is required, particularly in cases of Alpha Thalassemia.

Preimplantation Genetic Testing for inherited diseases before ICSI at VFC Center

Genetic Counseling

Once screening results are available, couples identified as high risk should undergo genetic counseling with a physician as soon as possible. This process helps couples clearly understand their genetic risks and plan safe reproductive options. Genetic counseling is especially important for couples considering in vitro fertilization (ICSI) combined with embryo screening (PGT-M), which is currently the most effective and reliable method for selecting unaffected embryos.

Planning a Pregnancy Free from Inherited Disorders at VFC Center

If you and your partner are planning to have a child and wish to assess the risk of inherited conditions such as Alpha Thalassemia or Beta Thalassemia, genetic screening and counseling before pregnancy are essential. Early evaluation helps ensure that your child has the best possible chance to grow and develop in good health.
VFC Center (V-Fertility Center) provides comprehensive thalassemia screening, pre-pregnancy genetic testing, and detailed risk assessments conducted by reproductive medicine specialists using advanced diagnostic technology. Our team supports you at every step, offering confidence and clarity throughout your family-planning journey through preimplantation genetic testing.

Article by: Dr. Sorramon Songveeratham

For consultations or appointments, contact:

VFC Center – V-Fertility Center

Hotline: 082-903-2035

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