You can’t prevent thalassemias because they’re inherited (passed from parents to children through genes). However, prenatal tests can detect these blood disorders before birth.
Family genetic studies may help find out whether people have missing or altered hemoglobin genes that cause thalassemias. (For more information, go to "How Are Thalassemias Diagnosed?")
If you know of family members who have thalassemias and you're thinking of having children, consider talking with your doctor and a genetic counselor. They can help determine your risk for passing the disorder to your children.