Thalassemia is a single gene disease, an autosomal recessive disorder. If both parents are carriers, there is a 1/4 chance that his child will be a child with thalassemia major, but there is also a 1/4 chance that both of them will give the good genes to the next generation, a completely normal fetus. There is also a 50/50 chance of being a carrier, just like the parents. Once both parents are found to have the same type of thalassemia, alpha or beta thalassemia, if you are pregnant, you should check the amniotic fluid, chorionic villi, umbilical cord blood, etc. and take the fetal tissue for further diagnosis.