However, if a mistaken diagnosis labels HKαα/αα as a -α3.7 heterozygote and the other parent is a--SEA heterozygote, there is a 25% chance of the offspring having Hb H (intermediate α-thalassemia), prompting the need for informed consent and allowing the pregnant woman to choose whether to undergo prenatal diagnosis. This evidence concerns the gene GSTM1 and thalassemia.