For example, it is estimated that more than 2 million people in Taiwan carry the gene defect which causes thalassemia. If both the mother and the father are carriers, at each pregnancy there is one chance in four that the child will be completely normal, two chances that it will also be a carrier (usually symptom-free), and one that it will have full-blown thalassemia.
以海洋性貧血為例，全台灣估計有二百萬以上的人口帶有這種遺傳基因，如果夫妻雙方都是海洋性貧血的同型帶因者，每次懷孕有四分之一正常的機會，有二分之一帶因的機會，有四分之一重型海洋性貧血的機會。