Because the center for reproductive medicine will choose two test tube embryos for every two couples who have babies born to test tube babies, test the tube embryos in vitro before they are transferred to the mother, according to the basic principles of genetics. This method is commonly known as PGD, and choose the 1 most successful embryo transfer mothers.
Such test-tube embryos that meet the criteria of eugenics and eugenics are selected as follows: some genetic diseases such as X-linked franchise disorders are screened out to occur in the hands of offspring of different genders. Take a man with hemophilia as an example. Usually all his children are normal, while the probability of a girl or all normal or carrying hemophilia genes is half (the carriers of hemophilia genes usually don't get sick). If a woman is a hemophiliac patient, her son will get sick, and her daughter will carry normal or hemophilia genes in half. The basic principles of eugenics such as nutritional deficiency, red green blindness and other genetic diseases are the same as hemophilia. If we grasp the genetic characteristics of these genes, we can carry out genetic examination on the somatic cells of test-tube embryos cultured by test-tube infants, select embryos without pathogenic genes and transfer them to uterus to prevent the birth of children with genetic diseases.
Many genetic diseases can be used to prevent genes from being passed on to future generations, such as thalassemia and congenital stupidity. Two couples deliberately made two different decisions: one agreed to use the third generation baby testing technology to choose a girl; the other was lucky not to use the technology, but also wanted to fight to have a boy, but it is certain that the boy born is still a hemophiliac like the former.