[Genetic counseling for parents of children with impaired vision].

What is the empirical risk of children being born with a disease or malformation? In healthy families, the parents being normal, the probability is 2 to 4%; when the parents are first cousins, although healthy, it is 5%. Of course, the risk if greater in affected families. When the mother or father is affected and there is no consanguinity, the risk if 20%, but when the parents are first cousins, it is 32.5%. When both parents are affected it is 100%. When the parents are normal but one child is affected, the risk for the other children is 25%. When the mother or father is affected and there is already one child affected, the risk for the other children is 50%. When a grandparent is affected, the risk for the grandchildren is 10%. When an aunt or an uncle is affected, the risk for the nephews and nieces is 7%. With regard to genetic counseling, the parents must understand that no physician can guarantee that a child will be normal. They must also understand that the mendelian risks are the same for each pregnancy. Finally, they must know that for each child there is a 2 to 4% risk of a major congenital anomaly. From the human and psychological point of view, the physician must convince the parents that they are not responsible and that both the husband and the wife may carry pathologic genes, as every individual carries 2 to 10 pathologically recessive genes. Finally, it is not the geneticist's responsibility to impose a decision. Only the parents can decide whether they want more children or not.