People can lose their hearing at any age before they are born，as infants，during childhood，or as【C1】______.Each age of onset has a different name and the deafness may have different【C2】______.
Prenatal deafness means that a baby is born deaf.There are several reasons【C3】______this can happen.If parents are deaf，they may have a deaf baby.There are genes【C4】______deafness that hearing parents can also【C5】______on to their child.Other prenatal【C6】______of deafness can include：accidents；medicine or drugs that the mother takes；illnesses；and genetic syndromes.
Genetic syndromes are a group of characteristics that a child【C7】______from its parents.There are two very common types of genetic syndromes related to deafness.One is Waardenburg’s Syndrome.Its characteristics are very【C8】______.The
person may have pigment （色素）【C9】______：a streak （条纹）of white hair；two different color eyes；or streaks of white in a man’s【C10】______.It is【C11】______to have the physical traits of Waardenburg’s Syndrome but not be deaf.
Usher’s Syndrome is also fairly【C12】______.Children with Usher’s Syndrome are born with a hearing loss and later lose their【C13】______.The first symptoms of this genetic syndrome【C14】______at【C15】______A person with Usher’s Syndrome will【C16】______problems seeing well in the dark.Later，they will lose their peripheral （外围的）vision and see only within a tunnel area in front of them.This is called ’tunnel vision.’Persons may eventually lose more and more of their vision and become blind or【C17】______blind.If you notice that a（n）【C18】______person does not see you when you stand at his or her【C19】______，that person may have this syndrome.The best way to communicate with a person who has Usher’s Syndrome is to stand directly in front and to sign【C20】______.