Marriages between relatives significantly increase the likelihood that if they are heterozygous for the same pathological gene, then recessive mutations will go into a homozygous state, which means that the risk of giving birth to a sick child will increase.
At present, the relationship between the risk of having children with Down syndrome and the age of the mother has been proved: 22-40% of children with this disease are born from mothers over the age of 35-40. In parents after 40 years, the incidence of sick children increases dramatically. Having a baby over 35 reduces the risk of having a baby with Down Syndrome.
The main means of combating these diseases is their prevention. Since each person is a carrier of at least several harmful recessive mutations, a network of genetic counseling has been created to prevent hereditary diseases. Also, prenatal diagnosis does not hurt. Women need to take care of their health.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.