Consanguineous marriage refers to the marriage of direct blood relatives or collateral blood relatives within three generations, that is, people with a common ancestor within three generations intermarry. Starting from the common ancestor, the common ancestor is the first generation, the children of the common ancestor are the second generation, and the children born to the common ancestor belong to the third generation. Individuals within these three generations who engage in intermarriage with each other are considered to be consanguineous marriages.
If cousins get married, their maternal grandmother is the first generation, their mother is the second generation, and the union of cousins is the third generation.
The harm of consanguineous marriage
1. Marriage between close relatives can greatly increase the probability of recessive genetic diseases.
2. The incidence rate of some polygenic genetic diseases in close marriage is higher than that in non close marriage.
3. Children who marry close relatives have a higher early mortality and deformity rate.
4. The offspring of consanguineous marriage will have weaker physical constitution, lighter weight, and shorter stature.