Here's what the Internet has to say on the subject

Obtaining precise statistical data on the rate of births with genetic disorders resulting from incest is challenging due to several factors. Reporting on incestuous relationships can be limited due to legal and social stigmas, and data collection may not be comprehensive.

However, some studies and reviews have explored the increased risk of genetic disorders in offspring from consanguineous relationships (relationships involving blood relatives). It's important to note that consanguinity includes relationships beyond what is commonly considered incestuous, such as cousin marriages. Here are some general observations:

Consanguinity and Genetic Disorders:

Studies have suggested that consanguineous relationships are associated with a higher risk of autosomal recessive genetic disorders.

The increased risk is primarily attributed to the higher likelihood of sharing identical copies of deleterious recessive alleles due to a common ancestry.

Specific Rates:

The actual rates vary widely based on factors such as the degree of relatedness, the presence of specific genetic conditions in the family, and the overall genetic health of the individuals involved.

Some studies have reported an increased risk of congenital anomalies and intellectual disabilities in offspring from consanguineous unions.

It's important to approach this topic with sensitivity and recognize that individuals involved in consanguineous relationships may not necessarily have children with genetic disorders. The risks depend on various factors, and not all consanguineous relationships result in adverse outcomes.

For more accurate and up-to-date statistical data, consulting scientific literature, medical databases, or genetic counseling resources is recommended. Genetic counselors can provide personalized information based on the specific genetic and medical history of individuals