Brother-sister and father-daughter incest is far from a rare occurrence and Weitzel et al (see p 127) are correct to emphasize the need for empathetic support for the involved daughters and brother and sisters. However, we must not lose sight of the children who may, or in fact do, result from such unions.
The women involved are almost invariably young,1 a fact that adds a well-recognized increase in mortality and morbidity among the resulting children. More importantly, progeny of incestuous unions have an inbreeding intensity four times that of first cousin marriage. Data suggest2 that there is a 4% to 5% greater frequency in death plus major congenital defect in children of first cousins compared with control children. In the children of a first cousin marriage, the probability that a child will be homozygous for a specific gene present in one of the grandparents is .0625. In the child
ADAMS MS. Incest: Genetic Considerations. Am J Dis Child. 1978;132(2):124. doi:10.1001/archpedi.1978.02120270022002