Congenital Deformities and Chromosomal Disorders: Maternal Versus Paternal Age

Abstract

Aneuploidy (abnormal chromosome number) is the principal hereditary abnormality associated with either parental age or tendencies to originate in 1 parent more often than the other. Risk increases logarithmically with advancing parental age; at age 40, the risk is about 2%. In Down's syndrome, maternal age is a primary factor, but occasionally the father can be implicated. Maternal age is slightly more important than paternal age for other aneuploid syndromes. The anomalies of translocation, inversion, or deletion occur as commonly in males as females and are independent of age. They are an important factor in counseling because of their frequency and because clinically normal individuals can be carriers of genetically balanced anomalies. The risk for producing abnormal offspring can exceed 30%. A history of either several spontaneous abortions or offspring with multiple anomalies is an indication for chromosome analyses on both parents. Among known gene disorders, the severity of X-linked disorders differs in males and females. Gene mutations originate more frequently among males, and the frequency increases with advancing paternal age, particularly implicated are the Marfan syndrome, achondroplasia, hemophilia A, and the Lesch-Nyhan syndrome.