Contrasting Effects of Maternal and Paternal Age on Offspring Intelligence

Both maternal and paternal ages are increasing in the developed world. The average age of mothers at time of childbirth has increased from 26.4 years in 1974 to 29.3 years in 2002, while the average age of fathers has increased from 29.2 years in 1980 to 32.1 years in 2002 [1]. This increase in the average parental age is most likely due to the societal trend for couples to delay starting a family for career or financial reasons. The concept of the female “biological clock” (the effect of increasing maternal age on reducing fertility) is well known and is a source of anxiety for many women [2]. In contrast, the consequences of increasing paternal age on fertility and other adverse reproductive outcomes are rarely discussed [3].