Research finds sperm quality drops, genetic problems rise as men age

" The number of men ages 35-49 who father children has increased 40 percent since 1980, according to Wyrobek, while the number of fathers under 30 has fallen 20 percent.
"I've tried to encourage men to have kids sooner,'' said Dr. Paul Turek, director of the Male Reproductive Laboratory at UCSF who is familiar with the research although not part of the study team. "This paper reaffirms what I believe." '

Down syndrome also rises with paternal age when partners are both older.http://www.webmd.com/infertility-and-reproduction/news/20030701/dad-age-down-syndrome