Does my baby have a higher risk of a birth defect if his father is over 40?

Rarely. The biological clock women face is not as harsh on males.The difference comes with how the sperm is generated vs the egg.New sperm come from stem cells & males can produce healthy sperm well into there 60's, while women are born with all the eggs they will ever have.The egg must survive the years of moms toxic exposures & remain good.Any bad sperm don't swim as well as the good ones.
Slightly higher risk. There is a link between paternal age and some birth defects but the overall risk is low. The current scientific explanation is that DNA changes occur more frequently in sperm as men ages. The risk is low and increases with the age of the man.