Population studies don't take into account whether or not the moms took good care of themselves or if they received appropriate prenatal care.

http://www.babycenter.com/404_what-are-the-risks-of-having-a-baby-if-im-35-or-older_3127.bc

All of that sounds scary, but population studies don't take into account whether or not the moms took good care of themselves or if they received appropriate prenatal care.