Last year, the CDC published a study that has been tracking the age of first time mothers. The study concluded that the age of first time mothers has increased across every ethnicity, mostly due to the decrease in teen pregnancy since its peak in 1990.
Age during pregnancy can be a factor in calculating a woman's pregnancy risks, specifically if she is 35 or older. These factors include having a baby with Down syndrome, as well as a higher rate of spontaneous miscarriage.
If you would like more information on the risks of advanced maternal age on pregnancy and childbirth, check out this article from Evidence Based Birth. And, as always, discuss your personal risks with your care provider.