Pregnancy over 35
While there is a lot of focus on the specific age of 35, nothing makes this age somehow dangerous or risky, a boundary between a low risk and a high risk pregnancy. It is only because the risk of chromosomal abnormalities, such as Trisomy 21 or Down Syndrome, increases with increasing maternal age. That risk rapidly increases year by year, which is why a woman over the age of 35 is considered of "advanced maternal age."
The risk of Down Syndrome for a 16-year-old mother is approximately 1:2400. The risk of Down Syndrome for a 35-year-old mother is approximately 1:250; for a 50-year-old woman it is approximately 1:6.
In an otherwise healthy woman over the age of 35 or even 40, no unusual safety or health concerns exist other than the increasing Down Syndrome risk.