Best age for a woman to have a successful pregnancy?

This question is just biologically speaking. Please do not include social/religious beliefs or what is morally accepted or not. I know back in the day (1600s) the "normal" age for girls to become pregnant was around their 13-18 years old and at that age they were more likely to have a successful pregnancy than someone in their late 20's. I know the reason this was common was because life expectancy was around 45-50 years of age. So, what is, ultimately, the best age for a woman to have a successful pregnancy (money/career goals set aside)