I mentioned it off-hand to an ex-girlfriend and was called a sexist (not in an angry/confrontational way, but pretty much dismissed equally off-hand).
This information is the first result when you Google "fertility by age" [0].
This should be mentioned more often, not to be sexist, but so everyone has the complete information, it's way more cruel to allow people to be deluded until their forties just for them to realize one day they can't have children.
[0] https://en.m.wikipedia.org/wiki/Age_and_female_fertility
> While many sources suggest a more dramatic drop at around 35, this is unclear since few studies have been conducted since the nineteenth century. One 2004 study of European women found fertility of the 27–34 and the 35–39 groups had only a four-percent difference.
From the article:
> Women who become pregnant after age 35 are at increased risk for complications that affect the parent and fetus.