15-25 extremely fertile, not thinking about having children, likely to get pregnant accidently due to not knowing about cycle, not using contraception properly, possible miscarriage/abortion due to lack of steady relationship, not financially secure, not very good jobs, possibly not educated, haven’t seen the world.
25-30 starting a slow decline in fertility, starting to think about children, marriage, settling down, more financial security, better job, possibly seen some of the world. Contraception use until marriage likely.
30-35 fertility is dropping slightly faster, really thinking about children, married, financially secure, have seen some of the world, good job. Limited contraception but properly used.
35-40 fertility has dropped off a cliff, panicking about children if haven’t got them, probably thinking of a sperm donor, adopting, pets, garden or nieces and nephews as substitute.
40-45 fertility rises slightly as women stop thinking it’s possible for them resulting in a rise of menopause babies. Surrogacy, donor eggs if your rich and still desire a biological child.
45+ lose interest in sex and live out your days as a spinster, childless couple or look after others while there at work. If you had kids, look after them.
This is on average and it’s what I have gained from looking at society in general.
Having said all of that I just read this article on BBC and it was quite illuminating.
In case it doesn’t work its how a 65 year old german woman can be 21 weeks pregnant with donor eggs. (She also had one at 55). It also mentions a 66 year old Spanish lady who gave birth in 2006.