In sug­gest­ing alter­na­tives to the sta­tus quo of high-status women delay­ing child­birth fur­ther and fur­ther, Robin Han­son notes that, unlike advanced pater­nal age, advanced mater­nal age does not cor­re­late with poor learn­ing and social out­comes in chil­dren (in fact, older moth­ers had chil­dren who scored higher).

In all cases, we find evi­dence that chil­dren of older moth­ers have bet­ter out­comes. Not only do chil­dren born to moth­ers in their twen­ties do bet­ter than chil­dren born to teen moth­ers, but chil­dren born to moth­ers in their thir­ties do bet­ter than chil­dren born to moth­ers in their twen­ties. How­ever, when we con­trol for other socioe­co­nomic char­ac­ter­is­tics, such as fam­ily income, parental edu­ca­tion and sin­gle par­ent­hood, the coef­fi­cients on mater­nal age become small and sta­tis­ti­cally insignif­i­cant. The only excep­tion is an index of social out­comes, which is pos­i­tively asso­ci­ated with mater­nal age, even con­trol­ling for socioe­co­nomic fac­tors. For cog­ni­tive out­comes, young moth­er­hood appears to be a marker, not a cause, of poor child outcomes.

That may be, but Han­son also states that women dras­ti­cally under­es­ti­mate their fer­til­ity in later life.

The aver­age woman is born with around 300,000 eggs […] with just 12 per­cent of those eggs remain­ing at the age of 30, and only 3 per­cent left by 40. […]

It is clear that there’s a very rapid loss in the num­ber of eggs avail­able as women age and that the smaller pool of [older] eggs is also more likely to con­tain a higher pro­por­tion of abnor­mal eggs. […]

It’s impor­tant to remem­ber that even 30,000 or so eggs remain­ing at the start of your 30s is still a lot. In addi­tion, the quan­tity and qual­ity of eggs are just two fac­tors affect­ing fer­til­ity: […] lifestyle fac­tors such as stress, smok­ing and being over­weight can have an increas­ingly neg­a­tive impact on fer­til­ity as you get older.