Highly educated women with high earning jobs don't really have fewer children. It's the women who are above average educated with above average earning. The first category would be graduate degrees/specialised degrees with an earning above 200K in most parts of America (well above it in the vhcol areas and lower in lcol areas) while the second is those earning 70-120K in most parts of America with a bachelor education or some less wanted graduate degrees (again a bit higher in vhcol areas).
Very high educated well earning women can offload their duties to others even the getting pregnant part these days. Educated women also tend to have a higher desire for large families, I know families with large amounts of engineers/lawyers/doctors where almost all get more than 2 children.