Major reason: to become an educated woman, you pretty much cannot have children before you finish that education, and once you have that education, you want to get the most out of it (and in the US, you have to, as you're probably in serious debt from it), and that usually means working in a full-time job with a rather child-unfriendly schedule and a lot of self-imposed pressure to "establish your career" before taking the risks of motherhood. If you have a career you like, you are more likely to limit the amount of time you're out on maternity leave (if you're in a country that provides decent maternity leave) or get your kids into daycare early in order to get back to the career you hope to preserve (my friends in the US).
There is no better form of birth control for teenage girls and young women than career aspirations.
Source: am an educated woman from the US South, with lots of educated woman friends, few of whom had children before 30, and none of whom work full-time and have more than two - as well as many childhood acquaintances with only high school diplomas and more kids.
Yes this seems to be the story today, both in the west and in some developing countries (e.g. India).
But this was not the historical pattern.
Firstly, it's my understanding that richer families started having fewer kids than poor ones in Victorian times -- about a century too early to be explained by women getting MBAs (or taking the pill).
Secondly, for poorer people before this, I think the main mechanism (in the west) was delayed marriage. (Not famine or disease etc.) Saving up enough money to decently start a household took time, and the community's definition of "decently" set the equilibrium population. See for instance https://en.wikipedia.org/wiki/Western_European_marriage_patt... (and Laslett book above).
There is no better form of birth control for teenage girls and young women than career aspirations.
Source: am an educated woman from the US South, with lots of educated woman friends, few of whom had children before 30, and none of whom work full-time and have more than two - as well as many childhood acquaintances with only high school diplomas and more kids.