I can appreciate the outcome you're trying to achieve. However, as girls have less value than boys in Calradia (girls marry out), may I suggest an alternative?
Let there be no restrictions on pregnancy but for the usual age restrictions and introduce designations, i.e. children go into a pool and the player/ai gets to nominate x number to become heroes (is that what we're calling them?).
For example, in one game, I got 3 daughters and then no more kids even after save scumming for awhile. That's no fun and no good.
Or another alternative is to change how daughters marry out. Let it be part of the negotiation so either boy or girl can be married out and vice versa depending on who's willing to pay.