I just had a not so quick experience with fixing terminal miscarriage. As in, miscarriage scene instead of birth, at the end of pregnancy.
I found out in birth_trigger.rb that miscarriage instead of birth happens if value of $game_player.actor.baby_race=="Others". to check the value, launch the game through console.bat and enter "r $game_player.actor.baby_race" into console (this r echoes values in this version of rpgmaker it seems).
for whatever reason I couldn't find a way to directly edit this variable, however, one can just launch the function that randomly sets the fetus race again, that being $game_player.actor.set_baby_race