After I test:When you say "fertility enhancement potion", do you mean enhanced fertility potion? or regular fertility potion? Because you need the enhanced version, which uses crystallized eggs in the recipe, for it to work. But yes, if you give yourself and her each one, I believe your odds of a successful impregnation go up to 50%, although it might still take more than two attempts (e.g. at 50% chance per attempt, you'd have 93.75% chance after four tries).
Give the fake potion to Jenny first, win the dice and then use the Enhanced Fertility Potion, Jenny is still not pregnant
The second:
I gave Jenny the real fertility potion first, and I used the fertility potion after winning the dice, already making sure Jenny was pregnant (there is a conception animation)