She never loses the Barrenness (-100%, net -75%), but starting with 3.15 she gets an automatic +3% Fertility bonus for each previous kid she's had, max +30%. This bonus is only applied once per check, after any other modifiers to the chance.sorry, I wrote it wrong, there are already several children, but I want to increase the chances from 25% to 50% (after the questline)
If one of the MC or her uses an EFP the net chance is (-75+100) 25%. If both use EFPs the net total chance is 50%. Add the kids bonus to those...maxed bonus with one EFP is 55, or 80 with two.