I have 6 companions and 4 guards and all of them listed in defence and no crash of the game..Pregnancy is definitely broken. Just to be sure I first tried cheating infinite energy and 100 fertility potions, then proceeded to fill the pussies of 20 women from age 18-25 several times. Not a single pregnancy.
Then I looked in the code and found the line where fertility potion is supposed to double the chance and changed it to give 100% chance every time, did the creampies in everyone again - and no pregnancies.
Also if you have a guard and 4 companions when your base gets attacked the game breaks (probably because you can't have 5 defenders).