The actual method of getting seedbed buff/debuff is not recommended as you will not survive the procedure, probably...
I recommend, alternatively, to eat mutated mushrooms (can be bought from passive goblins), they have a random chance of granting you one stack of SB (up to 10 stacks). I recommend eating from around 40-100 mushooms for 10 stacks.
For getting pregnant and live thought it, the easied way would be to bring enough money with you, sleep on the street till you're near death, buy inn's room key and refresh yourself for one night, then sleep on the street again.