Unplanned Parenthoodâ€‹ is part of the quest Forging Alliances.
Once you completed Pose as Bebe's Boyfrend go and talk to Anne to start this quest. She will take you back to the headquarters where you will be given more errands to run.
Now you need to dress up as a girl and go to Unplanned Parenthood downtown. Talk to the receptionist, and then go though the door on the right. Keep going until when you find your operation room. After trying to get an abortion, you break free. Take a medical uniform from a drawer and put them on. Go o the record room and open up the 2013 records to initiate a cutscene.
Use Gnome Dust to shrink yourself, and then go through the mouse hole in the wall. Shoot at the pipes to get the army to attack the rats and gnomes or you fight tem yourself if necessary. Proceed to the right under the floor, then use the fart on the flames to clear obstacles. You will get to another operation room. Grow back to your normal size and then a cutscene will start. Perform an abortion on Randy now and then head outside.
Nazi zombie baby foetuses are attacking, fight your way to the left and then shrink yourself to climb up the gauze. Then shoot at the grate and use that as a ladder. Fight Nazi zombie rats along the way and proceed into another air vent.
Move to the right through the air vent until you get to a partially opened vent, then hop out here and shoot at the grenade in the soldier's hand. Walk through the cracks in the wall (shrink yourself) to get out of the wall, and grow back to full size. Ask Stan to be your partner, and use his buddy command on the chain gun. Fight your way forward until when you find the biggest Nazi Zombie foetus. As you fighting, first take out the umbilical cord that provide health them and then finish them off. Head back to Annie outside of City Hall.