Defence and fear can be spun many ways, just most don't know what they are capable of. I'll give you an example -YOU are walking down a dark street and YOU see 3 mean looking guys headed your way, and it becomes clear that they mean to do you harm! How do you feel?Self-defense is actually irrelevan as you describe it. It's the reasonable FEAR of danger that constitutes self-defense, and the FACT is that any pregnancy can go south at any time. The woman gets to decide what the extent of the risk might be, and whether she will accept the risk.
Now the same senerio, but you are across the street, where no one sees you, and those same three thugs are headed toward someone you love dearly -Now how do you feel?
It goes back to selfishness, if a mom is worried things may go south for her, instead of protecting her baby.