I'm planning to refuse to give my seat to the pregnant woman standing on the train.
That's very selfish! Why are you planning to refuse the pregnant woman?!
There's lots of pregnant women, she isn't special.
Maybe not, but it's still rude to not give up your seat. Especially if the train has rules saying you must, you could get kicked off or banned from the train.
I took my seat because I'm tired, it's not fair for me to have to if there's other people sitting down.
She is going through a really tough process. Just do the right thing and let her sit down and be the bigger person even if nobody else is giving up their seats.