National Rail and all rail journey planners give you the quickest journey even if it meant 6 changes and going by some weird route if it means you arrive 1 minute before a more direct less hassle routing
Depending on the train design, if you stand in a doorway anyone in seat might not be able to see a woman is pregnant.
Saying that, when I was going up to Luton every Monday last year I was the only one in my carriage who gave up their seat for an obviously pregnant woman once.