Thank you for your question.
If you have to travel at this gestation then maybe train is easier on you. There are several problems you can face, of which using the toilet can be the most difficult and dangerous. There have been reports of women delivering in the toilets and baby falling on the tracks. Needless to say this is very bad for the baby's survival. This is dangerous because often women find it hard to differentiate between pressure caused by stools and pressure caused by the babys head. This is of course an extreme situation.
More common problems are likely due to loss of balance when the train is moving, nausea and early labour (which is the most worrying). You need to warn the TC and be aware of any doctors on the train who you can alert in case of a problem. Travel with sufficient clothes, sanitary wear, gloves etc in case of an emergency on the train.
It would be so much better to avoid the journey altogether.
I'm not sure I have helped you much but I'm afraid there is not much else to say.