4 y.o appearing in the night

[AlishaB]

Hi everyone,
I have a open bed policy. If my kids need to sleep with us, then they are open to. This is especially followed when they have a night-mare, cant get to sleep, or wet the bed, or are sick. (and when DH goes to work overnight.)
This has been working out nicely, and my kids both choose their own rooms more than 90% of the time. However, my 4 year old is starting to wake up at 4am every night and coming into the bed. I wouldn't mind, if he would just go back to sleep, but he tosses and turns and talks and I am getting to the stage in pregnancy where I need *some* sleep to be functional in the morning.
Usually what happens is that I get frustrated after 40 mins and take him back to his room and he falls asleep immediately.
I have asked him why he wakes up, and he doesnt have a clue. He also does not fuss when I take him back to his room...so I dont really get it....
Any suggestions on how to A) keep him sleeping or B) Why he is getting up?
Thanks

[Maluhia]

For us with DD it's that she has to pee, but unelss I put her on the potty she just does not know. Her body wakes her up, and she has no accidents but she just can't fall asleep again until I take her to the potty although she tosses and turns and tries.