Hi was wondering if anyone can give me any advice..

I have 2 and a half year old twin girls and I am about to tear my hair out..

They have been in their big beds since January...Once they have gone down for the night ( and this happens during the day sleep ) they are forever getting out of bed to " go to the toilet" "I've done a pooh", "I'm thirsty" etc...They sometimes get out of bed up to 20 times for me and Dh to have to put them back..sometimes with a fight..It's like they think it's funny...One of my girls seems to save her pooh for bedtime as an excuse to get out of bed..It has been reducing me to tears the past few days and I have just gotten over a teary as I type this..

We have a scheduled bedtime for them and routine so I'm not sure where we are going wrong or what other strategies we can use..We have a baby due in 9 weeks and I don't think I'm going to be able to handle their antics and a newborn..