No, I don't think they can or will do them whilst you're pregnant. There's no need at all to worry about it until after you give birth - I think there's a period of time that needs to be left afterwards before you can have one.
They don't like to do them during pregnancy unless you've had a previous abnormal result. It simply because the results can be influenced by pregnancy. I had abnormal last time I had a smear done and got my letter for my second last week. I had mine done this time round simply because of my previous results but if you've had a clear result before or its your first they normally get you to put it off until after birth
"I have seen that some are offered them after having a baby or when your 25 whichever is first"
I don't think this is true, as far as I know unless they have any concerns it's always 25 when you are first offered one. Having a baby doesn't mean you need a smear test, it's just if you are due one whilst pregnant you will get offered it afterwards. Hope that makes sense.
Would they do it if you have had abnormal results and treatment before? My cells went from normal to CGIN3 in several months and i had LLETZ to cut them out. They were very close to becoming a cancer. Im anxious in case they redevelop in the 10 odd months of pregnancy and birth, as they grew pretty rapidly last time. Anyone know if theyd do a gentle smear later in the pregnancy?