You may change your mind once you are in labour, particularly if it's a long one like I had (17 hours full on labour).

My partner and I agreed it would be just us in the labour ward.

After a day of prelabour & 6 hours of labour at home and a few at the hospital I realised my partner had called his mum & my parents & they were all on the way to the hospital. He asked if it was OK if his mum could come in. At first I was a bit shocked as we had agreed on having just us. He talked me into it pretty quickly though & I'm actually glad she came in. She gave heaps of support & rubbed my back & stuff & if he needed to have a break (like to go to the loo or have a smoke) it meant I always had someone with me. When my parents arrived they came in and out but when the actual birth happened I got the middy to get everyone except my partner to leave. That worked really well.