How long labour lasts mostly depends on:
Whether you've had a baby before, and how long ago that was.
Whether you keep upright and move around in labour.
How easily your cervix opens up (dilates).
The strength of your contractions.
Whether you have an epidural.
The position of your baby.
How calm you are - being relaxed can help you to have a shorter labour
http://www.babycentre.co.uk/x1037967/how-long-will-my-labour-last#ixzz40W2xc8Ce