37wks and baby hasn't engaged yet.....?

I'm 37wks today and the midwife said my baby is head down but is sitting 'above the brim' of my cervix - so hasn't quite engaged yet. I am just wondering if this means I can still have a natural labour or will it mean I might need a ceserean? How much time do I have for my babies head to engage and what will the doctors do if my baby stays 'above the brim'?