try getting one of the plastic birthing tanks with the seperate bottom section which has holes in it for the fry to fall through.
if left in with the mother, the chances are she will prob eat most of her young.
if she is a lighter colour you should be able to see through her bodie and see the fry's eyes(tiny black dots) inside her.
once these dots start to get really prominant(sp) then she will be about ready to give birth
once she has had them get her out the birth tank /net b4 she eats them all.