In the beginning, Meredith's voice is discussing "transition", specifically saying "There's a stage you go through during child birth and it's the toughest part. It's called the transition stage. You've been pushing so hard and so long that you're exhausted, spent and there's nothing to show for your effort..." But there is no pushing during the transition stage. Transition is the last part of the first stage of labor, just before pushing starts, when the cervix is almost dilated enough for the 2nd stage (pushing) to begin, but not quite. There is often a strong urge to push at this point but the woman is almost always urged NOT to push until she is completely dilated, so as not to risk prolapsing or even tearing the cervix, which can be catastrophic.