as a PP mentioned he is giving you the run around. you have every right to not have the injection and this should be followed in your birth plan. but as HotI mentioned you will need DH (or yourself) to make this very clear in teh birth room and to keep a good eye out as sometimes they can give it to you without you even realising. I recommend that when you pack your birth plan in your hossy bag that you have any wishes such as this written in bold red writing. my midwives advised this as the attending staff find it easier to read highlighted important bits

i had a physiological 3rd stage with DD2 and the placenta took 45 minutes to come down.