I think it should be the mothers choice.  Personally, I have done it with
some of my children, not with others.  As a pediatric nurse (back in the
dark ages) I appreciated any parent willing to hold or comfort their child
during a proceedure.
I nursed my daughter while her head was being prepared for stitching, and
during the first of the stitching.  She slept the rest of her way through
the hour long process. (the cut was deep) She never once whimpered or cried.
When we again had to go to the ER for stitches (my kids are active) about 8
months later, she had no reason to show fear, and even though I could not
nurse during the stitching this time as it was near her lip, I held her and
she did not cry.  The doctor, the same one both times, was so proud of her
you would have thought it was his idea!
Patty Spanjer, IBCLC
Dalton, GA