Shoulder dystocia and pph

I am 20 weeks pregnant with baby number 3, baby number 2 was born August 2018.. perfect labour.. but all went wrong from when her head was delivered, her shoulders were stuck in my pelvis... She was freed quite quickly and easily but she wasn't breathing after, for a short time and I hemorrhaged and lost 2.5ltrs of blood.

I am terrified of it happening again, my first baby was a text book birth born at 6 pound 10 ounces but baby number 2 was 9 pound 6 ounces, the doctors are pretty certain her size was what caused her to be stuck and for me to have a pph...

Hoping baby number 3 isn't as large as they will give me a c section and I really don't want one, but obviously if push comes to shove I will for the baby's safety, just looking for friendly advice if anyone has been through something similar.

Xxxx