2 years ago I lost 3L of blood from an arterial bleed caused by an episiotomy. I'm giving birth again in 3 months and they want to give me a cannula just in case as soon as I go to hospital. What's the risk if I say no?

32F, 170cm, pre-pregnancy weight of 58kg. I am part of a program in Australia called Midwifery Group Practice (MGP).

I had a traumatic birth with my first and the start of it was when I had unnecessary testing done to "buy time" until my midwife could come back to the hospital due to a birth she attended the night before. The unexpected change to the plan/location and some other factors caused anxiety which resulted in my labour stalling. By the time I gave birth, I had been in labour for 39 hours, pushed for 2 hours, lost 3L of blood through an episiotomy that severed an artery and broke my finger during transition. It was a lot and I have PTSD symptoms that I have been seeing a therapist for.

I'm worried that if I get to the hospital and immediately get cannulated, my labour will stall again and I will get flashbacks. This is my only concern, otherwise I am pro all the medical interventions.

If I say no or wait until my labour is definitely established, what are the risks? If they are only giving me one cannula, does it make much of a difference? They gave me 3 immediately last time when I started bleeding so even if I was cannulated, I would still need more lines?