I had 2 PPH's for 2 different reasons and a birth with no problems between them.

Birth 1 was no problems.
Birth 2 I had a retained placenta and small PPH. Placenta had to be removed manually under GA.
Birth 3 was no problems.
Birth 4 I had a secondary PPH of approx 1.5lt 2 hours post birth. For some reason my uterus relaxed when it needs to stay tight and hard. Possibly the result of fatigue which can happen after a fast and intense labour of less than 2 hours.

My OB was good at dispelling my fears of it happening again should I choose to have bub #5. He said something along the lines of that it is possible it can happen again but it's not a given and he wouldn't be worried so I shouldn't be either