THIS will sound a bit, well, obvious (as in "birth trauma"), although I must explain to you that I was born via Cesarean Section and so did not "exit" my mother normally.
I was terrified of holes in the ground. I'm not speaking gigantic craters or abandoned wells, here. A relatively shallow and small "depression" (maybe five inches deep and eight inches in diameter) would cause me to back up in fear. I have no idea from where this fear derived. I have no memory of having fallen into a hole (in THIS lifetime, anyway). I gradually grew out of this one, although to this day I am afraid of being up on human-engineered high places. I've no problem climbing mountains (going up OR down), but to walk to the middle of a bridge overlooking a very deep gorge and looking over the edge? I crawl back off the bridge on all fours.
I also developed a fear of having blood drawn or IVs inserted and haven't got a clue about THIS, either. Very few people LIKE needles, I realize. I'm not afraid of getting a shot for some reason... it's about the needle in the vein. I actually have to be sedated or my blood pressure sinks so low that I will pass out. There is nothing that can be done -- every trick has been tried. My feet can be elevated way over my head and I'll STILL pass out. Soothing music, calm atmosphere, subliminal suggestions, hypnotherapy... what works is: place one sub-lingual 1 mg Ativan under my tongue and go away for 30 minutes.
Also had a fear of glass getting into soft drinks until about age of eight or nine. I'd take the cap off the bottle and then inspect, inspect, inspect... like an OCD I outgrew.