Huh, I never knew there was research into this.
I was born about six weeks prematurely; my mother was in her 40s when she had me, and they had to deliver me via C-section because my mom had an infection that threatened both me and her. As a result of my early birth, like Beautifulovempty, my lungs were not fully developed, so I was oxygen for a time after birth. My mom describes how I was stuck with needles constantly for various tests.
I had some later problems as an infant and a toddler. I had two surgeries before I was a year old--one to fix a hernia problem; another to remove a cyst from my chest that developed after one of the doctors stuck me with a needle there. I had another surgery when I was 4 years old to correct Strabismus (cross-eyedness); incidentally, I still remember what I was wearing that day (a gray sweatshirt) and what the weather was like (overcast). I was an anxious kid for as long as I can remember, with a whole host of odd phobias, and looking back, I've always been quirky and shy, to put it mildly. I loved traffic signals as a young kid.