I haven't always had this fear, as I have obviously not always had children.
I was blessed to find the love of my life when I was 16 years old. We got married when I was 18, and about 6 months later, we found out we were expecting our first child. I was 3 and 1/2 months along, when we miscarried. You know, right after they tell you go buy your baby things, because now you don't have to worry. We had the nursery all set up. I didn 't know it then, but I have lupus which attacked my child and caused the baby's heart to stop working.
I didn't find out about the lupus until the next time I was expecting, and the doctors told me we were going to lose our son at 32 weeks along. The lupus was trying to kill him, too. As it was, he was born with complete AV block of the heart , and got his first pacemaker when he was 9 months old. My youngest son ( definitely not planned, after all that trouble), was born at 34 weeks , but he is healthy.
From all those things you become scared.It grows inside your heart as a small thought , and blooms into reality with all the fear of the worst horror movie you've never seen , but could only imagine. I used to live without fear. I thought I could do anything, and with that never say die mentality of only the young, I ran headlong into anything I wanted. What could hurt me, after all? If I had only known.
So, I guess I have to say that even though I 've realized I'm not invincible, losing my children or leaving them ( if I were to die) too soon, would still be my only fear.
After all, what is public speaking, drowning or nuclear war, compared to a child dying before their parent. That's probably the most terrifying thing I can think of.