Well, no, but in a sense, I kind of was. The ovum already existed and had for <mother's age at the time> years, but the exact sperm did not. I came along too much later for that to have been possible. But my DNA was all there. Just not assembled in the right order yet.

Alternatively, if you believe in reincarnation, I still might have been. I have at least one relative who was there who didn't make it to my birth. Maybe I'm one of them come back.

If that was a conscious choice, that may have been a mistake, but that's another story.