Dream experiences

I was talking with my mother a few years ago when my own children were quite young. I don't recall how or why the subject arose but the conversation became a little odd to say the least.

A little back-ground is in order I think. When I was small, we lived in what was called one of the 'Pit Rows' that is to say, houses in a long line which shared each wall with the neighbour. These houses were built by the Mine owner for his workers to live in and were therefore built fast and cheap. The houses were one room wide with the staircase in the centre of the house. As you can possibly imagine, the stairs were very steep and quite scary for a small child to climb.

Me: I remember a recurring dream that I always had. I was on my back, sort of sliding down the stairs but I was at the height of the bannister, rather than sliding along at stair level. My knees were bent and my head was sort of raised forward so that my back was bent, I was hunched up.
Mother: That's not possible. You can't have dreamed that.

Me: I did, I dreamed it a lot, sometimes every night. It wasn't a scary dream, even though I was obviously falling or sliding down those steep stairs.
Mother: No, I mean it's not possible because when I was pregnant with you, I fell down the stairs, I slid down on my back and the position that you describe would have been the position you were in, inside my stomach...

I've never been able to explain that. It's not a memory, it was a dream not an experience. How on earth could I dream about something that happened to me before I had even been born? Weird? I think so...