Yes contraceptives do fail, I think most of us know or may have experience of that. My first pregnancy occurred when I had a coil. I was in my early twenties and was living with my first husband before we married, certainly not planning a family at that time, that pregnancy resulted in a miscarriage, possibly due to the coil expelling the foetus I had to have a d and c afterwards. My second pregnancy, my older child wasn't planned either, 2nd husband and I had just got together, I wanted to work a bit longer, but my husband said at the time, having two children already from first marriage, "if you want a family you'd better get on with it " My third pregnancy was the only planned one, although I think I had a very early miscarriage in between my children which wasn't planned, but would have been okay for me at that time if it had progressed.