IVF was a gigantic step. We didn't realise it at the time; people didn't think it would work that well. We never envisaged that it would expand so dramatically around the world. Ethics keeps moving. What was once seen as dangerous goes on to be seen as within the confines of acceptable risk. Probably the major development in the field will come from something we've never thought about. I think there will be a further expansion of low-cost IVF, especially for women in developing countries who experience social discrimination with infertility. If you remove all the expensive stuff and use low-cost drugs (such as clomiphene) and remove just one or two eggs, and only transfer one embryo, it can be done for less than US$100 (£50).