There is an article in the paper today that reckons it's been found that your blood group affects your chances of conceiving. In particular, women with blood type o, the most common type, had a lower egg count and poorer egg quality in their 30's than those with blood type a. Surely if your blood type affects egg quality then it shouldn't matter if your 20, 30 or 40 cos you've got the same blood regardless of what age you are!