William Ledger: Thank you both for your really interesting talks. Can I start the discussion? You have both shown us ways in which ovarian ageing can be accelerated. The question that women ask is how can they slow it down? Are you aware of anything that we, as clinicians, can advise women to do to defer the day when they lose fertility, apart from ‘don't have chemotherapy and don't smoke cigarettes’?

Roger Gosden: I do not know of any genetic condition in humans which seems to be associated with a long-time rescue of primordial follicles. Sixty seems to be pretty close to the limit, maybe very exceptionally beyond that. But if that is the case, that we do not know of any women, say at 70 or 80, who have had any follicles left, that suggests to me the regulation of this process was probably polygenic. That provides greater challenges for any means for slowing down follicle usage. Because in theory we have all of the stocks. We can of course freeze eggs or ovarian tissue, but we want to do it pharmacologically. It is theoretically possible but we do not know all the targets. Steve summarised these targets and there may be more than one target. I wonder whether Steve agrees with me? My impression is that all things have a major inhibitory regulatory load. We see a lot of that in the ovary anyway. That makes sense because the danger for human biology is that you have explosive growth of all these follicles.