Reduction in the rate of live births per embryo transferred against both increasing chronological age and increasing basal FSH in a prior spontaneous menstrual cycle. Akande et al. Biological versus chronological ageing of oocytes, distinguishable by raised FSH levels in relation to the success of IVF treatment. Hum Reprod 2002;17:2003-2008. Reproduced by permission of Oxford University Press. FSH, follicle-stimulating hormone.