Post-ovulatory ageing of the human oocyte and embryo failure

We carried out a prospective study of 221 healthy women who were attemptingpregnancy. During the study, women collected daily urine samples and keptdaily records of intercourse. Ovulation and early pregnancy losses werelater identified by immunoassays of urinary human chorionic gonadotrophinand steroid metabolites. We have used these data to examine whether therisk of early pregnancy loss was higher with post-ovulatory ageing of theoocyte. 192 pregnancies were ranked by the probability that the oocytemight have aged before fertilization. There was a statistically significantincrease in the risk of early loss as the likelihood of oocyte ageingincreased (P < 0.05). No similar risk was observed for clinicalmiscarriages. Post- ovulatory ageing of the oocyte prior to fertilizationmay cause early pregnancy failure in humans as it does in several othermammalian species.