The number of retrieved oocytes does not decrease during consecutive gonadotrophin-stimulated IVF cycles.

Abstract

Our aim was to study whether there is a decreasing trend in the number of retrieved oocytes in women who had all undergone at least seven consecutive IVF cycles. A nationwide retrospective cohort study was conducted among women whose first IVF cycle was stimulated with gonadotrophins in The Netherlands between 1983 and 1995. Among these eligible women, we identified all women who had received at least seven consecutive IVF cycles (n = 330). Poisson regression analysis was used to assess the trend in the number of retrieved oocytes over the first six IVF cycles. The unadjusted results showed a slight but non-significant decrease in the number of retrieved oocytes over six IVF cycles. The change in cycle 6 compared with cycle 1 was -0.06 oocytes (5.8% decrease) (P = 0.21). When adjusting for the number of ampoules and the stimulation protocol (fertility drug used combined with use of GnRH agonists), there was a considerable and highly significant decrease from cycle 1 to cycle 6 [change in cycle 6 compared with cycle 1: -0.19 oocytes (17.4% decrease), (P < 0.0001)]. However, when adjusting for age of the women, this decrease almost completely disappeared [change in cycle 6 compared with cycle 1: -0.05 oocytes (5% decrease), (P = 0.50)]. The results suggest that there is no decrease in the number of retrieved oocytes over subsequent cycles when simultaneously accounting for the increasing age of the women, differences in the number of ampoules of gonadotrophins used, type of stimulation protocol and year of IVF treatment.