Cumulative clinical pregnancy rates privileging elective single embryo transfer: a mathematical model from the quebec (Canada) publicly-funded in vitro fertilisation (IVF) program

Abstract

To estimate the cumulative pregnancy rates in women commencing in vitro fertilisation (IVF) treatment in the new publicly-funded IVF program in Quebec, Canada. Simulation model based on a prospective cohort. Data from fresh IVF cycles performed between August 2010 and February 2011 were submitted to the Canadian ART Register (Quebec) (CARTRQ) by the four assisted reproduction centers in Quebec. Estimation of the cumulative pregnancy rates per cycle started were calculated based on the clinical pregnancy rates of frozen embryo transfer (FET) seen in our clinic during the same time period. From 2403 started IVF cycles, 2247 (93.5%) underwent oocyte retrieval. Embryo transfer was performed in 1,942 (81%) cases, from which 943 (49%) were eSET. The clinical pregnancy rate (CPR) per oocyte retrieval was 26.3%. The multiple pregnancy rate (MPR) was 5.2%; all of which were twins. Frozen embryos were available in 45% of the cases, with significant differences by groups of age (< 35 years: 63.82%, 35-39 years: 41.80%, >40 years: 21.49%; P<0.001). The average number of frozen embryos was 3.8, similarly distributed by groups of age (P=1.0). In our simulation model, cumulative clinical pregnancy rates per oocyte retrieval increased by each cycle of frozen embryo transfer (FET #1: 38%, FET #2: 49.7%, FET #3: 56.9%, FET #4: 64.0%). However it must be noted, only women aged < 35 will have enough frozen embryos to undergo three or more FET. Prior to publicly-funded IVF, the CPR in Quebec was 42.9% with a 27.2% MPR and only 1.6% eSET rate. With the introduction of publicly-funded IVF the eSET rate increased to nearly 50% but a drop in CPR was seen (26.3%) However considering the available frozen embryos the cumulative CPR per oocyte retrieval could be 64%. Differences in the proportion of available frozen embryos according to maternal age are determining factors that influence success.