What are the chances of success for couples performing an IVF cycle with only poor quality day-3 embryos cultured to the blastocyst stage?

Abstract

In recent years, more and more IVF centers have chosen to culture all embryos until the blastocyst stage, in order to increase implantation rates. Therefore, it is important to inform couples of the strategy and to estimate their chances of getting a good quality blastocyst; especially if the entire embryo cohort is of poor quality. The objective of this study was to evaluate the rate of usable blastocysts and the live birth rate, in couples undergoing an IVF/ICSI who obtained only poor quality day-3 (D3) embryos. This retrospective cohort study, carried out between 2012 and 2016, analyzed 59 cycles of IVF/ICSI that resulted in at least one D3 embryo without any high quality embryos. A comparison to a control group comprising 122 cycles with D3 embryos of both good and poor quality was performed. Cycles in which all D3 embryos were of poor quality were included. All embryos were cultured until day 5 or 6 and were either transferred, cryopreserved or discarded. Exclusion criteria were egg donors, patients performing fertility preservation or modified natural cycle IVF. The embryo quality was scored according to the classification of the Istanbul consensus (Alpha / EHSRE 2011). Thus, D3 embryos were considered of poor quality if the blastomeres had a fragmentation rate > 25% (= grade 3 embryos) or if the number of cells was less than 6 (= slow-development embryos). The « usable blastocysts » rate was defined as the ratio of the number of transferred or cryopreserved blastocysts (if Gardner score ≥ 2BB) to the total number of D3 embryos. Blastulation and live birth rates were expressed as a percentage and compared between the groups by the Chi2 test. In a total of 136 poor quality D3 embryos (from 59 patients), the blastulation rate was 23.5% (compared to a mean blastulation rate of 62% in our laboratory), the rate of usable blastocysts was 11.0% and the live birth rate was 26.7% per embryo transfer. The rate of usable blastocysts was significantly lower if they originated from grade 3 embryos compared to slow-development embryos (6.8% vs 24.2%, p = 0.0054). The live birth rates were comparable by origin of blastocysts. Patients were statistically older and had lower anti-Mullerian hormone (AMH) levels than the control group, composed of 270 poor quality D3 embryos. Blastulation rates were statistically lower than in the control group (23.5% vs. 37.4%, p = 0.005). However, the rates of usable blastocysts and rates of live birth did not differ between the two groups. In the control group, the rate of usable blastocysts was also higher for slow-developing embryos compared to grade 3 embryos (16.1% vs 7.7%, p = 0.048). Despite the absence of good quality D3 embryos, a cohort composed entirely of "rejected" embryos can result in a transferable blastocyst and live birth. It appears that the high fragmentation rate of blastomeres is associated with a poorer prognosis than the decreased number of cells on D3. This study could improve the counseling of couples facing this situation.