No effect of ovarian stimulation and oocyte yield on euploidy and live birth rates: an analysis of 12 298 trophectoderm biopsies.

STUDY QUESTION: Does ovarian stimulation affect embryo euploidy rates or live birth rates (LBRs) after transfer of euploid embryos? SUMMARY ANSWER: Euploidy rates and LBRs after transfer of euploid embryos are not significantly influenced by gonadotropin dosage, duration of ovarian stimulation, estradiol level, follicle size at ovulation trigger or number of oocytes retrieved, regardless of a woman's age. WHAT IS KNOWN ALREADY: Aneuploidy rates increase steadily with age, reaching >80% in women >42 years old. The goal of ovarian stimulation is to overcome this high aneuploidy rate through the recruitment of several follicles, which increases the likelihood of obtaining a euploid embryo that results in a healthy conceptus. However, several studies have suggested that a high response to stimulation might be embryotoxic and/or increase aneuploidy rates by enhancing abnormal segregation of chromosomes during meiosis. Furthermore, a recent study demonstrated a remarkable difference in euploidy rates, ranging from 39.5 to 82.5%, among young oocyte donors in 42 fertility centres, potentially suggesting an iatrogenic etiology resulting from different stimulation methods. STUDY DESIGN, SIZE, DURATION: This is a retrospective cohort study that included 2230 in vitro fertilisation (IVF) with preimplantation genetic testing for aneuploidy (PGT-A) cycles and 930 frozen-thawed single euploid embryo transfer (FET) cycles, performed in our centre between 2013 and 2017. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 12 298 embryos were analysed for ploidy status. Women were divided into five age groups (<35, 35-37, 38-40, 41-42 and >42 years old). Outcomes were compared between different durations of stimulation (<10, 10-12 and ≥13 days), total gonadotropin dosages (<4000, 4000-6000 and >6000 IU), numbers of oocytes retrieved (<10, 10-19 and ≥20 oocytes), peak estradiol levels (<2000, 2000-3000 and >3000 pg/mL), and sizes of the largest follicle on the day of trigger (<20 and ≥20 mm). MAIN RESULTS AND THE ROLE OF CHANCE: Within the same age group, both euploidy rates and LBRs were comparable between cycles regardless of their differences in total gonadotropin dosage, duration of stimulation, number of oocytes harvested, size of the largest follicles or peak estradiol levels. In the youngest group, (<35 years, n = 3469 embryos), euploidy rates were comparable between cycles with various total gonadotropin dosages (55.6% for <4000 IU, 52.9% for 4000-6000 IU and 62.3% for >6000 IU; P = 0.3), durations of stimulation (54.4% for <10 days, 55.2% for 10-12 days and 60.9% for >12 days; P = 0.2), number of oocytes harvested (59.4% for <10 oocytes, 55.2% for 10-19 oocytes and 53.4% for ≥20 oocytes; P = 0.2), peak estradiol levels (55.7% for E2 < 2000 pg/mL, 55.4% for E2 2000-3000 pg/mL and 54.8% for E2 > 3000 pg/mL; P = 0.9) and sizes of the largest follicle (55.6% for follicles <20 mm and 55.1% for follicles ≥20 mm; P = 0.8). Similarly, in the oldest group (>42 years, n = 1157 embryos), euploidy rates ranged from 8.7% for gonadotropins <4000 IU to 5.1% for gonadotropins >6000 IU (P = 0.3), from 10.8% for <10 days of stimulation to 8.5% for >12 days of stimulation (P = 0.3), from 7.3% for <10 oocytes to 7.4% for ≥20 oocytes (P = 0.4), from 8.8% for E2 < 2000 pg/mL to 7.5% for E2 > 3000 pg/mL (P = 0.8) and from 8.2% for the largest follicle <20 mm to 8.9% for ≥20 mm (P = 0.7). LBRs after single FET were also comparable between these groups. LIMITATIONS, REASONS FOR CAUTION: Although this large study (2230 IVF/PGT-A cycles, 12 298 embryos and 930 single FET cycles) demonstrates the safety of ovarian stimulation in terms of aneuploidy and implantation potential of euploid embryos, a multi-centre study may help to prove the generalisability of our single-centre data. WIDER IMPLICATIONS OF THE FINDINGS: These findings reassure providers and patients that gonadotropin dosage, duration of ovarian stimulation, estradiol level, follicle size at ovulation trigger and number of oocytes retrieved, within certain ranges, do not appear to significantly influence euploidy rates or LBRs, regardless of the woman's age. STUDY FUNDING/COMPETING INTEREST(S): No external funding was received and there are no competing interests to declare. TRIAL REGISTRATION NUMBER: N/A.

A rationale for biopsying embryos reaching the morula stage on Day 6 in women undergoing preimplantation genetic testing for aneuploidy.

STUDY QUESTION: Is there a benefit to assessing ploidy in delayed embryos reaching the morula stage on Day 6 of development? SUMMARY ANSWER: Day-6 morulae should be considered for biopsy in women <40 years old undergoing preimplantation genetic testing for aneuploidy (PGT-A) because they are associated with acceptable, albeit reduced, euploidy and implantation rates (IRs). WHAT IS KNOWN ALREADY: Embryo development and morphology have been shown to correlate with aneuploidy and pregnancy rates. During PGT-A cycles, embryos are biopsied if they reach the blastocyst stage by Day 5 or 6, whereas slow-developing embryos are typically deselected and discarded. Determining the viability of slow-developing embryos is particularly relevant for women undergoing PGT-A who have diminished ovarian reserve and a relatively low blastocyst yield. STUDY DESIGN, SIZE, DURATION: This is a retrospective cohort study that was performed at an academic medical center. Patients who underwent IVF with PGT-A were reviewed for inclusion. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 1615 cycles were reviewed. All cycles which involved a biopsy of a cavitating or compacted morula on Day 6 were included (n = 763). PGT-A was performed using array comparative genomic hybridization. The aneuploidy and implantation of morulae were compared to those of blastocysts originating from the same couples. MAIN RESULTS AND THE ROLE OF CHANCE: The study included 763 cycles in which 1260 morulae and 3014 blastocysts were biopsied. Women were divided into four age groups (<35, 35-37, 38-39 and ≥40 years): the prevalence of aneuploidy was consistently lower among blastocysts (40.3, 50.8, 56 and 78.3%, respectively) than among compacted morulae (68.7, 75.5, 88.9 and 98.1%, respectively) and cavitating morulae (57, 66.4, 81 and 91.6%, respectively) throughout the different age groups (P < 0.001). Of note, the majority of compacted morulae (98.1%) and cavitating morulae (91.6%) were aneuploid in women aged ≥40 years. Compacted and cavitating morulae had significantly higher rates of complex aneuploidy, which involves ≥3 chromosomes, compared with blastocysts (P < 0.001). Furthermore, euploid morulae were associated with a significantly lower IR (28.2 versus 54.6%; P = 0.002) and live birth rate (23.1 versus 55.0%; P = 0.001) compared to euploid blastocysts. LIMITATIONS REASONS FOR CAUTION: This study confirms that Day-6 morulae should not be discarded in young women undergoing PGT-A. However, a potential drawback of biopsying embryos at the morula stage is the inability to distinguish between inner cell mass and trophectoderm cell origin. The sample size of euploid morula transfer cycles in this study was limited. Thus, a larger cohort would be beneficial to validate the reassuring live birth and spontaneous abortion rates reported here. Furthermore, the reproducibility of our findings should be determined at different centers. WIDER IMPLICATIONS OF THE FINDINGS: Although Day-6 morulae are associated with higher aneuploidy rates and lower IRs compared to blastocysts, they still yielded successful pregnancies. Therefore, testing Day-6 morulae should be considered, especially for women <40 years old who are undergoing PGT-A with a small cohort of available blastocysts for biopsy. STUDY FUNDING/COMPETING INTEREST(S): The authors have nothing to disclose. They received no specific funding for this work. TRIAL REGISTRATION NUMBER: N/A.