A blastocyst’s implantation potential is linked to its originating oocyte cohort’s blastulation rate: evidence for a cohort effect

To investigate if blastocysts originating from different follicular cohorts have variable implantation rates, adjusted for oocyte age, morphology, and/or ploidy. Retrospective cohort. Academic center. Patients who underwent one or more cycles of autologous ovarian stimulation and in vitro fertilization/intracytoplasmic sperm injection, followed by elective single frozen blastocyst transfer. Blastocyst progression rate of a follicular cohort; defined as the total number of the expanded blastocyst, euploid blastocyst, day 5 blastocyst, or day 5 euploid blastocyst(s) divided by the number of two pronuclei zygote(s). Implantation, defined as serum human chorionic gonadotropin >5 mIU/mL after elective single embryo transfer. A total of 4,292 blastocysts were tracked from their follicular cohort origin to their outcome after elective single embryo transfer. The mean age ± standard deviation of the study population was 36.2 ± 3.6 years old. The median (interquartile range [IQR]) number of oocytes and two pronuclei zygotes per cohort was 17 (12–24) and 11 (8–16), respectively. The median (IQR) number of total expanded blastocysts and day 5 blastocysts per cohort was 6 (4–9) and 2 (1–4), respectively. Preimplantation genetic testing for aneuploidy utilization rate was 63.0%. The median (IQR) number of total euploid blastocysts and day 5 euploid blastocysts were 2 (1–4) and 1 (0–2), respectively. Median (IQR) overall blastocyst progression rate was 60.0% (43.5%–75.0%), euploid blastocyst progression rate 21.4% (13.3%–33.3%), day 5 blastocyst progression rate 20.0% (8.7%–35.2%), and day 5 euploid blastocyst progression rate 9.1% (0.0%–18.2%). All blastocyst progression parameters inversely correlated with increasing age. Multivariable mixed-effects logistic regression analyses, adjusting for oocyte age, number of oocytes retrieved, embryo morphology, and preimplantation genetic testing for aneuploidy status, showed a positive association between overall blastocyst progression (adjusted odds ratio [aOR], 1.04; 95% confidence interval [CI], 1.01–1.08), day 5 blastocyst progression (aOR, 1.05; 95% CI, 1.01–1.09), and day 5 euploid blastocyst progression (aOR, 1.10; 95% CI, 1.03–1.18) and implantation rates. Adjusting for age, oocytes retrieved, morphology, and ploidy status, blastocysts from follicular cohorts with high blastocyst progression rates demonstrate superior implantation potential compared with those from cohorts with lower blastocyst progression rates. This