Occurrence of smooth endoplasmic reticulum aggregates in metaphase II oocytes: relationship with stimulation protocols and outcome of ICSI and IVF cycles

Abstract STUDY QUESTION Is there any association between the appearance of smooth endoplasmic reticulum aggregates (SERa) in oocytes and ovarian stimulation, embryological, clinical neonatal outcomes ICSI IVF cycles? SUMMARY ANSWER A suboptimal prolonged stimulation is detrimental to by inducing occurrence SERa, which reduces reproductive potential oocytes. WHAT IS KNOWN ALREADY Controlled recruits different qualities. Based on current evidence, it was agreed that non-homogeneous cytoplasm may represent normal variability among rather than a dysmorphism with developmental significance. The only exception SERa within ooplasm. Owing lack univocal evidence this literature about safety injecting mechanism responsible for topic still matter debate. DESIGN, SIZE, DURATION retrospective, longitudinal cohort study performed at tertiary level public infertility center. We included 1662 cycles (180 SERa+ 1482 SERa−) from 1129 women (age: 20–44 years) who underwent IVF/ICSI treatments 2012–2019. had least one oocyte cohort. SERa− morphologically unaffected PARTICIPANTS/MATERIALS, SETTING, METHODS collected data clinical, MAIN RESULTS AND THE ROLE OF CHANCE Overall, 347 out 12 436 metaphase II (2.8%) were affected SER. transfers involving embryo. Stimulation length (P = 0.002), serum progesterone 0.004) follicle size 0.046) trigger, number retrieved 0.0001) significantly higher cycles. Fertilization rate < reduced compared counterparts. Embryos lower blastocyst formation embryos 0.059). Statistical analysis according generalized estimating equation model patient demonstrated duration predictive appearance. success cycles, although no differences birthweights or malformations recorded sibling LIMITATIONS, REASONS FOR CAUTION Given discarded our center years originating generally avoided, are largely attributable transfer derived we did not have newborns oocytes, since none resulted progressive pregnancy. WIDER IMPLICATIONS FINDINGS For first time, speculate late-follicular phase elevated caused be resulting negative effects their potential. This raises question whether some regimens could worse others change protocol would reduce possibility producing maturation. In particular, highlight importance correct timing trigger order maximize collection, terms numerosity but also FUNDING/COMPETING INTEREST(S) None. TRIAL REGISTRATION NUMBER N/A.