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In mammalian oocytes, the maintenance of meiotic prophase I arrest prior to the surge of LH that stimulates meiotic maturation depends on a high level of cAMP within the oocyte. In mouse and rat, the cAMP is generated in the oocyte, and this requires the activity of a constitutively active, Gs-linked receptor, GPR3 or GPR12, respectively. To examine if human oocyte meiotic arrest depends on a similar pathway, we used RT-PCR and Western blotting to look at whether human oocytes express the same components for maintaining arrest as rodent oocytes. RNA encoding GPR3, but not GPR12, was expressed. RNA encoding adenylate cyclase type 3, which is the major adenylate cyclase required for maintaining meiotic arrest in the mouse oocyte, was also expressed, as was Galphas protein. To determine if this pathway is functional in the human oocyte, we examined the effect of injecting a function-blocking antibody against Galphas on meiotic resumption. This antibody stimulated meiotic resumption of human oocytes that were maintained at the prophase I stage using a phosphodiesterase inhibitor. These results demonstrate that human oocytes maintain meiotic arrest prior to the LH surge using a signaling pathway similar to that of rodent oocytes.

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STUDY QUESTION Does trophectoderm biopsy for preimplantation genetic testing (PGT) increase the risk of obstetric or perinatal complications in frozen–thawed embryo transfer (FET) cycles? SUMMARY ANSWER Trophectoderm biopsy may increase the risk of hypertensive disorders of pregnancy (HDP) in pregnancies following FET cycles. WHAT IS KNOWN ALREADY Trophectoderm biopsy has replaced blastomere biopsy as the standard of care to procure cells for PGT analysis. Recently, there has been concern that trophectoderm biopsy may adversely impact obstetric and perinatal outcomes. Previous studies examining this question are limited by use of inappropriate control groups, small sample size or reporting on data that no longer reflects current IVF practice. STUDY DESIGN, SIZE, DURATION This was a retrospective cohort study conducted at a single university-affiliated fertility center. A total of 756 patients who underwent FET with transfer of previously vitrified blastocysts that had either trophectoderm biopsy or were unbiopsied and resulted in a singleton live birth between 2013 and 2019 were included. PARTICIPANTS/MATERIALS, SETTING, METHODS Obstetric and perinatal outcomes for patients aged 20–44 years who underwent FET with transfer of previously vitrified blastocysts that were either biopsied (n = 241) or unbiopsied (n = 515) were analyzed. Primary outcome was odds of placentation disorders including HDP and rate of fetal growth restriction (FGR). Binary logistic regression was performed to control for potential covariates. MAIN RESULTS AND THE ROLE OF CHANCE The biopsy group was significantly older, had fewer anovulatory patients, was more often nulliparous and had fewer embryos transferred compared to the unbiopsied group. After controlling for potential covariates, the probability of developing HDP was significantly higher in the biopsy group compared with unbiopsied group (adjusted odds ratio (aOR) 1.943, 95% CI 1.072–3.521; P = 0.029).There was no significant difference between groups in the probability of placenta previa or placenta accreta. There was also no significant difference in the rate of FGR (aOR 1.397; 95% CI, 0.815–2.395; P = 0.224) or the proportion of low (aOR 0.603; 95% CI, 0.336–1.084; P = 0.091) or very low (aOR 2.948; 95% CI, 0.613–14.177; P = 0.177) birthweight infants comparing biopsied to unbiopsied groups. LIMITATIONS, REASON FOR CAUTION This was a retrospective study performed at a single fertility center, which may limit the generalizability of our findings. WIDER IMPLICATIONS OF THE FINDINGS Trophectoderm biopsy may increase the risk of HDP in FET cycles, however, a prospective multicenter randomized trial should be performed to confirm these findings. STUDY FUNDING/COMPETING INTEREST(S) No specific funding was obtained for this study. The authors declare no conflict of interest. TRIAL REGISTRATION NUMBER NA.