The developmental competence of human metaphase I oocytes with delayed maturation in vitro.

OBJECTIVE: To evaluate whether metaphase I (MI) oocytes completing maturation in vitro to metaphase II ("MI-MII oocytes") have similar developmental competence as the sibling metaphase II (MII) oocytes that reached maturity in vivo. DESIGN: Retrospective cohort study. SETTING: Academic medical center. PATIENT(S): A total of 1,124 intracytoplasmic sperm injection (ICSI) cycles from 800 patients at a single academic center between April 2016 and December 2020 with at least 1 MII oocyte immediately after retrieval and at least 1 sibling "MI-MII oocyte" that was retrieved as MI and matured to MII in culture before ICSI were included in the study. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): A total of 7,865 MII and 2,369 sibling MI-MII oocytes retrieved from the same individuals were compared for the fertilization and blastocyst formation rates. For patients who underwent single euploid blastocyst transfers (n = 406), the clinical pregnancy, spontaneous pregnancy loss, and live birth rates were compared between the 2 groups. RESULT(S): The fertilization rate was significantly higher in MII oocytes than in delayed matured MI-MII oocytes (75.9% vs. 56.1%). Similarly, the blastocyst formation rate was higher in embryos derived from MII oocytes than in those from MI-MII oocytes (53.8% vs. 23.9%). The percentage of euploid embryos derived from MII oocytes was significantly higher than that of those from MI-MII oocytes (49.2% vs. 34.7%). Paired comparison of sibling oocytes within the same cycle showed higher developmental competence of the MII oocytes than that of MI-MII oocytes. However, the pregnancy, spontaneous pregnancy loss, and live birth rates after a single euploid blastocyst transfer showed no statistically significant difference between the 2 groups (MII vs. MI-MII group, 65.7% vs. 74.1%, 6.4% vs. 5.0%, and 61.5% vs. 70.0%, respectively). CONCLUSION(S): Compared with oocytes that matured in vivo and were retrieved as MII, the oocytes that were retrieved as MI and matured to MII in vitro before ICSI showed lower developmental competence, including lower fertilization, blastocyst formation, and euploidy rates. However, euploid blastocysts from either cohort resulted in similar live birth rates, indicating that the MI oocytes with delayed maturation can still be useful even though the overall developmental competence was lower than that of their in vivo matured counterparts.

Metabolomic assessment of oocyte viability.

The aim of the current study was to evaluate whether near-infrared (NIR) spectroscopy-generated metabolomic data obtained from oocyte culture samples would correlate with nuclear maturity status and derived embryo development. A total of 412 oocyte culture samples were collected from 43 patient cycles. Metabolomic profiles of metaphase I and II oocytes were obtained by NIR spectroscopy and were significantly different from each other and from profiles of prophase I (germinal vesicle) oocytes (P +/- 0.001 at the 95% confidence interval). Additionally, NIR spectroscopic analysis of culture medium of oocytes that developed to grade A embryos on day 3 demonstrated significantly higher viability indices (0.62 +/- 0.23) than those that developed to grades C/D (0.42 +/- 0.26; P < 0.006); and on day 5 grade A (0.37 +/- 0.20) was also higher than grades C/D (0.14 +/- 0.21; P < 0.02). Metabolomic profiles of oocytes that resulted in pregnancy had higher viability indices (0.87 +/- 0.27) than those that did not (0.44 +/- 0.17; P < 0.0001). The results of the current study demonstrate that metabolomic profiling from spent culture medium of the oocyte is related to nuclear maturity, is able to predict embryo development at day 3 and day 5 stages, and relates to embryo viability.

The value of fast blastocoele re-expansion in the selection of a viable thawed blastocyst for transfer.

OBJECTIVE: To investigate the role of fast blastocoele re-expansion in the selection of viable thawed blastocysts for transfer. DESIGN: Retrospective study. SETTING: Academic assisted reproductive program. PATIENT(S): Transfer cycles were divided into two groups according to the presence or absence of fast re-expanded blastocysts. In group I (124 cycles), all transferred blastocysts had fast re-expanding blastocoele. In group II (113 cycles), no fast re-expanded blastocysts were included in the transfer. INTERVENTION(S): Blastocyst survival was defined as >50% of cells remaining intact after thaw and re-expansion after culture in vitro for 2-4 hours before transfer. Blastocysts with >or=50% re-expansion were designated as fast re-expanded blastocysts. MAIN OUTCOME MEASURE(S): Percentage of blastomere loss immediately after thaw, degree of blastocoele re-expansion, and clinical outcomes (pregnancy and implantation rates). RESULT(S): The rates of survival and fast blastocoele re-expansion of partially intact blastocysts were significantly reduced as compared with fully intact blastocysts. Significantly higher rates of clinical pregnancy (37.1% vs. 16.8%) and implantation (26.7% vs. 11.3%) were obtained when all transferred blastocysts had fast re-expanding blastocoele as compared with those transfers without fast re-expanded blastocysts included. CONCLUSION(S): Our results showed that blastomere loss of thawed blastocyst was associated with a reduced ability to re-expand. As a discriminative morphologic marker of superior embryo viability, a fast re-expanded blastocyst would be given priority for transfer to better utilize the cryopreserved blastocysts.