We previously reported that oocyte morphology was associated with embryo quality and viability, suggesting that controlled assessment of oocyte morphology is useful to predict human embryo quality.During intracytoplasmic sperm injection (ICSI), we occasionally observe oocytes with smooth endoplasmic reticulum clusters (sERC) (Otsuki et al, 2004), which are thought to disappear after fertilization and be closely associated with poor prognosis in achieving pregnancy. This study aimed to investigate the developmental potential of oocytes with sERC and their behaviors using time-lapse recording system. Research study We collected the data of 6,765 matured oocytes retrieved after controlled ovarian hyper-stimulation from August 2010 to September 2015. During ICSI, three experienced embryologists noticed oocytes containing vacuole-like structures, which were defined as sERC by their disappearance at the zygote stage. These embryos were incubated and imaged by either high-resolution time-lapse cinematography or EmbryoScope®. Developmental velocity, rate of clinical use in embryo transfer or cryopreservation, and achieving pregnancy were compared between oocytes with [sERC(+)] and without sERC [sERC(-)]. Of the 6,765 mature oocytes, 46 (0.7%) showed sERC(+). The developmental velocity of embryos derived from sERC(+) oocytes was significantly higher than that of sERC(-) oocytes, including the time of 2nd polar body (PB) extrusion, pronuclei (PN) formation, and syngamy from the ICSI procedure (in h: 2.5±0.6 vs. 2.9±1.0, 7.6±2.4 vs. 9.9±3.9, and 20.7±2.2 vs. 23.7±4.5, respectively; P<0.05). The sERC all disappeared by 4.3±1.2 h after ICSI in the period from 2nd PB extrusion to PN formation. The rate of clinical use of sERC(+) oocytes was 80.4% (37/46), of which 6 underwent fresh embryo transfer and 31 were cryopreserved. In total, 15 embryos were transferred (6 fresh embryos, 9 frozen/thawed embryos), the pregnancy rate was 40% (6/15), and miscarriage rate was 33.3% (2/6). Moreover, the live birth rate was 50.0% (3/6) and one is still ongoing. Healthy babies were born from oocytes with sERC(+). This study demonstrated that oocytes with sERC could develop into good quality embryos and achieve successful pregnancy resulting in healthy babies. Further follow-up of the children are clearly needed, and mechanisms of the emergence of sERC and its impact on embryonic development are still under investigation. Detailed studies with molecular biological methods are necessary.

The origin of the pronucleus (PN) in a single PN zygote (1PN), and whether its genome is normal still remains controversial. We recently established a novel method of discriminating between maternally- and paternally-derived PN using immunofluorescence staining and demonstrated the possibility that both the male and female genome could be packed in 1PN in some cases. However, currently analyzing karyotypes is an invasive technique, limiting its clinical application. Therefore, we tried to distinguish between normally-fertilized zygotes and 1PN zygotes by their morphology or developmental behavior. In this study, we used a microscope with time-lapse system to analyze the developmental time course and morphology of human 1PN zygotes, especially parthenogenetic zygotes induced by artificial oocyte activation. Research study. This study used 32 MII oocytes donated between October 2014 and August 2015 by patients who gave informed consent for this study. Fresh or freeze-thawed MII oocytes were activated electronically and the oocytes were observed by EmbryoScope®. We compared the developmental time course and morphology between parthenogenetic zygotes and normal 2PN zygotes fertilized by assisted reproductive technology. There was no difference in the diameter of the PN in parthenogenetic zygotes compared to the female PN in normal fertilized zygotes (28.9 ± 2.2 vs 26.4 ± 2.0 μ m, respectively). There were significant differences between normal 2PN and parthenogenetic zygotes for the time from intracytoplasmic sperm injection or electronic activation to the 2nd polar body (PB) extrusion (3.0 ± 1.7 vs 2.3 ± 0.5 h, respectively), from 2nd PB extrusion to syngamy (20.8 ± 4.1 vs 18.7 ± 2.9 h, respectively), from syngamy to 1st cleavage (3.0 ± 2.3 vs 3.9 ± 1.1 h, respectively), and from 1st cleavage to 2nd cleavage (9.8 ± 4.8 vs 13.6 ± 5.2 h, respectively). In addition, some parthenogenetic zygotes (6 of 21) developed to blastocysts. The time required from electronic activation to 2nd PB extrusion and from 2nd PB extrusion to syngamy in parthenogenetic zygotes was significantly shorter than in normal zygotes. This may be because oocyte activation or decondensation of the sperm nucleus is not required in parthenogenetic zygotes. In addition, the time required from syngamy to 1st cleavage, and from 1st cleavage to 2nd cleavage in parthenogenetic zygotes was significantly longer than in normal embryos. Thus, differences in the time course of embryonic development in activated zygotes could be used to identify the characteristics of parthenogenetic zygotes, even though further studies are needed. Furthermore, although some parthenogenetic zygotes develop to blastocysts, the clinical use of zygotes with 1PN should be questioned.

The pregnancy rate (PR) of assisted reproductive technologies (ART) was calculated as the number of pregnancies divided by the number of embryo transfers (ET) cycles and/or patients treated within a specified period. However, the population of these cycles and/or patients included several unsuitable cases involving cancellation, failed oocyte pick-up (OPU) or ET, and/or freeze-all cycles. Thus, it was difficult to evaluate the actual success rate of ART programs in those couples having continued ET. Considering that the goal of ART is to achieve successful pregnancy, the most important issues on which to evaluate success are 1) the number of ET required for successful pregnancy and 2) the cumulative pregnancy rate (PR) with repeated ET. This study reviewed these data based on the number of ET per couple. Retrospective study based on the ART database in our Reproductive Centre from January 2006 to December 2014. For the 2192 patients participating in our ART programs, we reviewed the individual clinical outcomes of ART, including the number of cycles required to achieve pregnancy, the cumulative number of pregnancies and take-home babies, and the number of ART cancelations. We then revised the data against each couple and their age. Of the 2192 study participants, 81.9% (n = 1797) had ET and 73.8% (n = 1327) achieved successful pregnancy, and of these, 79.1% (n = 1050) achieved successful pregnancy within three ET, 94.7% (n = 1257) within six ET, and 98.5% (n = 1307) within nine ET. The number of patients who experienced cancellation and no ET were 317 and 395, respectively. The revised PR [successful pregnancy (n = 1327) divided by the revised population (n = 1480)] was 89.7%, and of these patients, 95.7% (201/210) were aged under 30 years, 95.9% (523/547) 30-34 years, 88.1% (474/538) 35-39 years, and 71.9% (128/178) were aged 40-44 years. The number of take-home babies in this period was 1171 (65.2%/ET and 88.2%/successful pregnancy). The PR from individual ET cycles was limited and declined dramatically with respect to advanced maternal age (32.6% in < 30 year-olds, 30.9% in 30-34 year-olds, 25.6% in 35-39 year-olds, and 12.1% in 40-44 year-olds). In contrast, the miscarriage rate increased markedly depending on advanced maternal age (14.2% in < 30 year-olds, 17.8% in 30-34 year-olds, 23.0% in 35-39 year-olds, and 38.8% in 40-44 year-olds). This study of revised PR demonstrates clearly that ART provides a great opportunity to achieve successful pregnancy by repeating the ET. To this end, it is crucial to obtain a suitable number of cryopreserved embryos, for both reducing the cost and the psychophysical burden of such techniques, and increasing the expectation of successful pregnancy in participating ART patients.