Correlation between the pronucleus size and the potential for human single pronucleus zygotes to develop into blastocysts : 1PN zygotes with large pronuclei can expect an embryo development to the blastocyst stage that is similar to the development of 2PN zygotes.

PURPOSE: In this study, we examined the correlation between pronucleus size and the potential for human single pronucleus (1PN) zygotes to develop into blastocysts after IVF and ICSI. METHODS: This study included 112 patients who underwent a total of 112 cycles of IVF/ICSI. To evaluate embryo development, 1PN zygotes were compared with 2PN zygotes in the same IVF/ICSI cycle (control cycles) using time-lapse live embryo imaging. To assess the potential for blastocyst formation, cutoff values for pronuclear area and diameter were established through receiver operating characteristic curve analysis, after which 1PN zygotes were classified based on those cutoff values. RESULTS: Among 1PN zygotes cultured to day 5/6, the rate of embryo development was significantly lower than from 2PN zygotes. However, the rates of blastocyst formation and good quality blastocysts from 1PN zygotes with large pronuclear areas (≥ 710 µm2) or diameters (≥ 31 µm) were significantly higher than from 1PN zygotes with smaller pronuclear areas (≤ 509, 510-609, and 610-709 µm2) or diameters (≤ 24, 25-27,and 28-30 µm) (P < 0.01). Moreover, the results for 1PN zygotes with large pronuclei were similar to those for 2PN zygotes. CONCLUSIONS: The developmental potential of 1PN zygotes with large pronuclear areas (≥ 710 µm2) or diameters (31 µm) appears to be similar to that of 2PN zygotes, and measurement of pronuclear area or diameter in 1PN zygotes is a simple, potentially useful, clinical method.

The normality of sperm in an infertile man with ring chromosome 15: a case report.

PURPOSE: The purpose of this report is to analyze the chromosome status and fertilization capability of sperm obtained from an infertile male patient with ring chromosome 15. METHODS: This was a case report at a private in vitro fertilization clinic. A man diagnosed with severe oligozoospermia carrying ring chromosome 15. To evaluate the chromosome status and fertilization capability, sperm from a patient carrying ring chromosome 15 were injected into enucleated mouse oocytes. RESULTS: The karyotypes of motile sperm from a patient carrying ring chromosome 15 were normal, and ring chromosome 15 was not observed in the chromosome spread samples of 1PN. In addition, these motile sperm retained the fertilization capability. However, the fertilization rates decreased (85.2, 76.2, and 64.3%, respectively) along with the decline of the aspect ratio of the sperm head (≥ 1.50, 1.30-1.49, and < 1.30, respectively). CONCLUSIONS: The karyotypes were normal without ring chromosome 15, and motile sperm with a high aspect ratio showed adequate potential for fertilization.