The dawn of a new ice age: social egg freezing.

Given the age-related decline in ovarian reserve and oocyte quality, it is unsurprising the global trend of deferring motherhood has resulted in increased levels of involuntary childlessness. The development of oocyte vitrification, with pregnancy and livebirth rates now comparable to using fresh oocytes, has provided an opportunity to cryopreserve oocytes electively for future use, empowering women with the capacity to delay their childbearing years. While it enhances reproductive autonomy, age-related obstetric complications, economic implications and the risk of unsuccessful future treatment make this a controversial therapeutic option. However, some women have no reasonable alternative, such as single women approaching their late thirties, in whom egg freezing, although not a guarantee against involuntary childlessness, offers hope by extending the window of opportunity to find a partner. Given the upward trend in women electively cryopreserving their eggs, it would appear that a new ice age, from a fertility perspective, is upon us.

Telomere length in human blastocysts.

This is a retrospective study aiming to assess telomere length in human embryos 4 days post fertilization and to determine whether it is correlated to chromosomal ploidy, embryo developmental rate and patient age. Embryos were donated from patients undergoing treatment in the assisted conception unit. Seven couples took part, generating 35 embryos consisting of 1130 cells. Quantitative fluorescent in-situ hybridization (FISH) measured the telomere length of every cell using a pan-telomeric probe. Conventional FISH on six chromosomes was used to assess aneuploidy in the same cells. Maternal and paternal age, referral reason, embryo developmental rate and type of chromosomal error were taken into account. Chromosomally abnormal cells were associated with shorter telomeres than normal cells for embryos that were developmentally slow. Cells produced by women of advanced maternal age and those with a history of repeated miscarriage tended to have substantially shorter telomeres. There was no significant difference in telomere length with respect to the rate of embryo development 5 days post fertilization. Telomeres play an important role in cell division and shorter telomeres may affect embryonic ploidy. Reduced telomere length was associated with aneuploid cells and embryos from women of advanced maternal age.

Distinct pathways drive anterior hypoblast specification in the implanting human embryo.

Development requires coordinated interactions between the epiblast, which generates the embryo proper; the trophectoderm, which generates the placenta; and the hypoblast, which forms both the anterior signalling centre and the yolk sac. These interactions remain poorly understood in human embryogenesis because mechanistic studies have only recently become possible. Here we examine signalling interactions post-implantation using human embryos and stem cell models of the epiblast and hypoblast. We find anterior hypoblast specification is NODAL dependent, as in the mouse. However, while BMP inhibits anterior signalling centre specification in the mouse, it is essential for its maintenance in human. We also find contrasting requirements for BMP in the naive pre-implantation epiblast of mouse and human embryos. Finally, we show that NOTCH signalling is important for human epiblast survival. Our findings of conserved and species-specific factors that drive these early stages of embryonic development highlight the strengths of comparative species studies.

Cytogenetic analysis of human blastocysts with the use of FISH, CGH and aCGH: scientific data and technical evaluation.

BACKGROUND: Recent studies have suggested that biopsy of several trophectoderm (TE) cells from blastocysts followed by comparative genomic hybridization (CGH) analysis might represent an optimal strategy for aneuploidy detection, but few data on accuracy are available. The main question concerns the rate of mosaicism at the blastocyst stage, and to what extent this might cause misdiagnoses. We assessed blastocyst aneuploidy and mosaicism rates and evaluated the accuracy and efficiency of CGH and microarray-CGH (aCGH) for TE analysis. METHODS: A total of 52 blastocysts, from 20 couples, were biopsied and their chromosomes examined by CGH. The remaining cells were spread and tested by fluorescent in situ hybridization (FISH). Of the 52 blastocysts, 20 underwent a second TE biopsy and were tested using aCGH. RESULTS: CGH and aCGH produced results for 98% of TE samples. 42.3% of blastocysts were uniformly euploid, 30% were uniformly aneuploid and 32.4% were mosaic. Of the mosaic embryos, 15.4% were found to be composed of a mixture of different aneuploid cell lines, while 17% contained both normal and aneuploid cells. Mosaic diploid-aneuploid blastocysts with >30% normal cells accounted for <6% of analysed embryos. CONCLUSIONS: Comprehensive chromosome screening and follow-up assessment of large numbers of cells provided a unique insight into the cytogenetics of human blastocysts. Meiotic and post-zygotic errors leading to mosaicism were common. However, most mosaic blastocysts contained no normal cells. Hence, CGH or aCGH TE analysis is an accurate aneuploidy detection tool and may assist in identifying viable euploid embryos with higher implantation potential.

Does the use of calcium ionophore during artificial oocyte activation demonstrate an effect on pregnancy rate? A meta-analysis.

OBJECTIVE: To study the effect, if any, of calcium ionophore as a method of artificial oocyte activation (AOA) on pregnancy outcomes and fertilization rates. DESIGN: Meta-analysis of randomized controlled trials, prospective observational and retrospective trials, case reports, and a case-control trial. SETTING: University-affiliated teaching hospital. PATIENT(S): Infertile couples undergoing fertilization treatment. INTERVENTION(S): Use of calcium ionophore during AOA. MAIN OUTCOME MEASURE(S): Odds ratio (OR) as the summary statistic for binary variables was used. Both a fixed and random effects model were applied. Subgroup analysis using quantitative methodology (risk of bias, metaregression) and graphical comparison (funnel plot) assessed statistical heterogeneity. RESULT(S): Fourteen studies were selected. AOA with calcium ionophore increased the overall clinical pregnancy rate (per ET; OR = 3.48; 95% confidence interval [CI], 1.65-7.37) and the live birth rate (OR = 3.33; 95% CI, 1.50-7.39). This effect of adding calcium ionophore was further demonstrated with fertilization, cleavage, blastocyst, and implantation rates. Subgroup analysis further supported our findings (studies where n > 10 in both arms; random and fixed effects models). A metaregression (beta = -.145) found that as the quality of the study increases, the effect of calcium ionophore is significantly more pronounced with regards to overall pregnancy rate. CONCLUSION(S): AOA with calcium ionophore treatment after intracytoplasmic sperm injection (ICSI) results in a statistically significant improvement in fertilization, cleavage, blastulation, and implantation rates, as well as overall pregnancy and live-birth rates. The conclusion of this systematic review, demonstrating a strong effect of calcium ionophore use, is reassuring and promising, particularly for couples for whom ICSI alone yields poor fertilization rates.

Male and female meiotic behaviour of an intrachromosomal insertion determined by preimplantation genetic diagnosis.

BACKGROUND: Two related family members, a female and a male balanced carrier of an intrachromosomal insertion on chromosome 7 were referred to our centre for preimplantation genetic diagnosis. This presented a rare opportunity to investigate the behaviour of the insertion chromosome during meiosis in two related carriers. The aim of this study was to carry out a detailed genetic analysis of the preimplantation embryos that were generated from the three treatment cycles for the male and two for the female carrier.Patients underwent in vitro fertilization and on day 3, 22 embryos from the female carrier and 19 embryos from the male carrier were biopsied and cells analysed by fluorescent in situ hybridization. Follow up analysis of 29 untransferred embryos was also performed for confirmation of the diagnosis and to obtain information on meiotic and mitotic outcome. RESULTS: In this study, the female carrier produced more than twice as many chromosomally balanced embryos as the male (76.5% vs. 36%), and two pregnancies were achieved for her. Follow up analysis showed that the male carrier had produced more highly abnormal embryos than the female (25% and 15% respectively) and no pregnancies occurred for the male carrier and his partner. CONCLUSION: This study compares how an intrachromosomal insertion has behaved in the meiotic and preimplantation stages of development in sibling male and female carriers. It confirms that PGD is an appropriate treatment in such cases. Reasons for the differing outcome for the two carriers are discussed.

Meiotic and mitotic behaviour of a ring/deleted chromosome 22 in human embryos determined by preimplantation genetic diagnosis for a maternal carrier.

BACKGROUND: Ring chromosomes are normally associated with developmental anomalies and are rarely inherited. An exception to this rule is provided by deletion/ring cases. We were provided with a unique opportunity to investigate the meiotic segregation at oogenesis in a woman who is a carrier of a deleted/ring 22 chromosome. The couple requested preimplantation genetic diagnosis (PGD) following the birth of a son with a mosaic karyotype.The couple underwent two cycles of PGD. Studies were performed on lymphocytes, single embryonic cells removed from 3 day-old embryos and un-transferred embryos. Analysis was carried out using fluorescence in situ hybridisation (FISH) with specific probe sets in two rounds of hybridization. RESULTS: In total, 12 embryos were biopsied, and follow up information was obtained for 10 embryos. No embryos were completely normal or balanced for chromosome 22 by day 5. There was only one embryo diagnosed as balanced of 12 biopsied but that accumulated postzygotic errors by day 5. Three oocytes apparently had a balanced chromosome 22 complement but all had the deleted and the ring 22 and not the intact chromosome 22. After fertilisation all the embryos accumulated postzygotic errors for chromosome 22. CONCLUSION: The study of the preimplantation embryos in this case provided a rare and significant chance to study and understand the phenomena associated with this unusual type of anomaly during meiosis and in the earliest stages of development. It is the first reported PGD attempt for a ring chromosome abnormality.