Faculty Bibliography

Embryonic mosaicism occurs when two or more cell populations with different genotypes are present within the same embryo. New diagnostic techniques for preimplantation genetic screening (PGS), such as next-generation sequencing, have led to increased reporting of mosaicism. The interpretation of mosaicism is complicated because the transfer of some mosaic embryos has resulted in live births. Mosaic embryos may represent a third category between normal (euploidy) and abnormal (aneuploidy). This category of mosaic embryos may be characterized by decreased implantation and pregnancy potential as well as increased risk of genetic abnormalities and adverse pregnancy outcomes. Euploid embryos should be preferentially transferred over mosaic embryos. Genetic counseling is necessary before the transfer of a mosaic embryo is considered. Certain types of mosaic embryos should be preferentially transferred over others. Transfer of embryos with mosaic trisomies 2, 7, 13, 14, 15, 16, 18, and 21 may pose the most risk of having a child affected with a trisomy syndrome; however, the transfer of embryos with mosaic monosomies or other mosaic trisomies are not devoid of risk. Patients must be counseled about the risk of undetected monosomies or trisomies within a biopsy specimen as well as the risk of intrauterine fetal demise or uniparental disomy with the transfer of mosaic embryos. Until more data are available, patients should be encouraged to undergo another cycle to obtain euploid embryos, when possible, rather than transferring a mosaic embryo.

Pre-implantation genetic diagnosis (PGD) has changed the landscape of clinical genetics by helping families reduce the transmission of monogenic disorders. However, given the high prevalence of embryonic aneuploidy, particularly in patients of advanced reproductive age, unaffected embryos remain at high risk of implantation failure or pregnancy loss due to aneuploidy. 24-chromosome aneuploidy screening has become widely utilized in routine in vitro fertilization (IVF) to pre-select embryos with greater pregnancy potential, but concurrent 24-chromosome aneuploidy screening has not become standard practice in embryos biopsied for PGD. We performed a retrospective cohort study of patients who underwent PGD with or without 24-chromosome aneuploidy screening to explore the value of concurrent screening. Among the PGD + aneuploidy-screened group (n = 355 blastocysts), only 25.6 % of embryos were both Single Gene Disorder (SGD)-negative (or carriers) and euploid; thus the majority of embryos were ineligible for transfer due to the high prevalence of aneuploidy. Despite a young mean age (32.4 +/- 5.9y), 49.9 % of Blastocysts were aneuploid. The majority of patients (53.2 %) had >/=1 blastocyst that was Single Gene Disorder (SGD)-unaffected but aneuploid; without screening, these unaffected but aneuploid embryos would likely have been transferred resulting in implantation failure, pregnancy loss, or a pregnancy affected by chromosomal aneuploidy. Despite the transfer of nearly half the number of embryos in the aneuploidy-screened group (1.1 +/- 0.3 vs. 1.9 +/- 0.6, p < 0.0001), the implantation rate was higher (75 % vs. 53.3 %) and miscarriage rate lower (20 % vs. 40 %) (although not statistically significant). 24-chromosome aneuploidy screening when performed concurrently with PGD provides valuable information for embryo selection, and notably improves single embryo transfer rates.

PURPOSE OF REVIEW: Elective oocyte cryopreservation for deferred childbearing has gained popularity worldwide, commensurate with increased knowledge regarding age-related fertility decline. The purpose of this review is to summarize recent data regarding trends in delayed childbearing, review recent findings surrounding age-related fertility decline, acknowledge significant gaps in knowledge among patients and providers regarding fertility decline and review outcomes following elective oocyte cryopreservation. RECENT FINDINGS: Despite an inevitable decline in fertility and increase in miscarriage with increasing female age, there is a growing worldwide trend to delay childbearing. Patients and providers alike demonstrate large gaps in knowledge surrounding age-related fertility decline. Oocyte cryopreservation is clinically approved for medically indicated fertility preservation, but a growing number of women are using oocyte cryopreservation to defer childbearing and maintain reproductive autonomy. Mounting data support the efficacy and safety of oocyte cryopreservation when used to electively defer childbearing, with recent studies demonstrating rates of euploidy, implantation and live birth rates equivalent to in-vitro fertilization (IVF) with fresh oocytes. SUMMARY: Oocyte cryopreservation provides women with an option to defer childbearing and maintain reproductive autonomy, with IVF success rates on par with fresh IVF. However, it is critical that patients understand the limitations of oocyte cryopreservation. Greater education regarding age-related fertility decline should be geared toward patients and providers to prevent unintended childlessness.

OBJECTIVE: To determine whether undetected aneuploidy contributes to pregnancy loss after transfer of euploid embryos that have undergone array comparative genomic hybridization (aCGH). DESIGN: Case-control study. SETTING: University-based fertility center. PATIENT(S): Cases included 38 patients who underwent frozen euploid ET as determined by aCGH, resulting in miscarriage. Controls included 38 patients who underwent frozen euploid ET as determined by aCGH, resulting in a live birth. INTERVENTION(S): Next-generation sequencing (NGS) protocols were internally validated. Saved amplified DNA samples from the blastocyst trophectoderm biopsies previously diagnosed as euploid by aCGH were reanalyzed using NGS. Cytogenetic reports of the products of conception for 20 of the pregnancies resulting in miscarriage were available for comparison. MAIN OUTCOME MEASURE(S): The incidence of aneuploidy and mosaicism using NGS within embryos resulting in miscarriage and live birth. RESULT(S): Of euploid embryos analyzed by aCGH resulting in miscarriage, 31.6% were mosaic and 5.2% were polyploid by NGS. The rate of chromosomal abnormalities was significantly higher in embryos resulting in miscarriage (36.8%) than in those resulting in live births (15.8%). The rate of mosaicism was twice as high among embryos resulting in miscarriage than those resulting in live birth, but this was not statistically significant. Next-generation sequencing detected more cases of mosaicism than cytogenetic analysis of products of conception. CONCLUSION(S): Undetected aneuploidy may increase the risk of first trimester pregnancy loss. Next-generation sequencing may detect mosaicism and triploidy more frequently than aCGH, which could help to identify embryos at high risk of miscarriage. Mosaic embryos, however, should not be discarded as some can result in live births.

PURPOSE: The aim of this study was to report the results of IVF with trophectoderm biopsy and preimplantation genetic screening (PGS) following delayed intracytoplasmic sperm injection (ICSI). METHODS: Patients undergoing IVF with PGS and delayed ICSI were included in the study. Indications for delayed ICSI included absent or poor fertilization via standard insemination or more than 50 % immature oocytes, noted post-cumulus stripping for standard ICSI procedure. Delayed ICSI was performed the day after retrieval due to absent or poor fertilization. The immature oocytes were kept in extended culture, and if demonstrated maturity, ICSI was performed. Primary outcome included fertilization rate and blastocyst stage formation, defined by the number of blastocysts for biopsy. Secondary outcome included aneuploidy rate and pregnancy outcomes following single thawed euploid embryo transfers (STEET). RESULTS: Sixteen patients with delayed ICSI were included in the study. Twelve were due to poor fertilization and four secondary to immature oocytes. A total of 219 oocytes were retrieved; ten were frozen upon patient request, 168 had standard insemination, and 13 had routine ICSI on the day of retrieval. A total of 129 oocytes underwent delayed ICSI. Sixty-three (49 %) fertilized, 19 (14.7 %) reached blastocysts for biopsy; fivw of which were chromosomally normal (26.3 %). Three patients underwent STEET of a delayed ICSI embryo; all three resulted in live births, including one embryo biopsied on day 8 of development. CONCLUSION: Fertilization failure or an excessive proportion of immature oocytes in an IVF cycle, necessitating delayed ICSI, showed equivalent fertilization and blast formation rates. With the implementation of trophectoderm biopsy and PGS, these embryos can lead to healthy live born babies.