Human Embryo Growth Research Articles

P-135 No difference in morphokinetic patterns between male and female preimplantation embryos

Abstract Study question Do morphokinetic parameters vary between male and female preimplantation embryos? Summary answer We observed no significant differences in morphokinetic characteristics between male and female preimplantation embryos What is known already Studies across various mammalian species, including humans, suggest that male and female embryos differ in their gene expression and metabolic phenotypes. These variations may inherently affect the timing and duration of key preimplantation events. In the context of ART, such developmental differences may ultimately bias embryo selection, leading to an unbalanced sex ratio in the resulting offspring. To date, only a few studies have explored the relationship between morphokinetic patterns and human embryo sex. While some suggest subtle sex-specific variations in human embryo growth dynamics, results have been conflicting and currently no clear consensus has been reached. Study design, size, duration Retrospective study of morphokinetic data obtained from 175 preimplantation embryos. The study included 175 cycles performed at two IVF centers, between March 2018 and June 2021. Only fresh oocyte donation cycles using intracytoplasmic sperm injection (ICSI) and fresh single embryo transfer (SET) were assessed. Sex of the embryos was obtained from live birth data. Overall, our analysis included 92 female and 83 male embryos. Participants/materials, setting, methods All embryos were cultured in a timelapse incubator in standardized conditions. The morphokinetic parameters assessed included: time to pronuclear fading (tPNf), times to 2–5 cells (t2, t3, t4, t5), time to 8 cells (t8), time to start of blastulation (tSB) and time to full blastocyst stage (tB). All parameters were measured in hours post insemination (hpi). A two-tailed Student’s t-test was used to compare morphokinetics between embryo sexes. A p<0.05 was considered statistically significant. Main results and the role of chance We observed no significant differences in morphokinetic parameters when comparing cycles resulting in female vs. male live births: tPNf (21.8 ± 3.3 vs. 22.3 ± 3.4 hpi; p > 0.39); t2 (24.6 ± 2.5 vs. 25.0 ± 2.5 hpi; p > 0.34); t3 (35.3 ± 3.3 vs. 35.8 ± 3.1 hpi; p > 0.28); t4 (36.3 ± 3.4 vs. 36.9 ± 3.7 hpi; p > 0.20); t5 (47.9 ± 4.7 vs. 48.0 ± 4.8 hpi; p > 0.88); t8 (54.0 ± 6.5 vs. 54.1 ± 6.5 hpi; p > 0.91); tSB (86.3 ± 14.6 vs 85.7 ± 15.5 hpi; p > 0.78) and tB (93.0 ± 16.9 vs. 93.2 ± 17.2 hpi; p > 0.94). These findings suggest that the timing of key developmental events does not vary between male and female ICSI-derived preimplantation embryos. Limitations, reasons for caution The main limitation of this study is its retrospective nature and sample size. We analyzed the data of embryos leading to a live birth; therefore, caution is warranted when generalizing results to non-implanting embryos. Wider implications of the findings Male and female human embryos display similar morphokinetic patterns throughout preimplantation development in our study. Accordingly, embryo selection in a timelapse setting based on developmental characteristics does not bias sex ratios in resulting live births. Trial registration number not applicable

Metabolic Signature of Energy Metabolism Alterations and Excess Nitric Oxide Production in Culture Media Correlate with Low Human Embryo Quality and Unsuccessful Pregnancy.

Notwithstanding the great improvement of ART, the overall rate of successful pregnancies from implanted human embryos is definitely low. The current routine embryo quality assessment is performed only through morphological criteria, which has poor predictive capacity since only a minor percentage of those in the highest class give rise to successful pregnancy. Previous studies highlighted the potentiality of the analysis of metabolites in human embryo culture media, useful for the selection of embryos for implantation. In the present study, we analyzed in blind 66 human embryo culture media at 5 days after in vitro fertilization with the aim of quantifying compounds released by cell metabolism that were not present as normal constituents of the human embryo growth media, including purines, pyrimidines, nitrite, and nitrate. Only some purines were detectable (hypoxanthine and uric acid) in the majority of samples, while nitrite and nitrate were always detectable. When matching biochemical results with morphological evaluation, it was found that low grade embryos (n = 12) had significantly higher levels of all the compounds of interest. Moreover, when matching biochemical results according to successful (n = 17) or unsuccessful (n = 25) pregnancy, it was found that human embryos from the latter group released higher concentrations of hypoxanthine, uric acid, nitrite, and nitrate in the culture media. Additionally, those embryos that developed into successful pregnancies were all associated with the birth of healthy newborns. These results, although carried out on a relatively low number of samples, indicate that the analysis of the aforementioned compounds in the culture media of human embryos is a potentially useful tool for the selection of embryos for implantation, possibly leading to an increase in the overall rate of ART.

P–213 Comparative optical analysis of spindle reformation after oocyte vitrification with media containing differing basal formulations

Abstract Study question Do the base ingredients and total composition of vitrification media have an effect on meiotic spindle reformation in warmed donor oocytes? Summary answer Meiotic spindle reformation occurs more readily in donor oocytes vitrified and warmed with a contemporary culture media based vitrification formulation than in traditional vitrification media. What is known already Embryo culture trends continue towards more freeze-all cycles and oocyte preservation is becoming more prevalent across all age groups, thus vitrification continues to serve a pivotal role in today’s laboratory; however, the formulation of vitrification media remains largely unchanged from the m199 or mHTF base composition of antiquated slow freeze media. Literature identifies temperature as a key determiner in spindle reformation. Our preliminary data utilizing a robust vitrification medium with a basal formulation specifically designed for human embryo growth demonstrates a pronounced positive effect on oocytes post-warm in regard to spindle recovery time. Study design, size, duration In a prospective study, 30 oocytes obtained from a diverse population of 10 oocyte donors donating to an egg bank were imaged prior to vitrification to identify the meiotic spindle using the Oosight Imaging System (Hamilton Thorne). Donor oocytes were then split between two vitrification media groups, Vitrification Kit NX (FujiFilm Irvine Scientific) and Vitrification Media (Kitazato USA). After warming, oocytes were again imaged at various time points and meiotic spindle retardance was noted. Participants/materials, setting, methods Oocytes from approved egg bank donors were imaged, vitrified and warmed using protocols recommended by the manufacturers. The oocyte donors were all cycled and retrieved in the same private IVF Clinic and Laboratory between October 2019 and February 2020. Temperature of media, culture dishes, incubators and work stations were all monitored and maintained. Retrieved oocytes were imaged prior to vitrification. Oocytes were imaged immediately upon warm, and at 1 and 3 hours post warm. Main results and the role of chance Oocyte survival was similar across the two media groups, with Vitrification Kit NX at 86.7% and Vitrification Media at 80.0% survival. 100% of the degenerated oocytes in Vitrification Kit NX did not display an initial meiotic spindle when imaged prior to vitrification as opposed to 67% of the degenerate oocytes in Vitrification Media. Upon warming, immediate imaging showed oocytes from Vitrification Kit NX displayed a spindle at a rate of 41.7%, while Vitrification Media allowed this in 0% of the oocytes. At 1-hour post warm, Vitrification Kit NX and Vitrification Media displayed meiotic spindles in 83.3% and 22.2% of oocytes, respectively. The final time point was imaged at 3-hours post warm and showed meiotic spindle reformation in 91.7% of Vitrification Kit NX oocytes and 66.7% of Vitrification Media oocytes. While none of the time points imaged show significance, there is a defined trend towards a faster rate of meiotic spindle recovery in vitrification media formulated with a more modern culture media base. Limitations, reasons for caution The preliminary findings of this study offer that the composition and formulation of the vitrification medium perhaps do have an effect on the reformation of the meiotic spindle post-warm; however, more information is needed and a larger population size must be examined prior to discerning any significance. Wider implications of the findings: If, through further study and imaging, it is ascertained that meiotic spindle reformation is determined in part by the vitrification media composition, it could lead to potentially healthier warmed oocytes for the patient and less workload and scheduling stress on the embryologists due to shorter wait times prior to ICSI. Trial registration number Not applicable

Motherhood of women with uterine factor infertility

Abstract Aim. The aim of this paper is to present alternative ways for women with uterine factor infertility to achieve motherhood. Material and methods. Analysis of professional literature including the issues of surrogate motherhood, uterine transplantation and ectogenesis. Results. The infertility caused by uterine factor affects 3-5% of women in the world. There are also women who wish to conceive a baby out of their own genetic material, despite having a structurally abnormal uterus or lacking this organ altogether. Due to considerable advancements in reproductive medicine, the needs of such women can now be met via extracorporeal fertilisation and embryo implantation into the uterine cavity of another woman – surrogacy, or in special cases, via uterus transplantation. Another controversial concept is ectogenesis, i.e. technology which would allow for the growth of human embryos outside the mother’s body in an artificial uterus. The surrogate is considered when treatment and other reproduction methods have not worked well. This procedure is legal and accepted in some countries, while in others it is strongly opposed. Conclusions. There is growing demand for accurate and modern diagnostic and therapeutic methods allowing for successful reproduction. The proposed solutions may seem unreal, but the results of the research carried out to embody them seem to be promising.

The impact of selected embryo culture conditions on ART treatment cycle outcomes: a UK national study.

STUDY QUESTIONAre selected embryo culture conditions namely media, oxygen level, and incubator type, associated with IVF live birth rate (LBR) and the health of singleton offspring at birth?SUMMARY ANSWERThere were statistically significant differences in LBR between the eight culture media systems analysed; however, none of the embryo culture factors showed statistically significant associations with birth weight (BW) in multivariable regression analyses.WHAT IS KNOWN ALREADYIn clinical ART culture media is the initial environment provided for the growth of human embryos. Pre-implantation development is a critical period of developmental plasticity, which could have long-lasting effects on offspring growth and health. Although some studies have shown an impact of culture medium type on BW, the interaction between culture medium type and associated culture conditions on both treatment success rates (LBR) and offspring BW is largely unexplored. This study aimed to examine these factors in a large multicentre national survey capturing the range of clinical practice.STUDY DESIGN, SIZE, DURATIONIn this cross-sectional study, data from a survey circulated to all UK IVF clinics requesting information regarding culture medium type, incubator type, and oxygen level used in ART between January 2011 and December 2013 were merged with routinely recorded treatment and outcome data held in the Human Fertilisation and Embryology Authority Register up to the end of 2014.PARTICIPANTS/MATERIALS, SETTING, METHODSForty-six (62%) UK clinics responded to the survey. A total of 75 287 fresh IVF/ICSI cycles were captured, including 18 693 singleton live births. IVF success (live birth, singleton or multiple; LB), singleton gestation and singleton gestation-adjusted BW were analysed using logistic and linear regression models adjusting for patient/treatment characteristics and clinic-specific effects.MAIN RESULTS AND THE ROLE OF CHANCECulture medium type was shown to have some impact on LBR (multivariable logistic regression, (MRL); post-regression Wald test, P < 0.001), but not on BW (MLR; post-regression Wald test, P = 0.215). However, blastocyst culture had the largest observed effect on odds of LBR (odds ratio (OR) = 1.35, CI: 1.29–1.42), increased the risk of pre-term birth even when controlling for oxygen tension (MLR; OR = 1.42, CI: 1.23–1.63), and gestation-adjusted BW (MLR, β = 38.97 g, CI: 19.42–58.53 g) when compared to cleavage-stage embryo culture. We noted a very strong effect of clinic site on both LBR and BW, thus confounding between treatment practices and clinic site may have masked the effect of culture conditions.LIMITATIONS, REASONS FOR CAUTIONLarger datasets with more inter-centre variation are also needed, with key embryo culture variables comprehensively recorded in national treatment registries.WIDER IMPLICATIONS OF THE FINDINGSThis study is the largest investigation of laboratory environmental effects in IVF on both LBR and singleton BW. Our findings largely agree with the literature, which has failed to show a consistent advantage of one culture media type over another. However, we noted some association of LBR with medium type, and the duration of embryo exposure to laboratory conditions (blastocyst culture) was associated with both LBR and singleton health at birth. Because of the strong effect of clinic site noted, further randomized controlled trials are needed in order to reliably determine the effect of embryo culture on IVF success rates and the growth and health of subsequent offspring.STUDY FUNDING/COMPETING INTEREST(S)This study was funded by the EU FP7 project grant EpiHealthNet (FP7-PEOPLE-2012-ITN -317 146). The authors have no competing interests to declare.

Elusive master organizer of human embryo growth seen for the first time

Elusive master organizer of human embryo growth seen for the first time

Does human embryo growth rate affect the outcome of vitrified-warmed blastocyst transfer?

Does human embryo growth rate affect the outcome of vitrified-warmed blastocyst transfer?

Electrochemical lactate biosensor based upon chitosan/carbon nanotubes modified screen-printed graphite electrodes for the determination of lactate in embryonic cell cultures

l-lactate is an essential metabolite present in embryonic cell culture. Changes of this important metabolite during the growth of human embryo reflect the quality and viability of the embryo. In this study, we report a sensitive, stable, and easily manufactured electrochemical biosensor for the detection of lactate within embryonic cell cultures media. Screen-printed disposable electrodes are used as electrochemical sensing platforms for the miniaturization of the lactate biosensor. Chitosan/multi walled carbon nanotubes composite have been employed for the enzymatic immobilization of the lactate oxidase enzyme.This novel electrochemical lactate biosensor analytical efficacy is explored towards the sensing of lactate in model (buffer) solutions and is found to exhibit a linear response towards lactate over the concentration range of 30.4 and 243.9µM in phosphate buffer solution, with a corresponding limit of detection (based on 3-sigma) of 22.6µM and exhibits a sensitivity of 3417±131µAM−1 according to the reproducibility study. These novel electrochemical lactate biosensors exhibit a high reproducibility, with a relative standard deviation of less than 3.8% and an enzymatic response over 82% after 5 months stored at 4°C. Furthermore, high performance liquid chromatography technique has been utilized to independently validate the electrochemical lactate biosensor for the determination of lactate in a commercial embryonic cell culture medium providing excellent agreement between the two analytical protocols.

Growth retardation in human blastocysts increases the incidence of abnormal spindles and decreases implantation potential after vitrification

Does the human embryo growth rate affect the outcome of vitrified-warmed blastocyst transfer? Following vitrification, the incidence of abnormal spindle morphology was increased and the implantation competence was decreased in growth-retarded embryos compared with normally developing embryos. Various types of spindle abnormality occur in human cleavage- and blastocyst-stage embryos. However, the incidence of abnormal spindle morphology in growth-retarded blastocysts is not known. Furthermore, there is conflicting data about the implantation potential of such blastocysts. This was a retrospective cohort study including 878 single vitrified-warmed blastocyst transfers between 9 January 2010 and 10 July 2012, and an experimental study using 121 vitrified-warmed blastocysts donated to research. A comparison on the implantation potential and spindle shape of vitrified-warmed blastocysts was made between normally developing and growth-retarded blastocysts. In the clinical study, we compared the implantation rates of vitrified-warmed embryos that developed to the blastocyst stage on Day 5 after insemination (normally developing embryos) with those that required culture to Day 6 (growth-retarded embryo). In the experimental study, donated vitrified-warmed blastocysts were immunostained with an anti-α-tubulin antibody to visualize microtubules, an anti-γ-tubulin antibody to image centrosomes and Hoechst 33342 or 4,6-diamidino-2-phenylindole to visualize DNA. Confocal image analysis captured a z-series stack of 0.5-µm-thick optical sections encompassing the entire blastocyst. Only spindles with fusiform poles and with chromosomes aligned at the equator were classified as normal. The implantation rate of growth-retarded embryos (47%, n = 270) was significantly lower (P < 0.05) than that of normally developing embryos (57%, n = 608). A total of 533 spindles were analyzed in Day 5 and 6 vitrified-warmed blastocysts. The incidence of abnormal spindles in the growth-retarded embryos (47%, n = 274) was significantly higher (P < 0.01) than in the normally developing embryos (30%, n = 259). Further studies are required to clarify the link between an increase in abnormal spindle formation and a decrease in embryonic implantation potential. This study provided new insights into the possible implications of abnormalities in spindle formation in growth-retarded human blastocysts.

Glycoprotein 130 promotes human blastocyst development in vitro

To investigate the efficacy of leukemia inhibitory factor (LIF) and/or glycoprotein 130 (gp130) on in vitro growth of human embryos. Laboratory study. University hospital-based IVF clinic. A total of 164 frozen embryos that survived thawing were cultured in media supplemented with LIF and/or gp130 or control media. Morphological development was evaluated by light microscopy. Protein expression profiles of single blastocysts were evaluated using matrix-assisted laser desorption/ionization time of flight-based intact cell mass spectrometry. Embryo development and protein content. Addition of gp130 to culture media improved blastocyst formation (73% vs. 43%). Addition of LIF to the culture media did not improve embryo development. Protein fingerprint spectra were obtained that revealed significant intensity changes for multiple molecular species including thymosin beta-10, thymosin beta-4, histone H2A, histone H2B, histone H4, ubiquitin, ubiquitin-T, and acyl-CoA binding protein. Glycoprotein 130, but not LIF, seems to be beneficial for preimplantation embryo development, implicating a physiological role in regulating preimplantation development in humans and thus ought to be included in culture media designed for embryo culture to the blastocyst stage. Furthermore, these findings highlight the great potential of matrix-assisted laser desorption/ionization time of flight mass spectrometry and intact cell mass spectrometry as a versatile tool in reproductive medicine research.

Oxygen Regulates Amino Acid Turnover and Carbohydrate Uptake During the Preimplantation Period of Mouse Embryo Development1

Oxygen is a powerful regulator of preimplantation embryo development, affecting gene expression, the proteome, and energy metabolism. Even a transient exposure to atmospheric oxygen can have a negative impact on embryo development, which is greatest prior to compaction, and subsequent postcompaction culture at low oxygen cannot alleviate this damage. In spite of this evidence, the majority of human in vitro fertilization is still performed at atmospheric oxygen. One of the physiological parameters shown to be affected by the relative oxygen concentration, carbohydrate metabolism, is linked to the ability of the mammalian embryo to develop in culture and remain viable after transfer. The aim of this study was, therefore, to determine the effect of oxygen concentration on the ability of mouse embryos to utilize both amino acids and carbohydrates both before and after compaction. Metabolomic and fluorometric analysis of embryo culture media revealed that when embryos were exposed to atmospheric oxygen during the cleavage stages, they exhibited significantly greater amino acid utilization and pyruvate uptake than when cultured under 5% oxygen. In contrast, postcompaction embryos cultured in atmospheric oxygen showed significantly lower mean amino acid utilization and glucose uptake. These metabolic changes correlated with developmental compromise because embryos grown in atmospheric oxygen at all stages showed significantly lower blastocyst formation and proliferation. These findings confirm the need to consider both embryo development and metabolism in establishing optimal human embryo growth conditions and prognostic markers of viability, and further highlight the impact of oxygen on such vital parameters.

The effect of infertility and assisted reproduction on first-trimester placental and fetal development

Our investigation of differences in first-trimester placentation and/or fetal biometry in pregnancies conceived spontaneously compared with those conceived through fertility treatment, and comparing less invasive fertility treatment with in vitro fertilization found no statistically significant difference in first-trimester abnormal placentation or fetal growth between pregnancies conceived spontaneously and those conceived through fertility treatment, or between the in vivo and in vitro subgroups.

Human implantation: the last barrier in assisted reproduction technologies?

Implantation processes are highly complex involving the actions of numerous hormones, immunoglobulins, cytokines and other factors in the endometrium. They are also essential matters for the success of assisted reproduction. The nature of early embryonic development is of equal significance. It involves ovarian follicle growth, ovulation, fertilization and preimplantation growth. These processes are affected by imbalanced chromosomal constitutions or slow developmental periods. Post-implantation death is also a significant factor in cases of placental insufficiency or recurrent abortion. Clearly, many of these matters can significantly affect birth rates. This review is concerned primarily with the oocyte, the early embryo and its chromosomal anomalies, and the nature of factors involved in implantation. These are clearly among the most important features in determining successful embryonic and fetal growth. Successive sections cover the endocrine stimulation of follicle growth in mice and humans, growth of human embryos in vitro, their apposition and attachment to the uterus, factors involved in embryo attachment to uterine epithelium and later stages of implantation, and understanding the gene control of polarities and other aspects of preimplantation embryo differentiation. New aspects of knowledge include the use of human oocyte maturation in vitro as an approach to simpler forms of IVF, and new concepts in developmental genetics.

Gonadotropin-releasing hormone agonist to induce final oocyte maturation prevents the development of ovarian hyperstimulation syndrome in high-risk patients and leads to improved clinical outcomes compared with coasting

Ninety-four women undergoing IVF with peak E2 level>4000 pg/mL received leuprolide acetate (LA) trigger (LA trigger group) or had gonadotropins withheld for one or more days (coasting group) followed by hCG trigger, unless cycle cancellation occurred. There were no cases of ovarian hyperstimulation syndrome in either group, and the LA trigger group had significantly more oocytes retrieved (26.9+/-9.5 vs. 17.7+/-9.3) P<0.001, more normally fertilized oocytes (15.0+/-7.8 vs. 10.3+/-6.3) P=0.01, and higher clinical and ongoing pregnancy rates than the coasting group (52.5% vs. 27.2%; 49.2% vs. 24.2%, P=0.02 for both comparisons, respectively).

Role of total antioxidant capacity in the differential growth of human embryos in vitro

The objective of this study was to examine the relationship of early human embryonic development parameters with day 1 culture media total antioxidant levels (day 1 TAC). Prospective study. Patients undergoing assisted reproduction (ART) in a teaching hospital. Patients undergoing conventional IVF (n = 153; 167 cycles) and intracytoplasmic sperm injection (ICSI; n = 105; 116 cycles) were included. Both fertilization and early cultures were performed in human tubal fluid (HTF) with 5% serum substitute supplement. Levels of total antioxidants in the central well (sample) and the outer well (control) of each embryo culture dish were measured. Fertilization rate and embryo quality at days 3 and 5 were recorded for each cycle. Age, parity, and demographic features were also compared. After controlling for all demographic and clinical variables, day 1 TAC was related to fertilization rates in both groups of patients. Day 1 TAC was significantly related to high (>7) day 3 cell number, low (<10%) fragmentation rate, and blastocyst development rate in both conventional IVF and ICSI cycles. Day 1 TAC was related to pregnancy in ICSI but not conventional IVF cycles. Day1 TAC appears to be an important biochemical marker for early embryonic growth. Decreased embryonic fragmentation, enhanced cleavage rate, and increased blastocyst development rate may be partially related to day 1 TAC in the culture media. Whether this relationship is a cause or effect needs further assessment.

Differential growth of human embryos in vitro: Role of total antioxidant capacity

Pregnancy rates in assisted reproductive technologies are sub-optimal despite substantial technical improvements in the last decade. Better understanding of in vitro embryonic growth is of extreme importance as little is known about the biological, biochemical, and metabolic functions of pre-implantation embryos. Recently, the presence of various oxidative/antioxidant systems in a number of reproductive tissues has sparked an interest in studying the relationship of oxidative stress parameters with different aspects of reproduction.

Differential growth of human embryos in vitro: Role of reactive oxygen species

To examine the relationship of early human embryonic development with the level of reactive oxygen species (ROS) in the culture media on the first day (day 1 ROS) after insemination. A prospective study. Patients undergoing assisted reproduction in a teaching hospital. Patients undergoing conventional IVF (n = 104; 115 cycles) and intracytoplasmic sperm injection (ICSI) (n = 91; 96 cycles) were included. Both fertilization and early cultures were performed in human tubal fluid with 5% serum substitute supplement. Day 1 ROS levels in the central well (sample) and the outer well (control) of each embryo culture dish were measured after overnight incubation by chemiluminescence assay using luminol as the probe. Fertilization rate and embryo quality at day 3 and 5 were recorded for each cycle. Age, parity, and demographic features were also compared. High day 1 ROS levels in culture media were associated with low blastocyst rate, low fertilization rate, low cleavage rate, and high embryonic fragmentation with ICSI but not with conventional IVF. High day 1 ROS levels in culture media were associated with lower pregnancy rates in both IVF and ICSI cycles. Reactive oxygen species generated in culture media by day 1 may be an important biochemical marker for early embryonic growth. Increased embryonic fragmentation and slow cleavage rate may be partially attributed to early exposure of embryos to high ROS levels in ICSI cycles. Differential growth of ICSI embryos incubated under identical conditions may be in part due to differences in ROS levels of the culture medium surrounding these embryos.

A randomized controlled study comparing human embryo growth in sequential blastocyst media with or without Vero cell coculture.

A randomized controlled study comparing human embryo growth in sequential blastocyst media with or without Vero cell coculture.

Micromanipulation of human gametes and embryos: ooplasmic donation at fertilization VIDEO.

It is well known that human embryos may from anomalies both in vitro and in vivo. Progress through the preimplantation stages can be marked by multiple nuclei in some or all blastomeres, the formation of numerous fragments of varying size and organized in different patterns, and by arrests in development at virtually any stage. Various parameters have been offered as markers of the success of embryo growth and its culmination in implantation. Some of these involve characteristics in the follicles such as size, steroid output, properties of cumulus cells and others. Most involve studies on embryos in vitro, analysing timing of cleavage, blastomere structure, chromosome complement and timing of blastulation. More recently, characteristics in the structure of the pronuclei or of the ooplasm have been introduced. Certain dysmorphisms in the oocyte may predict implantation failure (Van Blerkom et al., 1995), whereas other characteristics hint at polarity in the pronucleate egg to make a detailed forecast of the likelihood of particular embryos achieving implantation (Scott and Smith, 1998). Cytogenetic studies using fluorescence in-situ hybridization of all cells from whole embryos have shown that certain morphological markers such as pronuclear and blastomere size can predict anomalies with high accuracy (S.Munne and J.Cohen, manuscript submitted). Such studies may ultimately help embryologists to assist in selecting embryos for replacement of cryopreservation. Virtually all of these issues remain to be proven in large-scale prospective controlled trials, yet there is much optimism that some of these parameters will be applied, and some of them demand no more than examining the eggs in vitro. Another approach to improving the growth of human embryos is to interfere physically or embryologically with them in order to avert an impending problem or to set them on the correct pathway to full-term development. In a sense, changing culture medium is one form of manipulation. More relevant to the present video, intrusive methods such as assisted hatching, zona removal, excising cytoplasmic fragments, and ooplasmic donation (Cohen et al.,

Female and male human embryo growth rates are similar before the eight-cell stage

OBJECTIVE: Our purpose was to assess the possible relationship between human embryo growth rates and sexual differentiation. STUDY DESIGN: We analyzed 142 conceptional in vitro fertilization and embryo transfer cycles undertaken in 137 women (151 embryos transferred) in which each embryo transferred led to a gestational sac. Embryos were sorted into three groups according to the number of blastomeres assessed just before embryo transfer: ≤3, 4, and ≥5 blastomeres. RESULTS: Percentages of girls and boys remained roughly unaltered irrespective of the number of blastomeres observed just before embryo transfer: ≤3 blastomeres, 45% and 55%; 4 blastomeres, 44% and 56%; and ≥5 blastomeres, 45% and 55%, respectively (statistical power 90% at the 5% significance level). CONCLUSIONS:This indicates that embryo growth rates before the eight-cell stage are not related to the sex of the live-born infant, thereby dissuading the use of embryo growth rates in the appraisal of sex likelihood in regular in vitro fertilization–embryo transfer. (Am J Obstet Gynecol 1998;178:45-9.)