Influence of embryo transfer on blastocyst viability

Embryo location in the uterus during embryo transfer: An in vitro simulation

OBJECTIVE

To evaluate the location of transferred embryos under various parameters during embryo transfer in in vitro fertilization (IVF) by applying an in vitro experimental model for embryo transfer (ET).

METHODS

Mock ET simulations were conducted with a laboratory model of the uterine cavity. The transfer catheter was loaded with a sequence of air and liquid volumes, including development-arrested embryos donated by patients. The transfer procedure was recorded using a digital video camera. An orthogonal design, including three independent variables (uterine orientation, distance of the catheter tip to the fundus, and injection speed) and one dependent variable (final embryo position), was applied.

RESULTS

The uterine cavity was divided into six regions. The distribution of the transferred matter within the uterine cavity varied according to the uterine orientation. Medium speed-injected embryos were mostly found in the static region while fast- and slow-speed injected embryos were mostly found in the fundal region and the cervical-left region, respectively. The possibility of embryo separation from the air bubble increased from 11.1% in slow injection cases to 29.6% and 48.1% in medium and fast injection cases, respectively.

CONCLUSION

The experimental model provides a new method for investigating ET procedures. Fast injection of embryos into a retroverted uterus may be more likely to result in embryo separation from the air bubble.

The Influence Of Intrauterine Pressure On Embryo Retention In A Catheter After Embryo Transfer

The retention of the embryo in the transfer catheter after embryo transfer (ET) during in vitro fertilization is a very common phenomenon, encountered by even the most experienced operators, and embryos retained in the transfer catheter or its sleeve require a repeat transfer. The exact mechanism of embryo retention has not been explained. Therefore, the present study aimed to investigate the mechanism of embryo retention in the catheter during embryo transfer by using a transparent uterus model equipped with pressure sensors and a video recorder. The results indicate that pressure changes in the uterine cavity during ET can influence the distribution of the transferred fluid containing the embryo. Under certain conditions, the transferred fluid can flow backward in the catheter, which may lead to retention of the embryo in the catheter.

Estimation of embryo transfer media viscosity and consideration of its effect on media and uterine fluid interactions

RESEARCH QUESTION

What are the viscosities of media used for human embryo transfer and what is the possible effect of viscosity as it relates to interactions between transfer media and uterine fluid.

DESIGN

Chamber slide filling times, in seconds, were used to calculate viscosity for each commercial and in-house modified medium, with 12 or 24 replicates per medium under standard operating procedure temperature and gas equilibration conditions used for embryo transfer. Means, standard deviations and coefficients of variation were calculated, and each viscosity was estimated using a regression equation; viscosities for each medium were presented for comparative purposes.

RESULTS

Complete culture media (G1-Plus, G2-Plus, G-TL, 1-Step, Global Total, Global Total HEPES, and Sperm Wash Medium) had viscosity estimates of 1.65 cP, 1.77 cP, 1.68 cP, 1.29cP, 1.18 cP, 1.15 cP, and 1.20 cP, respectively. Complete transfer media (EmbryoGlue, UTM), had viscosity estimates of 3.59 cP and 1.28 cP, respectively. Global HEPES medium with 10%, 20%, 30%, and 50% synthetic serum substitute (SSS) volume per volume had viscosity estimates 1.16 cP, 1.23 cP, 1.25 cP, and 1.34 cP, respectively. For reference, water had a viscosity estimate of 1.06 cP.

CONCLUSIONS

A relatively narrow distribution of viscosities was observed across several transfer media despite the various commercial or in-house modifications. These data demonstrate the vast difference between viscosities of embryo transfer media and the assumed viscosity of uterine fluid (1000 cP). Contemporary embryo transfer media may be well-suited for IVF, but evaluation of all variables, e.g. media viscosity in the context of embryo transfer, adds to the knowledge base that should be available to practitioners.

Numerical simulation of embryo transfer: how the viscosity of transferred medium affects the transport of embryos

Background

Embryo transfer (ET) is a key step of assisted reproductive procedures, where the transferred medium containing the embryos is injected into the uterine cavity through a transcervical catheter and blended with intrauterine fluid in the uterine cavity. This procedure determines the delivery sites of embryos in the uterine cavity and has crucial impact on the implantation. Due to practical restrictions and ethical issues, it is often difficult to perform an in vivo study in humans to examine factors that affect the motions and delivery of embryos during ET. Alternatively, mathematical modeling is a powerful tool to that end.

Results

A computational model is developed to simulate the intrauterine mixing flow and track the embryo motions. Two important factors affecting the intrauterine flow are studied via this model: the viscosity of the transferred medium and the injection speed. Numerical results show that the dispersion pattern and the final delivery sites of the embryos are significantly influenced by the viscosity of the transferred medium. Specially, increasing the transferred medium viscosity close to that of the uterine fluid can enhance the probability that the embryos are delivered close to the fundus and keep them from being dragged backward to the cervix during catheter withdrawal. In addition, a slow injection speed can lower the driving force on the embryo during ET, which can prevent the embryo from being injured.

Conclusions

Based on our study, the practice of using a transferred medium with similar viscosity to that of the uterine fluid and a slow injection speed is recommended for real embryo transfer procedures in clinic.

Improving the safety of the embryo and the patient during in vitro fertilization procedures

In vitro fertilization (IVF) is a method of treatment for infertility in selected indications. Recent years have brought dynamic development of technologies related to IVF. This article presents problems pertaining to the safety of technology with respect to the patient, as well as the embryo, based on an analysis of scientific reports and our own experience. Invasiveness of the IVF procedure for the woman and the embryo varies on an individual basis. Minimization of the invasiveness of IVF requires experience of the staff performing the procedure, especially with respect to the assessment of risk for an individual patient. Technologies related to IVF are constantly being improved, and the effectiveness of the selected individual treatment methods is not always scientifically confirmed.

The cumulative effect of assisted reproduction procedures on placental development and epigenetic perturbations in a mouse model

Assisted reproductive technologies (ART) are associated with several complications including low birth weight, abnormal placentation and increased risk for rare imprinting disorders. Indeed, experimental studies demonstrate ART procedures independent of existing infertility induce epigenetic perturbations in the embryo and extraembryonic tissues. To test the hypothesis that these epigenetic perturbations persist and result in adverse outcomes at term, we assessed placental morphology and methylation profiles in E18.5 mouse concepti generated by in vitro fertilization (IVF) in two different genetic backgrounds. We also examined embryo transfer (ET) and superovulation procedures to ascertain if they contribute to developmental and epigenetic effects. Increased placental weight and reduced fetal-to-placental weight ratio were observed in all ART groups when compared with naturally conceived controls, demonstrating that non-surgical embryo transfer alone can impact placental development. Furthermore, superovulation further induced overgrowth of the placental junctional zone. Embryo transfer and superovulation defects were limited to these morphological changes, as we did not observe any differences in epigenetic profiles. IVF placentae, however, displayed hypomethylation of imprinting control regions of select imprinted genes and a global reduction in DNA methylation levels. Although we did not detect significant differences in DNA methylation in fetal brain or liver samples, rare IVF concepti displayed very low methylation and abnormal gene expression from the normally repressed allele. Our findings suggest that individual ART procedures cumulatively increase placental morphological abnormalities and epigenetic perturbations, potentially causing adverse neonatal and long-term health outcomes in offspring.

Tauroursodeoxycholic acid improves the implantation and live-birth rates of mouse embryos

We previously demonstrated that tauroursodeoxycholic acid (TUDCA) improved the developmental competence of mouse embryos by attenuating endoplasmic reticulum (ER) stress-induced apoptosis during preimplantation development. Here, we present a follow-up study examining whether TUDCA enhances the implantation and live-birth rate of mouse embryos. Mouse 2-cell embryos were collected by oviduct flushing and cultured in the presence or absence of 50 μM TUDCA. After culture (52 h), blastocysts were transferred to 2.5-day pseudopregnant foster mothers. It was found that the rates of pregnancy and implantation as well as the number of live pups per surrogate mouse were significantly higher in the TUDCA-treated group compared to the control group, but there was no significant difference in the mean weights of the pups or placentae. Thus, we report for the first time that TUDCA supplementation of the embryo culture medium increased the implantation and livebirth rates of transferred mouse embryos.

Influence of embryo transfer on embryo preimplantation development

OBJECTIVE

To investigate the impact of injection speeds of the transferred load on embryo development.

DESIGN

A laboratory model for in vitro simulation of ET was developed to investigate the impact of varying injection speeds of the transferred load on embryo development.

SETTING

Academic research institutes of reproduction biotechnology and private centers of reproductive medicine.

ANIMAL(S)

Mouse hybrid F(1) females (C57bl/10 J × CBA-H; N = 15) aged 2-3 months.

INTERVENTION(S)

In vitro exposure of mouse embryos with either the fast ET (ejection speed, >1 m/s) or slow ET (ejection speed, <0.1 m/s) and consecutive culture for 36 hours.

MAIN OUTCOME MEASURE(S)

Development rate, morphology and apoptotic index of embryos.

RESULT(S)

The development rate was the slowest in embryos exposed to the fast ET. Morphological changes in response to ET were observed only among embryos exposed to the fast ET. The mean apoptotic index was 17.6% in the group exposed to the fast ET, 5.6% in the group exposed to the slow ET, and 2.58% in the control group.

CONCLUSION(S)

A reduction of the ejection speed of the transferred load allows avoidance of a developmental delay and diminishes injury of the embryos. Therefore, it is reasonable to suggest transferring the embryos at the lowest possible ejection speed.

Pressure induced nucleus DNA fragmentation

PURPOSE

The present study was designed to investigate the impact of pressure on nuclear DNA integrity in viable cells of mouse blastocysts.

METHODS

The blastocysts of hybrid F1 females [(C57Bl/10 J × CBA-H);N = 15] aged 2-3 months were exposed into the pressure impulse lasting ~0.021 s and characterized by a positive pressure peak of ~76 mmHg. The nuclear DNA fragmentation index of mouse blastocysts was assessed by TUNEL assay within 60 s after exposure to pressure impulse.

RESULTS

The mean nuclear DNA fragmentation index was significantly higher in the experimental group (83%) than in the control group (19.7%); p < 0.001.

CONCLUSION(S)

A low magnitude pressure impulse can induce nuclear DNA fragmentation in mouse blastocysts. The compression and decompression forces appearing during pressure fluctuations are responsible for the observed DNA shearing.