Initial experience with extended culture and blastocyst transfer of cryopreserved embryos

The optimal frozen embryo transfer strategy for the recurrent implantation failure patient without blastocyst freezing: thawing day 3 embryos and culturing to day 5 blastocysts

This study aimed to investigate the optimal frozen embryo transfer (FET) strategy for recurrent implantation failure (RIF) patients with three consecutive failed cleaved embryo implantations and no blastocyst preservation. This retrospective analysis was divided into three groups based on the FET strategy: thawed day 3 embryo transfer (D3 FET group); and extended culture of frozen-thawed day 3 embryos to day 5 blastocysts transfer (D3-D5 FET group); thawed blastocyst transfer (D5 FET group). Transplant cycle data were compared between the three groups. In total, 43.8% of vitrified-thawed cleavage embryos developed into blastocysts. Analysis of the three transplantation strategies showed that, compared with the D3 FET group, D3-D5 had a significantly better hCG-positivity rate and live-birth rate (P < 0.05). Pregnancy outcomes in the D3-D5 FET group and D5 FET group were similar regarding hCG-positivity rate, implantation rate, clinical pregnancy rate, and live-birth rate. Our findings propose two potentially valuable transfer strategies for patients experiencing repeated implantation failures. The D3-D5 FET approach presents a greater potential for selecting promising embryos in cases without blastocyst preservation; however, this strategy does entail the risk of cycle cancellation. Conversely, in instances where blastocyst preservation is an option, prioritizing consideration of the D5 FET strategy is recommended.

Development of properly-polarized trophoblast stem cell-derived organoids to model early human pregnancy

The development of human trophoblast stem cells (hTSC) and stem cell-derived trophoblast organoids has enabled investigation of placental physiology and disease and early maternal-fetal interactions during a stage of human pregnancy that previously had been severely restricted. A key shortcoming in existing trophoblast organoid methodologies is the non-physiologic position of the syncytiotrophoblast (STB) within the inner portion of the organoid, which neither recapitulates placental villous morphology in vivo nor allows for facile modeling of STB exposure to the endometrium or the contents of the intervillous space. Here we have successfully established properly-polarized human trophoblast stem cell (hTSC)-sourced organoids with STB forming on the surface of the organoid. These organoids can also be induced to give rise to the extravillous trophoblast (EVT) lineage with HLA-G + migratory cells that invade into an extracellular matrix-based hydrogel. Compared to previous hTSC organoid methods, organoids created by this method more closely mimic the architecture of the developing human placenta and provide a novel platform to study normal and abnormal human placental development and to model exposures to pharmaceuticals, pathogens and environmental insults.

Motivation

Human placental organoids have been generated to mimic physiological cell-cell interactions. However, those published models derived from human trophoblast stem cells (hTSCs) or placental villi display a non-physiologic "inside-out" morphology. In vivo , the placental villi have an outer layer of syncytialized cells that are in direct contact with maternal blood, acting as a conduit for gas and nutrient exchange, and an inner layer of progenitor, single cytotrophoblast cells that fuse to create the syncytiotrophoblast layer. Existing "inside-out" models put the cytotrophoblast cells in contact with culture media and substrate, making physiologic interactions between syncytiotrophoblast and other cells/tissues and normal and pathogenic exposures coming from maternal blood difficult to model. The goal of this study was to develop an hTSC-derived 3-D human trophoblast organoid model that positions the syncytiotrophoblast layer on the outside of the multicellular organoid.

Graphical abstract

Cryopreservation of human embryos at the morula stage and outcomes after transfer

OBJECTIVE

To evaluate the survival rate of human morula embryo freezing and the morphological alterations during freezing, during and after thawing, and their applications in embryo selection.

DESIGN

Retrospective observational study.

SETTING

Private infertility clinic.

PATIENT(S)

Consecutive patients under age 39 undergoing frozen morula embryo transfers from December 1999 to May 2003.

INTERVENTION(S)

Embryo freezing was performed at the morula stage. Embryo thaw and post-thaw ETs were conducted on the same day, which is equivalent to a day 4 ET.

MAIN OUTCOME MEASURE(S)

Morphological alterations during freezing and thawing and after thawing. Post-thaw embryo survival rates, transferable rates, pregnancy rates, and implantation rates.

RESULT(S)

Morula embryos showed reversed morphological alterations during the freezing process; these alterations were recovered during thawing or shortly after the thawing. Post-thaw survival rates showed no significant difference between any of the morula substages. However, embryos scored as grade 3, which represented good quality, had significantly higher post-thaw survival and transferable rates than grade 2 and 1 embryos. Patients who received at least one grade 3 embryo had significantly higher pregnancy rates, implantation rates, and ongoing/live birth rates than other groups.

CONCLUSION(S)

An acceptable survival rate can be achieved after cryopreservation of human morula embryos, and morphological alterations that occur during and shortly after an embryo thaw can be a feasible index for determining viable embryos.

Quantitative grading of a human blastocyst: optimal inner cell mass size and shape

OBJECTIVE

To investigate the predictive value of quantitative measurements of blastocyst morphology on subsequent implantation rates after transfer.

DESIGN

Prospective observational study.

SETTING

Private assisted reproductive technology center.

PATIENT(S)

One hundred seventy-four IVF patients receiving transfers of expanded blastocyst-stage embryos on day 5 (n = 112) or day 6 (n = 62) after oocyte retrieval.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Blastocyst diameter, number of trophectoderm cells, inner cell mass (ICM) size, ICM shape, and implantation and pregnancy rates.

RESULT(S)

Blastocyst diameter and trophectoderm cell numbers were unrelated to implantation rates. Day 5 expanded blastocysts with ICMs of >4,500 microm(2) implanted at a higher rate than did those with smaller ICMs (55% vs. 31%). Day 5 expanded blastocysts with slightly oval ICMs implanted at a higher rate (58%) compared with those with either rounder ICMs (7%) or more elongated ICMs (33%). Implantation rates were highest (71%) for embryos with both optimal ICM size and shape. Pregnancy rates were higher for day 5 transfers of optimally shaped ICMs compared with day 5 transfers of optimally sized ICMs.

CONCLUSION(S)

Quantitative measurements of the inner cell mass are highly indicative of blastocyst implantation potential. Blastocysts with relatively large and/or slightly oval ICMs are more likely to implant than other blastocysts.

Dramatic declines in implantation and pregnancy rates in patients who undergo repeated cycles of in vitro fertilization with blastocyst transfer after one or more failed attempts

OBJECTIVE

To compare the outcome of second and third cycles of in vitro fertilization with blastocyst transfer to the outcome of first attempts at IVF with blastocyst transfer.

DESIGN

Retrospective study.

SETTING

Private ART center.

PATIENT(S)

Three hundred and four patients undergoing treatment with in vitro fertilization with blastocyst transfer, 87 of which underwent at least one cycle of re-treatment after failing to achieve pregnancy in their first cycle.

INTERVENTION(S)

Bipronucleate oocytes were grown for up to 144 hours and subsequently transferred when at least one embryo attained the expanded blastocyst stage.

MAIN OUTCOME MEASURE(S)

Pregnancy and implantation rates.

RESULT(S)

Pregnancy rates per retrieval were significantly higher for patients undergoing their first cycle of in vitro fertilization with blastocyst transfer (36%) compared to those undergoing their second (19%) or their third (9%) cycles of treatment. Implantation rates per embryo were also higher for first cycles of in vitro fertilization with blastocyst transfer (30%) compared to second (18%) or third cycles (8%).

CONCLUSION(S)

Pregnancy and implantation rates decline dramatically in repeated cycles of in vitro fertilization with blastocyst transfer following one or more unsuccessful cycles of in vitro fertilization with blastocyst transfer.

A comparison of day 5 and day 6 blastocyst transfers

OBJECTIVE

To compare implantation and pregnancy rates according to the day of embryo transfer (day 5 or 6 after oocyte retrieval) when transfer was postponed until expanded blastocysts developed.

DESIGN

Retrospective clinical study.

SETTING

Private ART center.

PATIENT(S)

One-hundred and eighty-three women undergoing blastocyst-stage embryo transfer following in vitro fertilization.

INTERVENTION(S)

Bipronucleate oocytes were grown for up to 144 hours and subsequently transferred only when at least one embryo attained the expanded blastocyst stage.

MAIN OUTCOME MEASURE(S)

Implantation and pregnancy rates.

RESULT(S)

Blastocysts transferred on day 5 implanted at nearly twice the rate of blastocysts transferred on day 6 (36.3% vs. 19.0%). Pregnancy rates were also almost twice as high among the day 5 transfer patients (59.3% vs. 32.3%). In addition, more blastocysts developed (3.6 vs. 2.4), and more were transferred (2.7 vs. 2.3) to the day 5 transfer patients, although the proportion of expanded blastocysts among the blastocysts that were transferred was the same for the two groups (91.7% vs. 93.6%).

CONCLUSION(S)

Embryos that develop to the expanded blastocyst stage and are transferred on day 5 after retrieval are approximately twice as likely to implant compared to those for which expansion and transfer are delayed until day 6.

Blastocyst transfer: does it really affect the outcome?

Blastocyst transfer is of great interest to most assisted reproductive technology clinics. The ability to select the best embryos to transfer in order to increase pregnancy rates, and to replace lower numbers of embryos to reduce the likelihood of an unwanted multiple pregnancy have both been realized. The optimal method to prolong embryo culture up to day 5 or 6 is still to be identified, although present techniques offer acceptable blastocyst development rates. Freezing of supernumerary blastocysts is still a matter of discussion, as adequate results are still awaited.