Culture of human spare preembryos: association between blastocyst formation and pregnancy

The Relationship between Number of Supernumerary Blastocysts Cryopreserved and Probability of a Live Birth Outcome after Single Fresh Blastocyst Transfer: Analysis of over 10 Thousand Cycles

The ability to predict the likelihood of a live birth after single fresh embryo transfer is an important part of fertility treatment. While past studies have examined the likelihood of live birth based on the number of oocytes retrieved and cleavage-stage embryos available, the odds of a live birth based on the number of supernumerary blastocysts cryopreserved following a fresh embryo transfer has not been rigorously studied. We performed a retrospective analysis, stratified by age, on patients undergoing their first fresh autologous single day 5 blastocyst transfer to assess relationship between the likelihood of a live birth and number of supernumerary blastocysts cryopreserved. In patients aged <35 years and 35-39 years old, the likelihood of a live birth increased linearly between 1 and 6 supplementary blastocysts and non-linearly if 10 or more blastocysts were cryopreserved. When aged 40 years and above, the likelihood of a live birth increased linearly up to 4 cryopreserved blastocysts and then non-linearly if 10 or more blastocysts were cryopreserved. The present study demonstrated a non-linear relationship between the number of supernumerary blastocysts cryopreserved and the likelihood of a live birth after single blastocyst transfer in the first autologous fresh IVF/ICSI cycle across different age groups.

Development speed of sibling embryo positively reflects live birth rate after fresh day 3 embryo transfer

The ability of sibling embryos to form blastocysts may reflect the developmental potential of the embryos that were transferred into the uterus. The purpose of the study was to investigate whether the development speed of sibling embryos positively reflects the live birth rate following fresh embryo transfer. We examined 1262 cycles of women who underwent day 3 (D3) cleavage embryo transfer in the Peking Union Medical College Hospital in 2015-2020, who were divided into three groups (D5, D5 + D6, and D6) according to blastocyst formation. The live birth rate in patients with blastocysts that formed on D6 was significantly lower than the other two groups (36.1%, 45.6% and 44.7%, P < 0.05). For women with blastocysts that formed on D6, the live birth rate was higher in those with more good quality blastocysts than poor-quality blastocysts (42.4 vs 32.3%, P < 0.05). Multiple regression analysis showed that the blastocyst development speed of sibling embryos was an independent factor affecting live birth after fresh embryo transfer (P < 0.05). We concluded that the blastocyst development speed of sibling embryos may reflect live birth rate following the transfer of D3 cleavage embryos.

Number of supernumerary vitrified blastocysts is positively correlated with implantation and live birth in single-blastocyst embryo transfers

OBJECTIVE

To estimate whether live birth in single-blastocyst transfers is correlated with the number of sibling supernumerary vitrified blastocysts (embryos not transferred) generated from that same cycle.

DESIGN

Retrospective cohort study.

SETTING

A large academic assisted reproduction clinic.

PATIENT(S)

All single-blastocyst transfers in 2010 graded as "good" embryos by Society for Assisted Reproductive Technologies (SART) criteria.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Implantation and live birth.

RESULT(S)

Of the 655 single-blastocyst transfers that met inclusion criteria, implantation occurred in 65% and live birth in 54% of cycles. In chi-square analysis, patients with supernumerary vitrified blastocysts had a statistically higher implantation rate (65% versus 50%) and live-birth rate (56% versus 41%) when compared with patients without supernumerary blastocysts. Univariate logistic regression demonstrated an increase in implantation (OR 1.09; 95% CI, 1.03-1.15) and live birth (OR 1.06; 95% CI, 1.02-1.09) with increasing number of supernumerary blastocysts. Multivariate logistic regression analysis demonstrated that patient age and the number of supernumerary blastocysts were statistically significantly associated with implantation and live birth.

CONCLUSION(S)

The number of supernumerary vitrified blastocysts correlated positively with the odds of implantation and live birth in good quality single-blastocyst transfers. Patients with supernumerary blastocysts are good candidates for single-embryo transfer.

Oviductal cells and early conception

The ability to bypass the oviduct by fertilizing human oocytes in vitro and then transferring the ensuing embryos into the uterine environment to produce pregnancies that can be carried to term (assisted reproductive technology, ART) has made the real functional significance of the fallopian tube come under debate. The question has been raised as to whether the oviduct is a simple conduit, providing for the transport of gametes and embryos, or whether it has any functional relevance to early conception. In the field of ART, some reports claim that transfer of embryos either to the uterus or to the oviduct yield similar results, while a greater amount of evidence confirms that tubal transfers are associated with higher pregnancy and take home baby rates, suggesting that unknown factors in the oviduct favour fertilization and embryo viability. This review attempts to provide some answers to questions about the role of oviductal cells in vivo during early conception and in vitro in the field of ART.

Cycle outcome can be predicted by the growth profile of untransferred cleavage-stage embryos

Excess embryos obtained from intracytoplasmic sperm injection cycles may be cultured and observed until day 5 if the couple receiving treatment do not want them to be cryopreserved. In order to investigate the correlation between blastocyst formation in extended culture and pregnancy outcome, 194 patients treated in two separate IVF units were examined retrospectively. The patients were separated into two groups: group 1 with at least one blastocyst formed in culture, and group 2 with no blastocyst formation. The pregnancy rates were 60.0% and 41.7% for groups 1 and 2, respectively. The pregnancy rate in group 1 was statistically significantly higher than in group 2 (P = 0.01). The results suggest that the developmental potential of embryos obtained from a single assisted reproduction treatment cycle may be similar and that blastocyst formation in vitro may help to predict the pregnancy outcome of that cycle.

Advanced embryo development during extended in vitro culture: observations of formation and hatching patterns in non-transferred human blastocysts

Human embryos not chosen for fresh transfer or cryopreservation were maintained in extended in vitro culture for up to 9 days after fertilization to observe blastocyst formation and hatching features. These non-transferred embryos were derived from 64 consecutive IVF cycles, and were not cryopreserved either because of compromised morphology or because the patients did not consent to cryopreservation for personal reasons. Embryos were cultured individually to monitor daily growth until developmental arrest, and differential blastocyst formation and hatching were analysed among groups of patients and embryos. In the population studied, hatching occurred most commonly on day 7 after fertilization (range 5-9 days). A total of 301 blastocysts was observed, of which 116 (38.5%) eventually hatched in vitro irrespective of day of formation. A trend towards earlier blastocyst formation and a greater likelihood of hatching was noted in this population. Both blastocyst formation and hatching appeared negatively correlated with increasing maternal age and higher basal serum FSH concentrations on day 3 of development, although these trends did not reach statistical significance. Comparison of intracytoplasmic sperm injection (ICSI) (n = 25) and conventional insemination (n = 39) cycles showed a similar rate of blastocyst formation in both groups (54 and 52%, respectively; P > 0.05), but hatching patterns varied significantly between these groups (4.1 versus 61.6%, respectively; P < 0.0001). The discovery of marked impairment of hatching among non-transferred ICSI embryos supports the case for reconsideration of the appropriateness of assisted blastocyst hatching in selected cases.

Blastocyst culture and transfer: a step toward improved in vitro fertilization outcome

OBJECTIVE

To evaluate the efficacy of blastocyst culture and transfer in human in vitro fertilization (IVF) as compared to day 3 embryo transfer.

DESIGN

Prospective randomized trial.

SETTING

Private assisted reproduction unit.

PATIENT(S)

A total of 162 IVF patients were included in the day 3 embryo transfer (n = 82) and blastocyst transfer (n = 80) groups.

INTERVENTION(S)

Embryo transfer on day 3 after culture in the standard culture media and blastocyst transfer on day 5 or 6 after culture in the sequential culture media.

MAIN OUTCOME MEASURE(S)

Implantation and pregnancy rates, multiple gestation rate.

RESULT(S)

The implantation rate for embryos transferred at the blastocyst stage was significantly higher than that for embryos transferred on day 3 (26% vs. 13%). The viable pregnancy rate was similar in both groups (29% vs. 26%). Significantly fewer embryos were required for transfer at the blastocyst stage compared with day 3 embryo transfer (2.0 +/- 0.1 vs. 3.5 +/- 0.63). The high-order multiple gestation rate was significantly less with the blastocyst transfer than with the day 3 embryo transfer (4% vs. 19%).

CONCLUSION(S)

With the use of blastocyst culture, a few embryos can be transferred without decreasing the overall pregnancy rate. This may reduce multiple gestations and improve human IVF outcome.

Comparison of blastocyst transfer with day 3 embryo transfer in similar patient populations

OBJECTIVE

To compare implantation and pregnancy rates (PRs) achieved with blastocyst transfer (BT) and day 3 ET in similar patient populations.

DESIGN

Retrospective analysis.

SETTING

Academic infertility center.

PATIENT(S)

One hundred consecutive patients <40 years undergoing IVF, each with more than three eight-cell embryos on day 3.

INTERVENTION(S)

Patients used their own eggs for IVF or IVF and intracytoplasmic sperm injection. Embryos were cultured in P1 medium (Irvine Scientific, Santa Ana, CA) until day 3, when they were either transferred or, in the case of embryos for BT, incubated in Blastocyst Medium (Irvine Scientific), followed by transferring on day 5.

MAIN OUTCOME MEASURE(S)

Implantation and PRs.

RESULT(S)

There were no statistically significant differences in patient age, FSH level, or number of oocytes or zygotes. The BT group had fewer embryos transferred (mean, 2.4) compared with the day 3-ET group (mean, 4.6). The viable PR (cardiac activity at 6-7 weeks was considered indicative of a viable pregnancy) was higher with BT (68%, 34/50) than with day 3 ET (46%, 23/50). The implantation rate was increased with BT (47%, 56 sacs/120 embryos) compared with day 3 ET (20%, 46 sacs/231 embryos).

CONCLUSION(S)

The BT group in our study had higher implantation and PRs compared with the day 3-ET group. Better embryo selection, improved embryo-uterine synchrony, and decreased cervical mucus on day 5 may have accounted for the enhanced outcome. Our data support the use of BT to limit the number of embryos transferred while improving PRs.

Sibling embryo blastocyst development correlates with the in vitro fertilization day 3 embryo transfer pregnancy rate in patients under age 40

OBJECTIVE

To examine the IVF day 3-ET pregnancy rate in patients under 40 with sibling embryo blastocyst development, compared with similar patients without blastocyst formation.

DESIGN

Retrospective analysis.

SETTING

Academic infertility center.

PATIENT(S)

One hundred twenty-five IVF day 3-ET patients under 40 with sibling embryos for extended culture.

INTERVENTION(S)

Extended culture of nontransferred sibling embryos for blastocyst development.

MAIN OUTCOME MEASURE(S)

Pregnancy and multiple gestation rates, number of oocytes, embryos formed, and embryos transferred.

RESULT(S)

Thirty-eight percent of patients became pregnant. Forty-eight percent of patients had sibling embryos develop to blastocyst. The blastocyst group had more oocytes retrieved (17.4+/-6.6 versus 14.4+/-5.6), more embryos formed (11.2+/-4.2 versus 8.8+/-3.2), and a higher clinical pregnancy rate (60% versus 18%) than the group without blastocyst development.

CONCLUSION(S)

Blastocyst transfer has been shown to improve implantation rates and reduce the risk of multiple gestations from assisted reproductive technology. Sibling embryo blastocyst development may reflect superior embryo quality, as manifested by increased IVF-ET pregnancy rates. In addition to predicting pregnancy in the current cycle, sibling embryo blastocyst development may provide information about the potential for fresh blastocyst transfer in subsequent cycles and help to identify patients at risk for multiple gestations.

Use of coculture with cumulus cells in insemination medium in human in vitro fertilization (IVF)

PURPOSE

In an initial trial, 16 of 33 (48%) bipronuclear human zygotes left in culture in the insemination drop from which they had originated developed to fully expanded blastocysts.

RESULTS

This method was subsequently used for all supernumerary embryos judged unsuitable for replacement or cryopreservation on Day 1, 2, or 3 of development. Over a 4-year period, embryos reaching the fully expanded blastocyst stage were cryopreserved. Of 113 such blastocysts thawed, 81 survived (72%), and upon transfer to 52 patients, 8 clinical pregnancies were established (15%), of which 6 were live births. Subsequently, following modification of some culture parameters, 60 patients had 296 supernumerary embryos cultured for 6 days; 43 of these patients (72%) had 148 embryos (50%) that cavitated and 134 (45%) of these cavitating embryos were judged to be fully expanded blastocycts; 125 (42%) of these embryos were cryopreserved.

CONCLUSION

The blastocyst formation rate is similar to that reported by others using conventional culture procedures or coculture on Vero or other cell types. I conclude that cumulus cells are a ready source of feeder cells for the coculture of human embryos.