Freezing of preembryos: early vs late stages

Patient- and cycle-specific factors affecting the outcome of frozen-thawed embryo transfers

PURPOSE

This study attempted at identifying the main parameters influencing the outcome of frozen embryo transfers.

METHODS

This is a single-center retrospective cohort study of 830 frozen-embryo-transfer cycles performed at a German university hospital from January 2012 to December 2016. Main outcome parameters were the clinical pregnancy and live birth rate. Twelve patient- and cycle-dependent factors were analyzed in terms of their influence on the outcome of frozen embryo transfers. Multivariate logistic regression analysis was used for the modelling of the dependency of the different parameters on outcomes.

RESULTS

The clinical pregnancy rate in our study was 25.5%, the live birth rate was 16.1% with an average maternal age of 34.2 years at the time of the oocyte retrieval. In the univariate analysis age, number of transferred embryos, blastocyst versus cleavage stage transfer, embryo quality and mode of endometrial preparation affected the birth rate significantly. The birth rate after artificial endometrial preparation was significantly lower than the birth rate after transfers in modified natural cycles (12.8 versus 20.6% with p = 0.031). The multivariate logistic regression analysis showed a significant independent influence of age, number of transferred embryos, culture duration and mode of endometrial preparation on the frozen embryo transfer success rates. Body mass index, nicotine abuse, a history of PCO syndrome or endometriosis and the co-transfer of a second poor-quality embryo to a good-quality embryo appeared to be irrelevant for the outcome in our collective.

CONCLUSION

Age, number of transferred embryos, embryo culture duration and the mode of endometrial preparation are independent predictive factors of frozen embryo transfer outcomes.

Impact of serum estradiol levels on the implantation rate of cleavage stage cryopreserved-thawed embryos transferred in programmed cycles with exogenous hormonal replacement

PURPOSE

To investigate the impact of late follicular phase serum estradiol (E2) levels on implantation and pregnancy outcomes of cleavage stage cryopreserved/thawed embryos transferred in programmed cycles with exogenous hormonal replacement.

METHODS

Retrospective cohort analysis of IVF patients with transfer of cryopreserved-thawed day-3 embryos in E2 and progesterone (P4) supplemented cycles (n = 208 cycles).

MAIN OUTCOME MEASURES

implantation and pregnancy rates according to late follicular phase serum E2 levels and early secretory phase E2/P4 ratios.

RESULTS

Logistic regression performed for embryo implantation and for pregnancy outcome in relation to E2 (day 15), P4 (day 15 and 16), before (crude analysis) and after adjustment (adjusted analysis) for baseline characteristics (including age, BMI, serum basal cycle day 3 FSH levels, embryo quality, endometrial lining thickness) showed no significant association. Similarly, ROC analysis showed no impact of cycle day 16 E2/P4 ratio.

CONCLUSIONS

Neither late follicular phase serum E2 nor the early E2/P4 ratio were able to predict implantation or pregnancy outcome of day-3 cryopreserved-thawed embryos transferred in artificially programmed cycles.

Comparing thaw survival, implantation and live birth rates from cryopreserved zygotes, embryos and blastocysts

CONTEXT:

Most in vitro fertilization (IVF) programs employ embryo cryopreservation to enhance pregnancies from a single ovarian stimulation. More embryos are created, some of which are not transferred to the uterus immediately, generating a need for improved cryopreservation protocols. One protocol may involve growing embryos to a further stage of development, allowing only embryos with proven developmental capabilities to be cryopreserved. Here we examined thaw survival, implantation and live birth rates of embryos cryopreserved at different stages.

AIMS:

We examined thaw survival, implantation and live birth rates of embryos cryopreserved at the zygote, day 3 (D3) embryos or blastocyst stage.

SETTINGS AND DESIGN:

This is a retrospective study from a single academic IVF program.

PATIENTS AND METHODS:

A retrospective study of all patients who had frozen embryos transferred to their uteri from year 2002 to 2008 at a single academic IVF program was conducted.

STATISTICAL ANALYSIS USED:

Analysis of variance followed by Fisher's Exact Test was performed to compare the survival after thaw, implantation and live birth rates between the three groups.

RESULTS:

One thousand nine hundred and ninety-one zygotes, 2880 D3 embryos and 503 blastocysts were frozen using a slow freeze technique, thawed and transferred. Significantly more D3 embryos and blastocysts survived the thawing process compared to zygotes and significantly higher implantation rate per number of thawed blastocysts was achieved than that for zygotes. Live birth rates were similar between the three groups.

CONCLUSIONS:

Growing embryos to blastocyst stage prior to cryopreservation is associated with fewer frozen embryos but does not appear compromise patients’ chance of achieving pregnancy

Cryopreserved embryos in the United States and their availability for research

OBJECTIVE

To determine the number of embryos stored at assisted reproductive technology (ART) clinics in the United States and their current disposition.

DESIGN

A targeted survey instrument sent by the SART-RAND team to all medical practices providing in vitro fertilization services in the United States.

RESULTS

The SART-RAND team surveyed all 430 ART practices in the United States. Of these practices, 340 returned surveys for analysis. The data from these surveys were merged with data taken from the 1999 SART dataset, which contains information about practice size and success rates. Responding clinics reported a total of 396,526 embryos in storage as of April 11, 2002. The vast majority of the embryos (88.2%) were targeted for patient use. Small numbers of embryos were available for research, donation, destruction, quality assurance, or other uses.

CONCLUSIONS

Nearly 400,000 embryos are stored in the United States, the majority of which (88.2%) are targeted for patient use. Few are available for research (2.8%), limiting possible conversion into embryonic stem cell lines.

Pronuclear stage cryopreservation after intracytoplasmic sperm injection and conventional IVF: implications for timing of the freeze

OBJECTIVE

To compare clinical outcomes of frozen embryo transfers using cryopreserved pronuclear stage oocytes that had undergone either intracytoplasmic sperm injection (ICSI) or conventional IVF.

DESIGN

Observational.

SETTING

A tertiary referral reproductive medicine unit.

PATIENT(S)

Couples undergoing either ICSI or conventional IVF from January 1, 1995 to December 31, 1997.

INTERVENTION(S)

Patients underwent a standard controlled ovarian hyperstimulation protocol and transvaginal ultrasound-guided oocyte retrieval. All normally fertilized (2PN) oocytes exceeding a specified embryo number designated for fresh transfer were immediately cryopreserved at the pronuclear stage. Our cryopreservation method included timing of the freeze according to pronuclear morphology. Subsequent frozen embryo thaw-transfer cycles were usually performed by thawing only the intended number of embryos for transfer.

MAIN OUTCOME MEASURE(S)

Thaw survival rate, implantation rate, clinical pregnancy rate, delivery rate.

RESULT(S)

Ninety-six thaw-transfer cycles (n = 72) and 93 thaw-transfer cycles (n = 67) were undertaken in patients who had previously undergone conventional IVF or ICSI, respectively. Embryo thaw survival rates (IVF, 90.4%; ICSI, 91.1%) were similar. Clinical pregnancy (IVF, 40.6%; ICSI, 44.1%) and delivery (IVF, 36.4%; ICSI, 39.8%) rates per transfer, as well as implantation (IVF, 19.1%; ICSI, 19.9%) rates, were also similar. There were only four clinical pregnancy losses in both groups.

CONCLUSION(S)

Embryo thaw survival is similar for cryopreserved pronuclear stage oocytes derived from ICSI and conventional IVF. Clinical pregnancy, implantation and delivery rates were also similar for the two groups. In addition, there was no increase in the rate of pregnancy loss in ICSI patients after frozen embryo transfers.

Effect of Vero cell coculture on the development of frozen-thawed two-cell mouse embryos

PURPOSE

Our purpose was to evaluate the beneficial effects of long-term coculture of Vero cells on the development of frozen-thawed two-cell mouse embryos.

METHODS

Two-cell mouse embryos were frozen slowly with 1,2-propandiol and sucrose as cryoprotectants and thawed rapidly, followed by stepwise dilution. Vero cells were cultured in drops of RPMI 1640 to establish monolayers. Frozen-thawed embryos were cultured alone (control) or cocultured with Vero cells. The rate of development in both groups was compared.

RESULTS

After 4 days of culture, significantly more embryos in coculture were developed to expanded blastocysts (61 vs 37% for controls; P < or = 0.0001). In addition, on the fifth day of cultivation, more embryos in coculture showed the potential of hatching from the zona pellucida (26 vs 7% in controls; P < or = 0.0001). The rate of degeneration in coculture was also much lower than in controls (6 and 15%, respectively).

CONCLUSIONS

Coculture of cryopreserved preimplantation-stage embryos with Vero cells seems to be a useful tool to eliminate the postthaw deleterious effect of freezing and also to obtain better-quality embryos appropriate for transfer.