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PubMed1990

Construction of aggregation chimaeras from 8-cell mouse embryos stored for several years in liquid nitrogen.

Eight-cell embryos of 7 different inbred strains frozen and stored for 2 to 4 years in liquid nitrogen were used as the source of embryos and individual 1/8-blastomeres for construction of different types of aggregation chimaeras. Overall survival of stored embryos, evaluated by in vitro culture, ranged from 63% in A/By to 85% in C57BL/10By embryos. Chimaeric embryos prepared by aggregation of frozen/thawed zona-free 8-cell embryos continued in normal development through expanding blastocysts (77% to 93%) to in vitro implantations. Construction of directed chimaeras by total rebuilding of 8-cell embryos previously stored in liquid nitrogen was successful and resulted in normal development. Of the aggregates made by regular mixing of 1/8-blastomeres obtained from BALB/c and C57BL/6J embryos thawed from liquid nitrogen, 90% reached the blastocyst stage and 77% implanted after 48 h and 96 h of in vitro culture, respectively. Addition of 1/8 blastomeres from frozen/thawed BALB/c embryos to four 1/8-like blastomeres from nuclear transplantation experiments documented, as all of the 30 constructed aggregates formed expanding blastocysts within 48 h of in vitro culture, the possibility of using embryos from embryo banks for the rescue of products of genetic manipulations at the embryo level.

Animals↗
PubMed1995

Effect of genotype on the efficiency of mouse embryo cryopreservation by vitrification or slow freezing methods.

We examined possible genotype effects on the survival of 8- to 16-cell mouse embryos isolated from four inbred strains (C57BL/6N, BALB/cAnN, DBA/2N, and C3H/HeN), a outbred stock (ICR), and various crosses after cryopreservation by vitrification or conventional slow freezing using glycerol solutions. The rates of in vitro development of C57BL/6N, BALB/cAnN, C3H/HeN, and ICR embryos to expanded blastocysts ranged from 86% to 94% after slow freezing and 85% to 97% after vitrification. The cryopreservation method did not significantly influence in vitro embryo survival after thawing (P > 0.05). Although genotype significantly influenced the in vitro survival of embryos (P = 0.008), this presumably resulted from an increased difficulty in assessing the quality grade of C3H/HeN embryos prior to cryopreservation. The rates in vivo development of C57BL/6N, BALB/cAnN, C3H/HeN, DBA/2N, and ICR embryos to normal day 18-19 fetuses ranged from 19% to 64% after slow freezing and from 18% to 63% after vitrification. The in vivo development of cryopreserved embryos was significantly influenced by cryopreservation method and genotype (P = 0.01 and P = 0.001, respectively). Vitrification yielded significantly higher rates of in vivo development than that after slow freezing (P > 0.05). In vivo development rates of DBA/2N and ICR female X B6D2F1 male embryos after cryopreservation were significantly higher than that of embryos from BALB/cAnN and C3H/HeN mice (P < 0.05). These results indicate that parental genotype exerts little or no effect on the ability of embryos to develop in vitro after vitrification or slow freezing. Differences in the ability of cryopreserved embryos to develop normally in vivo may reflect inherent genotype related differences in their post-implantation developmental potential and not their sensitivity to cryoinjury.

Animals↗
PubMed1994

Characterization and prediction of IVF cycles generating "slow-cleaving" embryos.

PURPOSE: To characterize and predict cycles generating open quote slow-cleaving closed quote embryos in in vitro fertilization, 86 cycles were retrospectively divided into two groups (open quote slow, closed quote n=41, and open quote fast, closed quote n=45) according to whether the number of blastomeres per embryo on day 3 was < or = or > than the mean of the distribution, respectively. RESULTS: Cycles generating open quote slow-cleaving closed quote embryos were treated with luteinizing hormone-releasing hormone agonist before ovarian stimulation for a shorter period (12.1 +/- 0.5 versus 15.6 +/- 1.1 days; P < or = 0.01) and had higher immaturity grade of oocyte-corona-cumulus complexes which resulted in embryos (1.6 +/- 0.1 vs 1.3 +/- 0.1; P < or = 0.05) when compared to cycles producing "fast-cleaving" embryos. Both variables entered in a logistic regression model applied in order to predict the probability of a cycle generating "slow-cleaving" embryos (goodness-of-fit chi-square = 180.0, degrees of freedom (df) = 80, P = 0.4786). This model predicted correctly 86.7% (13 of 15) of cycles generating "slow-cleaving" embryos and 83.3% (10 of 12) of cycles producing "fast-cleaving" embryos when the estimated probability of a cycle producing "slow-cleaving embryos" was > or = 0.7 or < or = 0.3, respectively. CONCLUSION: Shorter treatment with hormone-releasing hormone agonist before ovarian stimulation and higher immaturity grade of oocyte- corona-cumulus complexes which result in embryos are predictive characteristics of in vitro fertilization cycles generating "slow-cleaving" embryos.

Adult↗
PubMed2005

Effect of eCG dose and ovulation induction treatments on embryo recovery and in vitro development post-vitrification in two selected lines of rabbit does.

The aim of this work was to evaluate the effect of different doses of eCG administered subcutaneously (0, 50 and 200 IU) and the hormonal induction of ovulation (GnRH or hCG) on embryo recovery and in vitro development of embryos post-vitrification in two selected lines of rabbit does. The two selected lines were line V (selected for the litter size at weaning) and line R (selected for growth rate). Administration of 200 IU of eCG significantly increased ovulation rate (19.2 +/- 1.2 versus 15.5 +/- 1.1 and 12.2 +/- 1.3, and the number of haemorrhagic follicles (13.8+/-1.6 versus 3.8+ /- 1.4 and 3.8 +/- 1.7), but significantly decreased recovery rate (28.8 +/- 6.3 versus 47.7 +/- 5.7 and 48.7 +/- 6.7, 200 IU versus 50 IU and 0 IU eCG, respectively), the number of normal embryos recovered per doe with at least one embryo (5.8 +/- 0.9 versus 8.2 +/- 0.9, 200 IU versus 50 IU eCG doses) and the in vitro development of embryos post-vitrification (51.9% versus 66.1%, 200 IU versus 50 IU eCG doses, respectively). Inducing ovulation with hCG significantly increased ovulation rate when compared with GnRH (17.3 +/- 0.8 versus 13.8+/-1.4), but no significant differences in embryo recovery and embryo development post-vitrification were observed between the two treatments. No significant differences were observed between the two selected lines in ovulation and recovery rates, the number of haemorrhagic follicles and the number of recovered embryos per doe. However, the post-vitrification in vitro rate of development was 59.7% for line R and 51.9% for line V (p < 0.05). It was concluded that the use of 50 IU of eCG subcutaneous with hCG or GnRH prior to embryo cryopreservation programmes in rabbits achieves the best results for embryo recovery, with the best development of recovered embryos post-vitrification.

Animals↗
PubMed2006

Embryo culture medium: which is the best?

With the growing move in in-vitro fertilization (IVF) clinics to transfer fewer embryos to women, there is an increasing reliance on the IVF laboratory to maximize embryo viability. Subsequently, there is justified scrutiny on the culture system and the media used to sustain the human embryo in vitro. The transfer of fewer embryos to patients also creates an increased dependence on the ability to cryopreserve embryos successfully. Therefore, in addition to the ability of a culture system to produce a single top-quality embryo for transfer, it is also necessary to enhance the cryotolerance of sibling embryos so that they can survive freezing or vitrification. Therefore, when examining which culture media is the best, it is prudent to not only examine the ability of a culture system to produce a pregnancy with the one or two highest-grade embryos, but also to determine how many embryos from the entire cohort (both fresh and frozen embryos) are capable of producing a live birth. Additionally, research on animal models has demonstrated that stress, and the resultant adaptation to conditions during pre-implantation stages, can affect pregnancy loss and fetal growth. It is therefore important to understand the role of each medium component and to identify possible sources of cellular stress to the embryo that will ultimately affect the function and viability of the conceptus.

Blastocyst↗
PubMed2006

Factors that affect infertility patients' decisions about disposition of frozen embryos.

OBJECTIVE: To describe factors that affect infertility patients' decision making regarding their cryopreserved embryos. DESIGN: Forty-six semistructured in-depth interviews of individuals and couples participating in IVF programs. SETTING: Two major southeastern academic medical centers. PATIENT(S): Fifty-three individuals, including 31 women, 8 men, and 7 couples. MAIN OUTCOME MEASURE(S): Qualitative analysis of interview transcripts. INTERVENTION (S): None. RESULT(S): Seven broad themes informed participants' decisions about embryo disposition: family and personal issues, trust, definition of the embryo, prospective responsibility to the embryo, responsibility to society, adequacy of information, and lack of acceptable disposition options. Many wished for alternative options, such as a ceremony at the time of disposal or placement of embryos in the woman's body when pregnancy was unlikely. CONCLUSION(S): Recent debates regarding embryo disposition do not reflect the range of values that infertility patients consider when deciding about frozen embryos. In addition to questions about the embryo's moral status, decision making about embryos is informed by a range of factors in the lives of individuals who created them. These perspectives may have important implications for the content and timing of informed consent, facilitating embryo disposition, and advancing policy debates about the ethics of frozen embryo use.

Adult↗
PubMed2006

Improved vitrification method allowing direct transfer of goat embryos.

The aim of this study was to design a vitrification method suited to field embryo transfer experiments in goat. In a first experiment, a standard vitrification protocol, previously designed for sheep embryos was compared to slow freezing of goat embryos. No significant difference was observed on kidding rate (48% versus 69%, respectively), nor on embryo survival rate (35% versus 45%). Second experiment: all embryos were vitrified. After warming, embryos were either transferred directly (direct transfer), or after in vitro dilution of the cryoprotectants (conventional transfer). The kidding rate was not affected by the transfer method (38% versus 23%, respectively). However, embryo survival rate tended to be higher after direct transfer (26% versus 14%). Third experiment: OPS vitrification was compared to standard vitrification. The kidding rate was not affected (22% versus 39%, respectively), but the embryo survival rate was lower after OPS (14% versus 28%). Fourth experiment: 0.4M sucrose was added with cryoprotectants in vitrification. The kidding rate after direct transfer was significantly enhanced after addition of sucrose (56% versus 27%, respectively), whereas embryo survival rate was not significantly affected (32% versus 18%). Fifth experiment: vitrification with sucrose supplementation was compared to slow freezing. No significant difference was observed after direct transfer on kidding rate (52% versus 31%, respectively), but embryo survival rate tended to be higher after vitrification (34% versus 21%). In conclusion, our results indicate that addition of 0.4M sucrose in association with direct transfer improves significantly the viability of goat vitrified embryos.

Animals↗
PubMed2001

Birth of healthy twins from in vitro development of human refrozen embryos.

OBJECTIVE: To avoid the risk of ovarian hyperstimulation syndrome and promote pregnancy rate by freezing pronuclear embryos at the oocyte retrieval and using developed refrozen supernumerary embryos in the event of failed pregnancies. DESIGN: A case study. SETTING: Private IVF center. PATIENT(S): Healthy infertile woman undergoing IVF treatment. INTERVENTION(S): Slowly frozen and rapidly refrozen embryos at varying stages of embryonic development were transferred. MAIN OUTCOME MEASURE(S): Survival rate of refrozen and thawed embryos; safety of refrozen embryo transference. RESULT(S): Fertilized pronuclear embryos that were frozen, thawed, and developed to morula embryos were subsequently vitrified, rethawed, and cultured until blastocyst formation before transfer. Healthy fraternal twins were born by caesarian section. The result of transfer was the novel finding of a successful delivery after the use of refrozen embryos. CONCLUSION(S): The transfer of refrozen supernumerary embryos resulted in successful pregnancy and delivery. We will continue to investigate the safety and efficacy of the elective freezing of all embryos as well as their refreezing so that supernumerary embryos can be reused to avoid ovarian hyperstimulation syndrome or in cases of repeated failed pregnancies.

Cryopreservation↗
PubMed1996

The age-related decline in female fecundity: a quantitative controlled study of implanting capacity and survival of individual embryos after in vitro fertilization.

OBJECTIVE: To determine strictly comparable rates per embryo of implantation and birth of a baby related to the woman's age, which would be representative of natural fertility at least in relative terms. DESIGN: Comparative study of IVF-ET results controlling for confounding variables including cause and duration of infertility, history of previous pregnancy, hormonal treatment, rank cycle of treatment, and numbers of embryos transferred and available. SETTING: University comprehensive fertility service. PATIENTS: All couples (n = 561) in their first cycle of treatment reaching oocyte collection, women with normal uterus and ovulatory cycles, and men with normal sperm. INTERVENTIONS: Standardized methods of pituitary desensitization, ovarian stimulation, and IVF-ET, and maximum of three embryos transferred. MAIN OUTCOME MEASURES: Oocytes, pregnancies, and live births per cycle; fertilization and cleavage rates; embryo implantation and live baby rates. RESULTS: The numbers of oocytes and consequent embryos declined with age but fertilization and cleavage rates rose slightly. Embryo implantation rates were reduced when no more than three embryos were available (9.3 percent), especially in women aged 35 to 39 years (6.2 percent) or older compared with four or more embryos (17.1 percent) but were equally low in all women over 40 years even with more embryos (6.1 percent). In the age bands 25 to 29, 30 to 34, 35 to 39, and 40 to 44 years, the rates per embryo of implantation were 18.2 percent, 16.1 percent, 15.3 percent, and 6.1 percent, respectively, and of a live baby were 15.7 percent, 12.1 percent, 12.0 percent, and 3.5 percent. CONCLUSIONS: Embryo implanting ability and survival decline gradually after 30 years of age, but by more than two thirds after 40 years and in younger women with reduced ovarian capacity.

Adult↗
PubMed1997

Preimplantation genetic diagnosis increases the implantation rate in human in vitro fertilization by avoiding the transfer of chromosomally abnormal embryos.

OBJECTIVE: To verify the percentage of chromosomally abnormal preimplantation embryos in patients with a poor prognosis and possibly to increase the chance of implantation by selecting chromosomally normal embryos. DESIGN: A prospective, randomized, controlled study. SETTING: In vitro fertilization program at the Reproductive Medicine Unit of the Società Italiana Studi Medicina della Riproduzione, Bologna, Italy. PATIENT(S): In a total of 28 stimulated cycles, the maternal age was > or = 38 years and/or the patient had > or = 3 previous IVF failures, factors that indicated a poor prognosis. After consent, 11 patients underwent preimplantation genetic diagnosis for aneuploidy, whereas 17 controls underwent assisted zona hatching. INTERVENTION(S): Simultaneous analysis of chromosomes X, Y, 13, 18, and 21 in a blastomere biopsied from day-3 embryos. Chromosomal analysis was performed with fluorescence in situ hybridization. Assisted zona hatching was performed on day-3 embryos from the control-group patients. MAIN OUTCOME MEASURE(S): Embryo morphology, results of fluorescence in situ hybridization, clinical pregnancies, and implantation. RESULT(S): In the study group, a total of 61 embryos were analyzed by fluorescence in situ hybridization, and 55% were chromosomally abnormal. Embryo transfer with at least one normal embryo was performed in 10 cycles. Four clinical pregnancies resulted, with a 28.0% implantation rate. In the control group, 41 embryos were transferred in 17 cycles after the assisted zona hatching procedure, yielding four clinical pregnancies and an 11.9% implantation rate. CONCLUSION(S): Infertile patients classified as having a poor prognosis have a high percentage of chromosomally abnormal embryos. The advantage of selecting and transferring embryos with normal fluorescence in situ hybridization results has an immediate impact on implantation.

Adult↗
PubMed2003

Bovine herpesvirus-1 associated with single, trypsin-treated embryos was not infective for uterine tubal cells.

It has been reported that bovine herpesvirus-1 (BHV-1) remains associated with in vitro-produced (IVP) bovine embryos after exposure to the virus and either washing or trypsin treatment. However, it is not known if the quantity of virus associated with an exposed IVP embryo is likely to infect a recipient cow after transfer. The specific objective of this study was to determine if IVP embryos that were exposed to BHV-1 would infect uterine tubal cells (UTC) in a co-culture system. In vitro-produced Day 7 embryos were exposed to BHV-1 and then washed or trypsin treated according to the IETS guidelines. These embryos were then co-cultured individually or in groups with UTC in microdrops of tissue culture medium 199 (TCM 199) supplemented with 10% equine serum. Following co-culture for 48 h, virus isolation was attempted on the embryos and the UTC from each drop. Virus was detected in washed individual embryos, groups of washed embryos, groups of trypsin-treated embryos and the UTC co-cultured with each of these treatments. However, BHV-1 was not detected in the individual, trypsin-treated embryos or the UTC co-cultured with them. It is concluded that trypsin treatment might effectively prevent infection of recipients if individual, Day 7, exposed embryos were transferred into the uterus.

Animals↗
PubMed2006

Delivery of a healthy baby following the transfer of embryos cryopreserved for 13 years.

Although embryos can theoretically be frozen for an unlimited period of time, there is still uncertainty about how long embryos can be cryopreserved without compromising pregnancy outcome. Following transfer of fresh embryos obtained after IVF, surplus embryos are usually frozen for personal use in later treatments. A 40-year-old woman was admitted to the centre's embryo adoption programme. She had a 7-year-old son, was diagnosed with ovarian factor infertility and her husband had secretory azoospermia. They underwent two cycles of IVF with donor spermatozoa and one cycle of donor intrauterine insemination that ended in spontaneous abortion. At this point, the couple was admitted to the embryo adoption programme. Six frozen embryos, obtained from a couple that had had a pregnancy through IVF at the centre and that had abandoned their surplus frozen embryos, were assigned to this patient. All six embryos were cryopreserved for 13 years. Of these, three were transferred and the patient became pregnant and delivered a healthy boy. Thanks to the embryo adoption programme, these embryos, rather than being left frozen for an indefinite period of time, were transferred to a couple that was willing to adopt them, resulting in the birth of a healthy newborn.

Adult↗
PubMedDate not supplied

Day 3 versus day 5 embryo transfer: a prospective randomized study.

Transfer of embryos at the blastocyst stage has been associated with exceptionally high implantation rates. There are, however, only a few prospective randomized studies comparing day 3 versus day 5 embryo transfer. Furthermore, the number of embryos replaced in the day 3 group transfer is often higher than the number of blastocysts replaced, thereby affecting implantation rates. A total of 118 patients undergoing standard IVF/intracytoplasmic sperm injection who had developed at least three 8-cell embryos showing <20% extracellular fragmentation on day 3 were randomized for day 3 or day 5 transfer. A maximum of two embryos were replaced. In this prospective, randomized study the implantation and pregnancy potential of embryos transferred on day 3 or day 5 were compared. Equal numbers of embryos were replaced in the two groups. There was no statistically significant difference between day 3 and day 5 transfer regarding positive human chorionic gonadotrophin rates (70 versus 67%), clinical pregnancy rates (61 versus 51%), implantation rates (44 versus 37%), twinning rates (42 versus 41%) and rates of early pregnancy loss (15 versus 29%). Transfer of embryos on day 3 or 5 showed similar implantation rates when equal numbers of embryos were transferred. Embryo transfer at the blastocyst stage seems to have no advantage over day 3 transfer in patients with more than two 8-cell embryos showing less than 20% fragmentation on day 3.

Blastocyst↗
PubMed2002

Comparison of stereoscopy, light microscopy and ultrastructural methods for evaluation of bovine embryos.

The most important point in embryo transfer success is the evaluation of the stage of development and quality of embryos. Therefore, the purpose of this study was to compare the morphological evaluation of embryos using stereoscopy, light microscopy and electron microscopy in order to establish the accuracy of former method compared with more invasive and accurate procedures. For this purpose, 23 Brahman x Swiss cows were used and synchronized with Norgestomet 6 mg plus, 5 mg Estradiol valerate (Syncromate B(R), Rhone Merieux, Mexico, Mexico City) and superovulated with Folltropin-V 240 mg (Vetrepharm, Mexico, Mexico City). Non-surgical embryo collection was performed 7.5 days after insemination. Descriptive statistics analysis was used to assess the data. Seventy-eight embryos were collected and classified by stereoscopic microscopy, finding 51.2% (40) of good quality, 25.6% (20) fair and 24.3% (19) poor. Later, under light microscopy observation, evaluation of the same embryos resulted in 25.6% (20) good, 32.0% (25) fair and 42.3% poor quality. Finally, in the evaluation of embryos under electron microscopy 24.3% (19) were found to be of good quality, 29.3% (23) fair and 46.1% (36) poor. Evaluation of embryos with stereoscopic microscopy was found to be very subjective, as nearly 50% of embryos classified by this method as good quality, showed features of degenerative stages under light and electron microscopy. Embryos with these features are generally frozen and transferred, which could be one of the reasons for having low fertility rate in embryo transfer programmes.

Animals↗
PubMed1997

In-vitro development of refrozen mouse embryos.

To evaluate the effects of sequential, repetitive freezing on their in-vitro development, mouse embryos at the eight- to 16-cell stage were subjected to one of five treatments. They were (i) cultured as unfrozen controls, (ii) frozen once and cultured, (iii) subjected to two consecutive freeze-thaw cycles, (iv) frozen and thawed, and then cultured for 18-30 h before being frozen a second time, and (v) frozen three times in succession without being cultured. To assess their functional survival after freezing and thawing, all embryos were cultured in vitro to the hatched blastocyst stage in Whitten's medium. In one experiment, hatched embryos that developed after one, two or three cycles of freezing and thawing were stained with Hoechst 33342 to determine their mean cell number. More embryos of the culture control group and the once-frozen group developed into hatching blastocysts than those of the refrozen groups. There was no difference in the second post-thaw rate of in-vitro development for embryos refrozen with the culture-refreeze or direct-refreeze procedure. Furthermore, there was no difference among in-vitro development rates for embryos frozen two or three times. However, among those embryos subjected to repeated cycles of freezing and thawing that did not survive, there was a considerable amount of damage to their zonae pellucidae. Furthermore, frozen mouse embryos had fewer cells per embryo at the time of hatching than the unfrozen embryos. Nevertheless, these results demonstrate that mouse embryos can survive even three successive freeze-thaw cycles yet still be capable of in-vitro development.

Animals↗
PubMed1997

Prognostic factors for the success rate of embryo freezing.

To find some prognostic factors for the outcome of frozen-thawed cycles, we have retrospectively analysed all frozen pre-embryos that were thawed during 1993 and 1994 at two in-vitro fertilization (IVF) units in Sweden. Supernumerary pre-embryos were frozen from 551 oocyte retrievals and these resulted in 660 frozen-thawed cycles which lead to 623 thawed embryo transfers. The outcome of these transfers was 137 clinical pregnancies with a pregnancy rate of 22% per frozen-thawed embryo transfers. Women <40 years of age had a higher birth rate than those > or =40 years, 19 and 5% respectively (P < 0.01). Transfers with two and three pre-embryos resulted in pregnancy rates of 23 and 27%, respectively, compared with 14% for transfer of one embryo. A pregnancy resulting from the initial embryo transfers had a predictive value for results of the subsequent frozen-thawed cycle. Embryo grade and cleavage stage at the time of freezing was important for the survival of the frozen-thawed pre-embryos. The pregnancy rate was not influenced by the cleavage stage, but a tendency toward a lower pregnancy rate was seen for the embryos with lower grading. To conclude, cryopreservation seems to be beneficial in women <40 years of age, who have supernumerary pre-embryos of good quality for freezing and of which at least two can be transferred.

Adult↗
PubMed1999

Prevention of twin pregnancy after in-vitro fertilization or intracytoplasmic sperm injection based on strict embryo criteria: a prospective randomized clinical trial.

A prospective randomized study comparing single embryo transfer with double embryo transfer after in-vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) was carried out. First, top quality embryo characteristics were delineated by retrospectively analysing embryos resulting in ongoing twins after double embryo transfer. A top quality embryo was characterized by the presence of 4 or 5 blastomeres at day 2 and at least 7 blastomeres on day 3 after insemination, the absence of multinucleated blastomeres and <20% cellular fragments on day 2 and day 3 after fertilization. Using these criteria, a prospective study was conducted in women <34 years of age, who started their first IVF/ICSI cycle. Of 194 eligible patients, 110 agreed to participate of whom 53 produced at least two top quality embryos and were prospectively randomized. In all, 26 single embryo transfers resulted in 17 conceptions, 14 clinical and 10 ongoing pregnancies [implantation rate (IR) = 42.3%; ongoing pregnancy rate (OPR) = 38.5%] with one monozygotic twin; 27 double embryo transfers resulted in 20 ongoing conceptions with six (30%) twins (IR = 48.1%; OPR = 74%). We conclude that by using single embryo transfer and strict embryo criteria, an OPR similar to that in normal fertile couples can be achieved after IVF/ICSI, while limiting the dizygotic twin pregnancy rate to its natural incidence of <1% of all ongoing pregnancies.

Adult↗
PubMed1999

Impact of blastomere biopsy and cryopreservation techniques on human embryo viability.

The purpose of the present study was to evaluate the effect of cryopreservation on 55 embryos which had one blastomere biopsied for preimplantation genetic diagnosis of aneuploidy before freezing. The thawing outcome was compared to that obtained in 94 embryos which derived from our conventional freezing programme in patients with comparable characteristics who were treated in the same period. Their embryos were morphologically similar but the incidence of aneuploidy was 100% in the biopsy group and unknown in the controls. The percentage of embryos which survived intact after thawing was significantly lower in the biopsied group compared to the controls (9 versus 25% respectively; P < 0.025), whereas the rate of lysis was superior among biopsied embryos (34 versus 13% in the controls; P < 0.001). Similarly, the survival index was higher in the frozen-intact embryos than in the embryos which were frozen after biopsy (61 versus 38%; P < 0.001). No empty zonae resulted in the control group, while six were found after thawing biopsied embryos. In the second part of the study, blastomere biopsy was implemented on 102 thawed embryos generated by 16 patients. The chromosomal analyses revealed that 49 were normal, leading to the transfer of 2.5 +/- 0.8 embryos per patient. Only three clinical pregnancies were obtained, and are presently ongoing. In conclusion, the present findings discourage the use of conventional cryopreservation protocols in strategies involving preimplantation genetic diagnosis in human reproductive medicine. Adequate protocols are required for freezing and thawing embryos which have been subjected to biopsy procedures.

Adult↗