High pregnancy rate after early human embryo freezing

A flexible protocol for artificial preparation of the endometrium without prior gonadotropin-releasing hormone agonist suppression in women with functioning ovaries undergoing frozen-thawed embryo transfer cycles

OBJECTIVE

To present our experience with a flexible and convenient protocol for artificial endometrial preparation without prior GnRH agonist suppression in patients with functioning ovaries undergoing frozen ET.

DESIGN

Case series.

SETTING

An IVF unit in a university hospital.

PATIENT(S)

All patients who underwent IVF with embryo cryopreservation from December 1997 to June 1998 and requested transfer of their frozen-thawed embryos.

INTERVENTION(S)

Controlled endometrial preparation for ET entailed the use of a fixed dose of 6 mg/d of micronized E2 started on day 1 of the cycle, followed by concomitant administration of micronized P placed in the vagina.

MAIN OUTCOME MEASURE(S)

Hormonal and endometrial profiles throughout the cycle, pregnancy rate per ET, implantation rate, and pregnancy outcome.

RESULT(S)

Of 185 treatment cycles in 140 patients, 8 cycles (4.3%) were canceled. In another 2 cycles, no embryos were suitable for transfer. For the remaining 175 ET cycles, the calculated pregnancy rate and implantation rate were 21.7% and 9%, respectively. The proliferative phase could be extended up to 20 days but was a mean (+/-SD) of 15+/-1.9 days.

CONCLUSION(S)

For patients with functioning ovaries, controlled endometrial preparation for the transfer of frozen-thawed embryos can be done successfully by using oral E2 from day 1 of the cycle followed by P preparation. Prior suppression with GnRH agonist is not necessary.

Contribution of the assisted reproductive technologies to fertility in males suffering spinal cord injury

This study reviews 19 couples referred between 1990 and 1997 for fertility treatment for anejaculatory infertility in the male partner following spinal injury. Using sperm obtained by assisted ejaculation procedures, 14 of the 19 patients (74%) achieved at least 1 pregnancy. Pregnancy rates per treatment cycle were 12.0% for timed intrauterine insemination, 38.9% for gamete intra-Fallopian transfer and 19.2% for intracytoplasmic sperm injection followed by uterine embryo transfer. Choice of the appropriate assisted reproduction treatment to match the available semen quality results in a high level of success in such patients.

Comparison of cryopreservation outcome following intracytoplasmic sperm injection and conventional in vitro fertilization

PURPOSE

Our purpose was to compare the success rate of transferring frozen-thawed embryos generated from either intracytoplasmic sperm injection (ICSI) or conventional in vitro fertilization (IVF).

METHODS

A retrospective review of all frozen-thawed embryo transfer (ET) cycles between January 1995 and April 1997 was performed. There were 83 and 204 transfer cycles of frozen-thawed multicellular embryos generated from conventional IVF (group A) and ICSI (group B), respectively. The survival rate of frozen-thawed embryos and the outcome following ET in both groups were assessed.

RESULTS

The groups did not differ in age (31.7 +/- 4.6 and 30.6 +/- 6.0; mean +/- SD) or number of embryos transferred (3.5 +/- 1.1 and 3.8 +/- 1.3 for groups A and B, respectively). An acceptable pregnancy rate per ET was achieved in both groups, but the rate was significantly higher (P = 0.04) for group A than group B, 32.5 and 20%, respectively. Group A included frozen embryos of a higher quality than those of group B, but the proportion of embryos surviving after thawing was significantly higher for group B than group A (92.5 and 85.6%, respectively; P = 0.0004). The abortion rate did not differ between the two groups: 22 and 26.8% for groups A and B, respectively.

CONCLUSIONS

Although an overall high pregnancy rate was achieved following frozen-thawed ET, it was lower for cycles in which embryos had been generated from ICSI. This difference may be attributed to a lower prefreezing embryo quality in the ICSI group. Embryos originating from ICSI were not vulnerable to cryopreservation and, when implanted, resulted in a comparable abortion rate to thawed embryos of conventional IVF.

Impairment of the developmental potential of frozen-thawed human zygotes obtained after intracytoplasmic sperm injection

OBJECTIVE

To evaluate the effects of cryopreservation on the survival, cleavage, and morphology of embryos and on the implantation and embryonic loss rates of human zygotes obtained after ICSI compared with frozen-thawed zygotes obtained after traditional IVF. A further objective was to evaluate the same parameters in nonfrozen sibling ICSI and IVF zygotes and to compare them with corresponding frozen-thawed zygotes.

DESIGN

Open, retrospective, comparative study.

SETTING

University-associated assisted reproductive program.

PATIENT(S)

Couples with severe male factor infertility and couples undergoing IVF during the same period.

INTERVENTION(S)

A cohort of 408 ICSI zygotes and 299 IVF zygotes was frozen in 1,2 propanediol and sucrose using a slow-freezing protocol. Both groups of zygotes were frozen at approximately the same time after microassisted or conventional insemination. One hundred and eighty-seven ICSI and 110 IVF frozen zygotes were rapidly thawed during 44 ICSI cycles and 24 IVF cycles. Zygotes that appeared to have survived were cultured for 24 hours, and most of these embryos that were morphologically normal were transferred into patients.

MAIN OUTCOME MEASURE(S)

Survival rate (morphologically intact after thawing), cleavage rate and morphology of embryos, implantation rate, and the incidence of embryonic losses.

RESULT(S)

Except for survival rates, for which both ICSI and IVF frozen-thawed zygotes showed similar and relatively high values (87.7% and 89.1%), the outcomes of other parameters evaluated were significantly different. Thus, from a total of 128 ICSI and 68 IVF embryos transferred, 14 (10.9%) and 17 (25.0%) implanted in 44 ICSI and 24 IVF frozen-thawed cycles, respectively. This difference in implantation corresponded with the rate of cleavage and morphology of the replaced embryos; the embryos that developed from frozen-thawed IVF zygotes cleaved faster and were more regular compared to the frozen-thawed ICSI zygotes. The embryonic loss rate was 57.1% for cryopreserved ICSI zygotes and 11.8% for IVF zygotes. On the other hand, no difference in cleavage pattern, embryo morphology, implantation, and embryonic loss rates was found between nonfrozen sibling ICSI and IVF zygotes.

CONCLUSION(S)

The zygotes arising from ICSI cycles survived cryopreservation at a rate similar to IVF zygotes, but their ability to implant and develop further was probably affected by the cryopreservation procedure. The timing of zygote freezing was considered to be the principal reason for the lower developmental potential of frozen-thawed ICSI zygotes in the present study.

Cryopreservation of kunming mouse oocytes using slow cooling, ultrarapid cooling and vitrification protocols

The cryopreservation of oocytes has been only marginally successful with any of the current protocols, including slow cooling, rapid cooling and vitrification. We wished to test the hypothesis that oocytes from a single mouse strain would freeze successfully by 1 of the 3 mentioned protocols. Unfertilized Kunming mouse oocytes obtained 14 h after PMSG/hCG administration were randomly assigned to be cryopreserved after slow cooling, ultra rapid cooling and vitrification. Oocytes were thawed by straws being placed into 37 degrees C water, and their morphological appearance and in vitro fertilization capability were compared with that of oocytes that had not undergone cryopreservation. Survival of oocytes was indicated by the absence of darkened ooplasm or by broken membranes or zona pellucida. Functional integrity was evaluated by the formation of a 2-cell embryo after IVF. Survival rate of slow cooled oocytes did not differ from that seen in vitrified oocytes (55.1 vs 65.9%) but was significantly lower in the rapidly cooled oocytes (24.2%; P < 0.01). The results of IVF of slow cooled and vitrified oocytes were similar to those of the control group (72 and 73 vs 77%; P > 0.05). It appears that Kunming mouse oocytes can be successfully cryopreserved using the slow cooling method with 1,2-propanediol and vitrification, which contains both permeating and nonpermeating cryoprotectants.

Ooplasmic round spermatid nuclear injection procedures as an experimental treatment for nonobstructive azoospermia

PURPOSE

Our objective was to apply ooplasmic round spermatid nuclear injections for the treatment of nonobstructive azoospermia.

MATERIALS

Participants were nine azoospermic men who had previously undergone diagnostic testicular biopsy. Spermatogenetic arrest was diagnosed at the round spermatid stage (n = 6) or primary spermatocyte stage (n = 3). A second (therapeutic) testicular biopsy was performed and round spermatid nuclei were recovered from all the participants.

RESULTS

Forty-nine mature oocytes were successfully injected with nuclei and then cultured for 72 hr. Twenty-four embryos were transferred to nine women. No pregnancy was achieved.

CONCLUSIONS

Round spermatids can be recovered from therapeutic testicular biopsy material of men negative for round spermatids in previous routine diagnostic testicular biopsy specimens. Round spermatid nuclear injections may play a role in the treatment of nonobstructive azoospermia.

Pregnancies after transfer of ultrarapidly frozen human embryos

PURPOSE

We report our experience of freezing human embryos using an ultrarapid freezing method.

METHODS

The patients were superovulated. Oocytes were inseminated and cultured in HTF + 10% serum. A maximum of three embryos was transferred and the rest of the embryos were frozen ultrarapidly after a 3-min equilibration period in PB1 + 3.5 M DMSO + 0.25 M sucrose. Embryos were thawed in a 37 degrees C water bath for 6 sec, then cultured in PB1 + 20% serum for 10 min. The surviving embryos were transferred into patients on the same day of thawing.

RESULTS

Sixty-three embryos were thawed, of which 52 embryos (83%) survived with at least one intact blastomere. Nineteen frozen-thawed embryo transfers were made. The mean embryos per transfer was 2.7. Three pregnancies (16%/transfer) were established. One miscarriage occurred in the eighth week of pregnancy. Two pregnancies went to term and three healthy infants were born.

CONCLUSIONS

The present data demonstrate that ultrarapid freezing is a method worth consideration in the area of human embryo freezing.

Clinical factors for successful cryopreserved-thawed embryo transfer

PURPOSE

To study how clinical factors such as embryo quality, cell stage of embryo at cryopreservation, and synchronization of developmental stages between embryo and endometrium at thawing affect the implantation rate after cryopreserved-thawed embryo transfer (ET), these factors were examined in 106 cryopreserved-thawed ETs including 204 embryos.

RESULTS

In 86 embryos graded as high quality before transfer by morphological evaluation, 31 implantations were successful, while the other, low-quality embryos did not implant at all. High-quality embryos received less cryoinjury during cryopreservation compared to the injuries sustained by embryos in moderate and poor quality. When cyopreservation was performed at the 1-, 2-, and 3-day cell stages, pregnancies were similiarly achieved among most of the embryos at all cell stages. At thawed ETs in natural ovulation cycles, there were some differences among the developmental stages between thawed embryo and endometrium that received the thawed transferred embryos. Although the transfer timelag ranged a day or more, asynchronism of endometrium growth to the cell stage did not reduce pregnancy rates.

CONCLUSIONS

These results indicated that embryo quality evaluated morphologically was the most important clinical factor for successful implantation of cryopreserved-thawed ET.

Successful pregnancy outcome after cryopreservation of all fresh embryos with subsequent transfer into an unstimulated cycle

OBJECTIVE

To assess the pregnancy outcome of freezing and storing all fresh embryos produced in a stimulated IVF cycle and replacing them in a subsequent nongonadotropin-stimulated cycle.

DESIGN

Retrospective study.

SETTING

University-associated assisted reproductive technology program.

PATIENTS

We studied 36 patients (age range 23 to 44 years) who underwent cryopreservation of all fresh embryos in a controlled ovarian hyperstimulation (COH) cycle because of either the risk of severe ovarian hyperstimulation (24 patients, group 1) or the presence of an endometrial lining < 8 mm in thickness (12 patients, group 2). Five hundred fifty-five embryos were generated for replacement in 63 cycles. All embryos were cryopreserved in 1.5 M propanediol at the pronuclear or two-cell stage, and 264 embryos subsequently were transferred into a hormone replacement cycle (70%) or natural ovulatory cycle (30%). The average number of embryos transferred per patient was 4.2.

RESULTS

Twenty-one clinical pregnancies were achieved, giving a pregnancy rate (PR) of 58.3% per patient (33.3% per cycle). The live birth rate was 50% per patient (28.6% per cycle). The implantation rate was 9.1%. Groups 1 and 2 had a similar PR per patient (58.3%). With 208 cryopreserved embryos remaining and considering the 33.3% PR per cycle, we expect the overall extrapolated PR to be 63.9%.

CONCLUSIONS

This is the first series showing that freezing and storing all fresh embryos produced in a stimulated IVF cycle and replacing them in a subsequent nongonadotropin-stimulated cycle results in successful PRs. These results underlie the importance of a successful cryopreservation program in IVF and could be a possible approach to overcoming the alleged adverse effects of COH on the endometrium, thereby improving the chances of pregnancy when numerous embryos are obtained simultaneously.

A simplified method of timing frozen embryo transfers

OBJECTIVE

Our purpose was to compare a simple artificial hormone replacement regimen with two other protocols incorporating pituitary down-regulation with gonadotropin-releasing hormone agonist for frozen embryo transfers.

STUDY DESIGN

We performed a retrospective analysis of pregnancy outcomes after 366 frozen embryo transfers timed by one of three hormone replacement regimens. The three regimens used were regimen A, leuprolide acetate and transdermal estradiol patches; regimen B, leuprolide acetate and oral micronized estradiol; regimen C, only oral micronized estradiol.

RESULTS

The outcomes of 366 consecutive frozen embryo transfers according to one of the three regimens were compared and analyzed. The clinical pregnancy rates were 13.7%, 11.4% and 13.5% in regimens A, B and C, respectively. No statistical differences were found among the three regimens. The mean age of the patients in the three groups was comparable. The mean number of frozen embryos transferred with regimen B was slightly higher, but it did not have a positive impact on the pregnancy rate in this group.

CONCLUSION

Controlled sequential hormone replacement results in an endometrium suitable for frozen embryo transfers. Pituitary down-regulation is not necessary. Therefore this regimen is not only more simple to use but also more economical.

Developmental potential of frozen-thawed human blastocysts

PURPOSE

To examine the possibility of freezing human embryos at late cleaved stages (morula or blastocyst stage), we cryopreserved human embryos 5 days (day 5) or 6 days (day 6) after insemination and investigated their developmental potential after thawing.

MATERIALS AND METHODS

One hundred nineteen morphologically good-quality human embryos from 43 women undergoing in vitro fertilization treatment between 1991 and 1992 were frozen using dimethylsulfoxide as a cryoprotectant. The embryos were cryopreserved for 5 to 30 months. After thawing they were then cultured in vitro for 24 hr to investigate their developmental potential. Survival rates and developmental rates were morphologically assessed after 24 hr of in vitro culture.

RESULTS

Developmental rates were significantly (P < 0.01 or P < 0.05) lower than survival rates at every developmental stage. There was no difference in total survival rates between embryos frozen 5 days after insemination (78.2%; 54/69) and embryos frozen 6 days after insemination (70.0%; 35/54). However, the developmental rates after 24 hr of culture was significantly (P < 0.05) lower for embryos frozen 6 days after insemination (6.0%; 3/50) than for embryos frozen 5 days after insemination (18.8%; 13/69). Only two embryos developed into fetuses after transfer into the uterus (1.7%; 2/119).

CONCLUSIONS

From the results, the developmental potential of frozen-thawed human blastocysts was found to be significantly reduced, even though the blastocysts were of morphologically good quality. Longer in vitro exposure of embryos appears to reduce their developmental potential.

Factors of importance for the establishment of a successful program of intracytoplasmic sperm injection treatment for male infertility

OBJECTIVE

To establish an intracytoplasmic sperm injection treatment program for couples with male infertility and to determine those factors important for success.

DESIGN

A retrospective analysis of 171 consecutive cycles of intracytoplasmic sperm injection concerning 145 infertile couples.

SETTING

Infertility clinic in a private hospital associated with a university hospital.

PATIENTS

Couples with infertility in the male partner whose sperm parameters were unacceptable for conventional IVF or in whom fertilization by conventional IVF failed repeatedly.

INTERVENTIONS

One hundred seventy-one transvaginal oocyte retrievals were completed after superovulation with GnRH agonist and gonadotropins.

MAIN OUTCOME MEASURES

The parameters evaluated included fertilization, cleavage, implantation, pregnancy, and spontaneous abortion in relation to patient indications and improved procedures.

RESULTS

After intracytoplasmic sperm injection, normal fertilization occurred in 45% of the oocytes (n = 1,499). Of 171 treatment cycles, 93% of the couples had fertilization and 86% had ET. Thirty-six pregnancies were achieved. During the period studied, the mean fertilization rate increased from 21.3% during the first 17 weeks to 67.8% during the last 13 weeks, and the pregnancy rate (PR) per started cycle increased from 12.8% to 31.3%.

CONCLUSIONS

Technical factors critical for achieving high rates of fertilization and pregnancy were the use of standardized intracytoplasmic sperm injection pipettes, the immobilization of sperm before injection, and the aspiration of a minimal amount of ooplasm before reinjection with the sperm. Intracytoplasmic sperm injection appears to be superior to other micromanipulation methods for alleviating male infertility.

Tubal versus uterine transfer of cryopreserved embryos: a prospective randomized trial

OBJECTIVE

To compare pregnancy rates after fallopian tubal and uterine transfer of cryopreserved embryos.

DESIGN

Prospective randomized trial with assignment to treatment groups by a random number table.

SETTING

University of Iowa Hospitals and Clinics, a tertiary care academic institution.

PATIENTS

Forty patients with patent fallopian tubes and at least three cryopreserved embryos.

INTERVENTIONS

Cryopreserved embryos were thawed and transferred to the fallopian tube by laparoscopy or to the uterus by a transcervical catheter.

MAIN OUTCOME MEASURES

Clinical and ongoing pregnancy rates.

RESULTS

Tubal transfer of cryopreserved embryos resulted in statistically higher clinical (68% versus 24%) and ongoing pregnancy rates (58% versus 19%) when compared with uterine transfer.

CONCLUSIONS

Tubal transfer of cryopreserved embryos is highly effective and offers an improved pregnancy rate when compared with uterine transfer of embryos. This method of transfer should be considered in patients with patent fallopian tubes and at least three cryopreserved embryos.

Successful implantation of frozen sibling embryos is influenced by the outcome of the cycle from which they were derived

OBJECTIVES

To determine if the success of frozen embryos obtained from assisted reproductive technology (ART) cycles is dependent upon the outcome of the ART cycle from which they were derived and to determine if the length of time in cryostorage affects pregnancy rates (PRs).

DESIGN

Retrospective analysis of pregnancy outcome of consecutive frozen ETs compared with their corresponding "'fresh" cycles.

SETTING

University-affiliated private ART program.

PATIENTS

Between July 1986 and December 1992, 375 oocyte retrieval cycles had at least one subsequent frozen ET for comparison. Of the 375 patients, 94 achieved a clinical pregnancy during their fresh cycle (group A) and 281 patients did not (group B).

INTERVENTIONS

Frozen ETs were performed using either natural (unstimulated) cycles (n = 79) or artificial cycles (n = 296). Transfers during natural cycles were timed with a combination of serum LH levels and ultrasound (US). These transfers were performed 2 days after ovulation. Ovarian suppression with leuprolide acetate followed by sequential estrogen and P replacement were used in the artificial cycles. These transfers were performed on the 3rd day of P administration. Clinical pregnancies were defined as the presence of a gestational sac on transvaginal US.

MAIN OUTCOME MEASURES

Patients were compared based on the pregnancy outcome of their frozen ET cycle and fresh ART cycle. chi 2 analysis and Student's-tests were used to test for statistical significance.

RESULTS

Twenty-three patients (24.1%) from group A achieved a pregnancy from their frozen transfers compared with only 24 patients (8.5%) in group B who achieved a pregnancy from their frozen cycle. PRs did not differ based on the method of follicle aspiration, laparoscopy versus transvaginal US retrieval. Significantly lower PRs were noted in frozen ETs done within the first 10 months after cryopreservation compared with fresh cycle PRs.

CONCLUSIONS

Sibling embryos from a prior successful ART cycle are more likely to initiate a frozen pregnancy and prolonged cryostorage did not affect PRs. This higher PR probably reflects better quality in both fresh and frozen embryos. Therefore, the outcome of the initial cycle can be used to predict the success or failure of subsequent frozen transfers and oocyte-embryo quality appears to be key.

Tuberculous infertility and in vitro fertilization

OBJECTIVES

Our purpose was to assess the outcome of in vitro fertilization and embryo transfer in tuberculous infertility and to study the factors associated with success or failure of treatment.

STUDY DESIGN

Ten patients with tuberculous infertility underwent 22 cycles of in vitro fertilization and 9 cryopreserved-thawed embryo transfers at Bourn Hall Clinic. All patients underwent endometrial assessment by ultrasonography. Four patients had preliminary hysteroscopy, endometrial biopsy, and Doppler uterine blood flow studies.

RESULTS

Six clinical pregnancies resulted in three live births in three patients and one current pregnancy in a fourth patient. There was one ectopic pregnancy and one twin pregnancy that aborted spontaneously at 14 weeks. The patients who had trophic endometrium achieved pregnancy at a rate of 42.9% (six of 14) (per embryo transfer) compared with 0% (none of 14) if the endometrium was atrophic.

CONCLUSION

In vitro fertilization and embryo transfer offers the only realistic treatment for tuberculous infertility. Preliminary assessment of the endometrium is helpful in assessing prognoses in these cases.

Outcome of thaw embryo transfer after cryopreservation of all embryos in patients at risk of ovarian hyperstimulation syndrome

OBJECTIVE

To determine the incidence of ovarian hyperstimulation syndrome (OHSS) and subsequent pregnancy rates (PRs) if ET is delayed in patients at risk of OHSS by allocating all embryos to cryopreservation.

DESIGN

Retrospective analysis of clinical and laboratory data from 724 consecutive stimulated cycles of IVF.

SETTING

University hospital-based IVF program.

PATIENTS

Consecutive patients undergoing IVF between September 1989 and December 1992.

MAIN OUTCOME MEASURES

Fertilization rates, cryosurvival rates, subsequent PRs, and the occurrence of severe OHSS.

RESULTS

Ten of the 564 patients (1.8%) who had ET in the stimulation cycle developed severe OHSS. Sixty-nine patients had all embryos frozen because of the risk of OHSS, of which one (1.4%) developed severe OHSS. The subsequent PR after thaw transfer was 25.2% per transfer, with a cumulative PR per patient after additional thaw transfers of 40.6%.

CONCLUSIONS

Cryopreservation of all embryos and delayed ET in patients at risk of OHSS results in a low incidence of severe OHSS. Oocyte quality, fertilization rates, and cryosurvival of frozen embryos are equal to those for patients who have a normal stimulation profile. Subsequent thaw embryo replacements result in a satisfactory PR.

The protective effects of polymers in the cryopreservation of human and mouse zonae pellucidae and embryos

OBJECTIVES

To evaluate the occurrence of injury due to physical factors in embryo cryopreservation and the effect of the polymers dextran, polyvinylpyrrolidone (PVP), and Ficoll on this mechanical damage.

DESIGN

Damage to the zona pellucida (ZP) observed after cryopreservation was taken as indication of cryoinjury caused exclusively by physical factors. Human and mouse ZPs from oocytes remaining unfertilized after previous IVF attempts and mouse two-cell embryos were frozen in the presence of different polymers. After thawing, they were checked carefully for signs of physical damage (cracks). A possible toxicity of the use of the polymers in cryoprotection was evaluated by development to the blastocyst stage of mouse two-cell embryos that survived the freezing and thawing process.

RESULTS

Incidences of damaged ZPs in groups of human and mouse ZPs and two-cell embryos frozen without polymers were found to vary between 20% and 29%. The use of any of the tested polymers resulted in significantly lower incidences of damaged ZPs (0% to 15%). Damage to the ZP after freezing and thawing in mouse embryos was accompanied by low survival rates of the embryo itself. Of mouse embryos that survived the cryopreservation process, blastocyst formation was not significantly different in groups frozen without polymer (80%) or in the presence of either dextran (90%) or Ficoll (82%); however, embryos frozen in the presence of PVP showed low blastocyst formation (12%).

CONCLUSIONS

Polymers can protect embryos against cryoinjury by avoiding mechanical strain occurring during cryopreservation. Polyvinylpyrrolidine is toxic to mouse two-cell embryos when present during freezing and thawing.

Comparative study of the survival rate of frozen-thawed embryos with perforated zonae from microsurgical fertilization and frozen-thawed embryos with intact zonae

OBJECTIVE

To compare the survival rate of frozen-thawed embryos with perforated zonae from microsurgical fertilization (subzonal insemination) (SUZI) with that of embryos with intact zonae.

DESIGN

Thirty-eight embryos resulting from microsurgical fertilization by SUZI were cryopreserved in 16 patient cycles. Within the same period, 140 zonae-intact embryos from 46 patient cycles were cryopreserved. The survival rate of the SUZI embryos was compared with the zonae-intact embryos after thawing. Clinical pregnancies were compared after the transfer of the thawed embryos.

RESULTS

The total survival rates were 94.7% and 89.3% for thawed SUZI embryos and zonae-intact embryos, respectively. Within each type of embryo, total survival rates were similar irrespective of the age of the embryos at freezing. The blastomere loss per thawed embryo was the same for zonae-intact and SUZI embryos. One clinical pregnancy was obtained in patients who received thawed SUZI embryos and nine in patients who received embryos with intact zonae.

CONCLUSIONS

It is concluded that SUZI embryos can be cryopreserved and thawed with the same degree of confidence as zonae-intact embryos. The low implantation rate of thawed SUZI embryos requires confirmation in a larger clinical series.

Cytogenetic, cellular, and developmental consequences of cryopreservation of immature and mature mouse and human oocytes

This study examined the effects of cryopreservation on cellular organization, chromosomal complement, and developmental potential of immature and mature mouse and human oocytes. Chromosomal analyses were performed by DNA fluorescence microscopy and karyotyping on the same metaphase II-stage oocytes before and after freezing. Cellular analyses involved electron microscopy, time-lapse video recording, and fluorescent-probe microscopy of cortical granules. The findings demonstrate that while profound cytoplasmic, nuclear, and nucleolar alterations occur in the immature oocyte during cryopreservation, an apparently normal nucleus and cytoplasm is re-established progressively after thawing and culture. The resulting oocytes mature at high frequency and for the mouse, are fertilizable and capable of normal preimplantation of embryogenesis. Cryopreservation of mature mouse and human oocytes is not accompanied by a significant increase in the frequency of aneuploidy. However, cryopreserved human oocytes, while fertilizable, arrest development during the early cleavage stages and display aberrant patterns of cytokinesis. The possible etiologies of developmental failure in the human embryo that may be related to oocyte cryopreservation, as well as the potential benefits of cryopreservation of the immature oocyte, are discussed with respect to clinical and commercial applications.

Significantly enhanced pregnancy rates per cycle through cryopreservation and thaw of pronuclear stage oocytes

OBJECTIVE

To examine the results of a 5-year trial using cryopreservation to limit multiple pregnancy and optimize overall pregnancy per cycle.

DESIGN

Retrospective clinical evaluation of pregnancy rates (PRs) per cycle after freezing pronuclear stage human oocytes.

SETTING

Tertiary care academic center.

PATIENTS

Six hundred seventeen patients treated in 776 IVF-ET cycles from January 1987 to December 1991 (less oocyte donation cycles).

MAIN OUTCOME MEASURE

Pregnancy rate per cycle after transfer of pre-embryos developed from thawed pronuclear stage oocytes.

RESULTS

Three thousand seven hundred thirty-one oocytes were frozen. Of these, 2,039 were thawed. One thousand three hundred seventy-seven survived thawing (68%), and 1,370 were transferred after passing through syngamy to at least the first cleavage (68%). Of patients with thawing, 359 of 401 (90%) (449 of 505 cycles [89%]) received intrauterine transfer. One hundred thirty-three separate clinical pregnancies were established from 128 different cycles (128/449; 29%); 5 cycles had two thaws, each of which resulted in pregnancy. This PR is less than the overall fresh PR observed in patients who had excess pronucleate oocytes frozen (279/776; 36%) but is remarkably similar when adjusted for the number of pre-embryos transferred per cycle. The age of the patient at the time of cryopreservation and the number of quality of pre-embryos ultimately available for transfer were important factors in the establishment of pregnancy. The mode of ovarian stimulation and duration of cryostorage did not prove meaningful.

CONCLUSIONS

Cryopreserved pronucleate oocytes that survive freezing, thawing, and progress through syngamy demonstrate a similar potential for implantation and pregnancy when compared with fresh conceptuses, the cumulative effect of which is an enhanced total PR per cycle.

The effect of maternal serum on phase-change temperature in human embryo cryopreservation

The effect of addition of maternal serum to cryomedium on the phase-change temperature for embryo cryopreservation has been investigated. No effect on the eutectic point (i.e., earliest seeding temperature) was found within patients because of serum concentration or the time in the ovarian cycle when the serum was collected. However, the optimum seeding temperature did vary between patients, which suggests that self-seeding devices for embryo cryopreservation may be practically beneficial.

Comparison of cycle outcome for gamete intrafallopian transfer alone and in combination with intrauterine embryo transfer

As an alternative to embryo cryopreservation, the efficacy of intrauterine transcervical transfer of a small number of embryos resulting from fertilization of supernumerary oocytes obtained during a GIFT cycle (GIFT-ET) was assessed in this investigation. Data from 72 consecutive GIFT (N = 27) and GIFT-ET (N = 45) cycles were retrospectively reviewed. Age and infertility diagnoses were similar among the two groups. Clinical pregnancy, ongoing pregnancy, and abortion rates per retrieval were not significantly different between the two groups. We conclude that GIFT-ET offers no advantage over GIFT alone and that cryopreservation of all supernumerary embryos with intrauterine transfer in subsequent cycles would maximize pregnancy rates from a single oocyte aspiration and GIFT procedure.

The effects of cryopreservation on early development and chromosome constitution in Chinese hamster embryos

The effects of cryopreservation on early embryonic development were investigated in Chinese hamster embryos. Embryos were randomly divided into 3 groups, as follows: the control group, embryos which were simply cultured; the DMSO group, embryos which were exposed to dimethyl sulfoxide (DMSO) and then cultured; the cryopreservation group, embryos which were cryopreserved and then cultured. The percentages of embryos which developed into blastocysts after 40 hours of cultivation were high in all groups. However, there were significant differences in the mean number of blastomeres with lower values after an exposure to DMSO and cryopreservation (73.2 in the control group, 62.0 in the DMSO group, and 40.2 in the cryopreservation group). No significant differences in chromosome abnormality rate were evident and there was no distinct tendency for variation in karyotype among the 3 groups. These results indicate that DMSO adversely affects the division of blastomeres, and that cryopreservation with DMSO as a cryoprotectant might aggravate these adverse effects.

Freezing cocultured human blastocysts

OBJECTIVE

To determine the possibility of obtaining good pregnancy rates (PRs) after freezing and thawing cocultured blastocysts.

DESIGN

Human blastocysts were frozen first according to a protocol available from literature. Two other protocols including the addition of glycerol were designed to improve the results.

SETTING

All the patients were under clinical management at the Institut Rhonalpin pour l'Etude de la Reproduction Humaine in Lyons, France.

PATIENTS

Patients involved in the in vitro fertilization program have had their supernumerary embryos frozen according to the three protocols presented here.

MAIN OUTCOME MEASURES

Embryo recovery after freezing and thawing. Clinical and ongoing pregnancies after embryo transfer (ET).

RESULTS

A protocol including sucrose addition and reduction of steps in the preparation of the blastocysts for freezing gave us a 21% PR per transfer (15 ongoing) of 101 transfers (106 thawings).

CONCLUSIONS

Freezing of cocultured human blastocysts allow good PRs. This can represent an alternative for repeated failures of ETs at early stages.

Exogenous control of the cycle simplifies thawed embryo transfer and results in a pregnancy rate similar to that for natural cycles

To determine if a satisfactory PR could be achieved in thawed ET using a simplified protocol, standard monitoring in the natural cycle was compared with a controlled preparation of the endometrium with exogenous E2 and P without hormonal or ultrasonographic monitoring. All patients had normal ovarian function, and no GnRH-a were administered. Pregnancy rates, ongoing PRs, and embryo implantation rates were similar in the two groups. The use of exogenous E2 and P without GnRH-a suppression to control the cycle for thaw ET is safe, convenient, and results in PRs at least as good as in the natural cycle. It may be of particular value in patients with an irregular cycle or in those for whom prolonged monitoring is undesirable.

Survival of human oocytes cryopreserved with or without the cumulus in 1,2-propanediol

BACKGROUND

Although cryopreservation of human preembryos has been carried out with success, the cryostorage of oocytes, which pose fewer controversial moral, ethical, and legal problems has been much less successful. Various attempts to cryopreserve human oocytes have been mostly unsuccessful and the search for an optimal protocol for oocyte cryopreservation remains elusive. We therefore undertook this study to determine the effect of oocyte cryostorage in 1,2-propanediol.

METHOD

Mature human oocytes with or without their cumuli were cryopreserved in precooled 1,2-propanediol, then thawed and inseminated with sperms for in vitro fertilization. The outcome of insemination and subsequent embryonic development were also recorded and compared.

RESULTS

Postthaw cryosurvival rate was significantly better when cryostorage was carried out with the oocyte cumulus intact as compared to those oocytes denuded of their cumuli (54 versus 27%, respectively; P < 0.05). Eight (44%) of 18 surviving postthaw oocytes with intact cumuli were fertilized normally, with cleavage in six, as compared to two (25%) and one, respectively, of those denuded of their cumulus prior to cryostorage. Development to the blastocyst stage was achieved in three embryos derived from oocytes with an intact cumulus at cryostorage.

CONCLUSION

We conclude that 1,2-propanediol can be used with success in oocyte cryopreservation, although the issue of parthenogenecity is still to be resolved. Oocyte's with intact cumulus survive cryostorage better than those without it.

In vitro fertilization as a diagnostic and therapeutic tool in a patient with partial 17,20-desmolase deficiency

OBJECTIVE

To present a case with 17,20-desmolase activity deficiency in which in vitro fertilization (IVF) served not only as a therapeutic approach but also as a diagnostic tool for the specificity of the enzymatic deficiency.

DESIGN

IVF in the patient under study compared with a control group. All women treated with pure follicle-stimulating hormone (FSH).

SETTING

IVF program at the Instituto Valenciano de Infertilidad.

PATIENTS, PARTICIPANTS

A patient with primary amenorrhea, who was the subject under study, and seven normally cycling control patients undergoing IVF in the same series.

INTERVENTIONS

IVF, steroidogenesis in vitro of granulosa-luteal cell obtained at ovum pick-up.

MAIN OUTCOME MEASURE(S)

Oocyte fertilization and embryo cleavage. Serum and follicular fluid (FF) levels of estradiol (E2), progesterone (P), testosterone (T), androstendione (A), 17 alpha-hydroxyprogesterone (17-OHP). In vitro accumulation of E2 and P.

RESULTS

Ovulation induction with FSH was successful in achieving follicular development despite low circulating E2. Fertilization and cleavage rates were similar to the control subjects. The patient developed ovarian hyperstimulation. The lack of 17,20-desmolase activity was detected by normal P levels in serum and FF, high 17-OHP, and low T, A, and E2 levels in serum and FF. Granulosaluteal cell cultures in the presence of T restored normal E2 and P production in response to gonadotropins.

CONCLUSIONS

In patients with 17,20-desmolase deficiency, follicular development, oocyte maturation, and fertilization can take place in a low estrogenic environment.

The effect of cryopreservation on the development of S- and G2-phase mouse embryos

The survival rate and development of four-cell-stage mouse embryos frozen and thawed in S phase versus G2 phase was compared. Significantly more G2-phase than S-phase embryos survived freezing and thawing. In both groups, disruption of the zona pellucida, fusion of blastomeres, and dispersion of chromosomes were occasionally observed after thawing. Cryopreservation resulted in a longer delay in cleavage from the four- to the eight-cell stage of S (about 5 hr)- and G2-phase embryos (about 3 hr) compared to unfrozen controls. The number of frozen embryos which developed to the blastocyst stage was reduced compared to controls, and in the case of S-phase embryos, formation of the blastocyst cavity was also delayed. However, the average number of cells in the experimental and control embryos was similar. No increased incidence of chromosome abnormalities was seen. Our results suggest that freezing embryos in G2 is superior to freezing in S phase.

Alterations in luteal phase progesterone and estradiol production after leuprolide acetate therapy before ovarian stimulation for in vitro fertilization

The impact of pituitary suppression with a gonadotropin-releasing hormone agonist (GnRH-a) on the luteal phase of in vitro fertilization (IVF) cycles was examined in 21 women who underwent identical stimulation regimens with and without leuprolide acetate pretreatment. The areas under the serum progesterone curves, measured over the 1st 10 days of the luteal phase, were significantly greater in the GnRH-a cycles compared with the non-GnRHa cycles, but when calculated per oocyte retrieved were similar in GnRH-a and non-GnRH-a cycles. In contrast, the areas under the luteal phase serum estradiol curves were significantly less in the GnRH-a cycles. These data suggest that GnRH-a treatment is accompanied by potentially beneficial alterations in the systemic steroidal milieu of the luteal phase of IVF cycles.

Pregnancy potential of human oocytes--the effect of cryopreservation

BACKGROUND

In vitro fertilization, sometimes involving the cryopreservation of human embryos, has become a routine procedure for the treatment of infertility. Even though there are embryos available for transfer in about 85 percent of the treatment cycles, the rate of pregnancy rarely exceeds 25 percent per cycle. We designed this study to investigate two questions: Does this high rate of failure result from inadequate technique, or does it simply reflect the maximal potential of a cohort of aspirated eggs to produce a pregnancy? And to what extent does cryopreservation affect the capacity for implantation of embryos?

METHODS

The study was conducted among patients enrolled in an egg-donation program. Aspirated eggs from a given cohort were distributed to the donor herself and a few recipients. The recipients were prepared by a standard protocol of hormone replacement and were assigned at random to the transfer of either fresh or frozen and thawed embryos. The donors received only fresh embryos.

RESULTS

Forty cycles of donation were studied. In 25 cycles (63 percent) pregnancy was established in the donor, in the recipient (or recipients), or in both. Of the fresh embryos that were transferred to the recipients, 24 percent were successfully implanted, as compared with only 7.7 percent of the frozen and thawed embryos (P less than 0.01). A pregnancy success rate of 37 percent per recipient cycle was observed in the recipients of fresh embryos, as compared with a rate of only 16 percent in those receiving frozen and thawed embryos (P less than 0.05).

CONCLUSIONS

The majority of egg cohorts evidently possess the potential to produce a pregnancy, but cryopreservation of human embryos significantly reduces their capacity for implantation.

Different implantation rates after transfers of cryopreserved embryos originating from donated oocytes or from regular in vitro fertilization

Most oocyte donation programs have experienced higher pregnancy rates than usually seen in regular in vitro fertilization (IVF), suggesting that the quality of either the oocytes or the endometrium is superior. To clarify this issue we analyzed the results of transfers of 136 cryopreserved embryos originating either from donated oocytes (18 transfers) or from regular IVF (118 transfers). Transfers of embryos originating from donated oocytes took place after administrating oral estradiol (E2) valerate and vaginal micronized progesterone (P) following a regimen designed to mimic the serum levels of E2 and P observed during the menstrual cycle. Transfers of embryos originating from regular IVF took place either in the natural cycle (53 transfers) or after suppressing ovarian function with a single injection of a gonadotropin-releasing hormone agonist (GnRH-a), Decapeptyl-Retard 3.75 mg, and administering the same hormone replacement regimen (E2/P) used in oocyte donation (65 transfers). Eighteen transfers involving 24 embryos originating from donated oocytes were affected, resulting in six pregnancies (4 ongoing). The ongoing pregnancy rate per transfer was 22%. Seventy-nine embryos originating from regular IVF were transferred (53 transfers) in the natural cycle resulting in six pregnancies (2 ongoing). One hundred three other embryos originating from regular IVF were transferred (65 transfers) after administration of GnRH-a and E2/P resulting in four pregnancies. The pregnancy rate after transfers of embryos originating from regular IVF was 9% per transfer. This was significantly less than the pregnancy rate of 33% per transfer seen after the transfers of embryos originating from donated oocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Successful ultrarapid freezing of unfertilized oocytes

Successful application of ultrarapid freezing techniques to unfertilized murine oocytes has not been reported. In an effort to improve results, preovulatory murine oocytes were exposed to three ultrarapid freezing protocols involving varying sucrose concentrations (0.25, 0.5, and 1.0 M) and 3.5 M dimethyl sulfoxide (DMSO) as cryoprotectants prior to direct immersion in liquid nitrogen. Post-thaw morphology and rates of in vitro fertilization and embryo development were compared with those obtained after freezing oocytes employing two established programmed cooling techniques. The rates of fertilization and development to the blastocyst stage in vitro of oocytes undergoing ultrarapid freezing after exposure to 3.5 M DMSO and 0.5 M sucrose were similar or superior to those obtained with programmed cooling techniques. Of oocytes which appeared morphologically normal post-thaw, only those which underwent ultrarapid freezing with 0.25 or 0.5 M sucrose and 3.5 M DMSO reached the blastocyst stage at rates similar to those of controls. Ultrarapid freezing may represent a viable option for successful murine oocyte cryopreservation.

Follicular development and oocyte maturation after stimulation with gonadotropins versus leuprolide acetate/gonadotropins during in vitro fertilization

Follicular development and oocyte maturation were compared in 22 patients stimulated with human menopausal gonadotropins/human chorionic gonadotropin (hCG, group I) and in 52 women also treated with the gonadotropin-releasing hormone agonist (GnRH-a) leuprolide acetate (LA, group II). Suppression of endogenous leutinizing hormone (LH) surges by LA allowed delayed hCG administration, resulting in higher peripheral estradiol levels, more retrieved oocyte cumulus corona complexes, and greater numbers of cryopreserved embryos. Reduction in spontaneous LH surges in the GnRH-a cycles may have allowed time for larger follicular fluid (FF) volume accumulation during all phases of oocyte cumulus corona complex maturation, restoring synchrony between FF volume and oocyte cumulus corona complex maturity.

The management of predicted ovarian hyperstimulation involving gonadotropin-releasing hormone analog with elective cryopreservation of all pre-embryos

Severe ovarian hyperstimulation syndrome complicates up to 6% of IVF treatment cycles. We have utilized our pre-embryo cryopreservation program to manage incipient ovarian hyperstimulation syndrome in an alternative way. Four women, who were at risk of developing ovarian hyperstimulation syndrome, underwent oocyte retrieval, but not embryo replacement. Instead, resulting pre-embryos were cryopreserved for future transfer. The four patients have since become pregnant. Three conceived after thawed embryo replacement cycles, and the fourth conceived spontaneously 1 month after the stimulation cycle. This approach offers maximum flexibility in the management of ovarian hyperstimulation syndrome.

A protocol for satisfying the ethical issues raised by oocyte donation: the free, anonymous, and fertile donors

A new protocol was developed to provide participants of our oocyte donation program with oocytes donated by donors who were not financially rewarded, were anonymous, and fertile. Each participant provided an oocyte donor selected among fertile friends or family members. The retrieved oocytes were anonymously exchanged between phenotypically matched donor-recipient pairs. In the first 30 months of activity, we obtained 111 embryos suitable for transfer or cryopreservation from 52 retrievals, and 40 embryo transfers (ETs) were performed. Recipients received oral Estradiol-valerate and vaginal micronized progesterone. Fifteen embryos were transferred in 8 ETs conducted after donor-recipient synchronization. This resulted in four pregnancies, all ongoing (ongoing pregnancy rate 50% per transfer). Of the 96 cryopreserved embryos, 82 were thawed for ET, and 45 surviving embryos were transferred in 32 ETs. This resulted in eight pregnancies, with six ongoing or delivered (ongoing pregnancy rate 19% per transfer). The overall ongoing pregnancy rate of 25% per transfer indicates that our approach is a viable method for obtaining donated oocytes while respecting the ethical guidelines that recommended that donation of human gametes should be free, and from anonymous and fertile donors. Furthermore, guaranteeing anonymous oocyte donation had practical importance because, for many volunteer donors, it played a crucial role in their decision to donate.

Parthenogenetic activation of unfertilized mouse oocytes by exposure to 1,2-propanediol is influenced by temperature, oocyte age, and cumulus removal

Cumulus-intact and -denuded unfertilized oocytes from two mouse strains were exposed to 1.5 M ethanol (EtOH) or two cryoprotectant solutions, 1.5 M propanediol (PROH) or 1.5 M dimethylsulfoxide (DMSO), for 4.5 min at 27 degrees C, and the proportion of activating or degenerating oocytes studied. Exposure to DMSO did not significantly increase activation above that of oocytes not exposed to DMSO. Treatment of oocytes in PROH resulted in the activation of up to 87% of viable oocytes. This was significantly higher (P less than .01) than in control oocytes and comparable to the rate of activation after treatment with EtOH (59-96% activation). In solutions at 1 degree C, 47% of control oocytes were activated, which was not significantly different from the rate of activation in EtOH (36%) or PROH (50%) at 1 degree C. Following treatment with PROH, up to 87% of oocytes degenerated within a period of 6 h in vitro. The age of the oocytes (h post hCG) and the time of cumulus removal with the enzyme hyaluronidase, relative to the time of exposure to the chemicals, influenced the level of degeneration in most groups. Significantly fewer oocytes degenerated when cumulus cells were removed before treatment (0-31%) than when the cumulus was left intact throughout the treatment and 6 h culture period (10-87%). Exposure to PROH at 1 degree C reduced oocyte degeneration to 5%. We conclude that PROH causes significantly greater losses of oocytes as a result of parthenogenetic activation and degeneration than of exposure to DMSO.

Development of human male pronucleus: ultrastructure and timing

The process of human male pronuclear formation was studied using an experimental model based on in vitro inseminated human zona-free eggs prepared from oocytes that failed to fertilize in a clinical in vitro fertilization program. The main ultrastructural changes in penetrated sperm nuclei transforming pronuclei were used to define four stages of pronuclear development. The first two stages, representing partial (Stage 1) and total (Stage 2) sperm chromatin decondensation, appeared as early as 1 hr after mixing of gametes. This rapid initial phase was followed by a more lengthy array of events leading to transformation of decondensed sperm nuclei into fully developed male pronuclei (Stages 3 and 4). Stage 3 was characterized by reformation of the nuclear envelope, reorganization of chromatin, and the assembly of nucleolar precursors. It was not completed until 12 hr after in vitro insemination when fully developed male pronuclei (Stage 4) were first observed. In some eggs pronuclei did not reach Stage 4 at all. The results of this study provide a morphological background for further research into molecular aspects of human male pronuclear development and its regulation.

Transfer of cryopreserved-thawed embryos: the natural cycle versus controlled preparation of the endometrium with gonadotropin-releasing hormone agonist and exogenous estradiol and progesterone (GEEP)

Modeled on our successful experience with oocyte donation, we present a novel, viable approach to cryopreserved-thawed embryo transfers (ETs) in women with recalcitrant ovarian dysfunction: gonadotropin-releasing hormone agonist and exogenous estradiol and progesterone (GEEP). After attainment of ovarian suppression, seven such women received physiological steroidal replacement regimens with cryopreserved-thawed ETs prospectively synchronized with the 4th day of progesterone administration and two conceived. These GEEP cycles and cryopreserved-thawed ETs were prospectively compared with cryopreserved-thawed ETs performed on the 4th day of exposure to progesterone in 20 spontaneous cycles and in 5 oocyte donation-steroidal replacement cycles. Pregnancies occurred after three cryopreserved-thawed ETs in each of these groups. We conclude that GEEP constitutes a successful preparation for cryopreserved-thawed ETs, at the least, in women with ovulatory dysfunction.

Supplementation of in-vitro fertilisation culture medium with platelet activating factor

The supplementation of culture medium with platelet activating factor (PAF) on the subsequent implantation and pregnancy potential of pre-embryos produced by in-vitro fertilisation was studied. Pre-embryo culture medium was supplemented with 0 (control), 0.186, 0.93, or 1.49 mumol/1 PAF. Pre-embryos were transferred to PAF-containing medium 15-17 h after insemination (ie, just before syngamy) for 24 h and then transferred to the uterus. For 185 women receiving control pre-embryos, the pregnancy rate (positive beta human chorionic gonadotropin per oocyte retrieval) was 10.2%, while 166 women who received PAF treated pre-embryos (all concentrations combined) achieved a pregnancy rate of 17.5%. This difference was significant. The pregnancy rates per pre-embryo transferred were 6.1% and 9.4% for the control and PAF groups, respectively. The percentage of positive pregnancy tests that resulted in a viable pregnancy (presence of fetal heart at 8 weeks) was 78.9% in the controls and 75.9% in the PAF group. There was no difference in the average number of embryos transferred in either group. The increase in the pregnancy rate after a short exposure of pre-embryos to PAF in vitro suggests that PAF mediates pre-embryo development.

Pregnancy in women with premature ovarian failure using tubal and intrauterine transfer of cryopreserved zygotes

Twenty-nine women, mean age 36.3 (SD 5.5) years, with premature ovarian failure received donated ova on an ovum donation programme. Three had Turner's syndrome, four a surgical menopause, one a chemotherapy-induced menopause and 21 had idiopathic premature ovarian failure. All donated oocytes were fertilized with frozen-thawed spermatozoa from the recipient's partner, and the resulting zygotes were frozen until transfer had been arranged. Overall, 19 women had intrauterine embryo transfer (ET) and a mean of 2.7 (SD 0.9) embryos were transferred on 20 occasions; 10 women underwent zygote intrafallopian transfer (ZIFT) and a mean of 3.5 (SD 0.5) zygotes were transferred on 10 occasions. Both groups were matched for age. The pregnancy rate per transfer was 20% in the ET group and 40% in the ZIFT group. After excluding the 10 women in the ET group who had fewer than three embryos transferred, the pregnancy rates were similar in the two groups, 30% in the ET group and 40% in the ZIFT group. Cryopreserved embryos may be used for ovum donation to preserve anonymity and still show a high pregnancy rate of at least 30% per transfer.

Hamster oocyte penetration tests with oocytes frozen in propanediol: comparison with non-frozen oocytes

Hamster oocytes were frozen using a 1,2-propanediol-sucrose procedure, which resulted in over 90% survival. After thawing and zona removal the oocytes were compared with non-frozen oocytes in a zona-free hamster egg test employing spermatozoa from human semen donors and suspected infertility patients. Similar data were obtained, indicating that propanediol-sucrose frozen hamster eggs may be used in place of fresh eggs for convenience and to avoid scheduling problems.

The effect of prefreeze in vitro culturing on the success of embryo freezing in mice

There is currently a controversy as to whether the prolonged in vitro culturing of embryos before freezing has a deleterious effect on their ability to survive freezing and thawing. We compared the survival rate of frozen/thawed mouse embryos after in vitro culturing, from the two-cell stage through the eight-cell, morula, and blastocyst stages, with the survival of embryos developed in vivo to the same stages. Following induced superovulation and mating, embryos in the desired cleavage stage were flushed from the oviducts and/or uterus and either cultured in vitro or frozen immediately in sterile glass ampoules to -40 degrees C and plunged into liquid nitrogen for storage. Dimethyl sulfoxide (1.5 M) was used as cryoprotectant. After thawing, the survival rate (determined by the morphological appearance of the embryos) was significantly lower in the eight-cell stage embryos in the group grown in vivo (P less than 0.05). The number of embryos developing into expanded and hatched blastocysts was not significantly different when the in vivo vs in vitro cultures were compared over each of the three cleavage stages: eight cells (82 vs 83%), morula (92 vs 87%), and blastocyst (33 vs 51%), respectively. There was a significant decrease in the development rate of blastocyst-stage embryos when compared with earlier stages under both culture conditions (P less than 0.001). It is concluded that, compared to in vivo-grown embryos frozen at the same stages, prolonged in vitro culture does not reduce the embryos' ability to develop normally.

Human embryo viability after freezing with dimethylsulfoxide as a cryoprotectant

This study concerns the effects of a slow freezing and thawing protocol using dimethylsulfoxide (DMSO) as a cryoprotectant on the survival and viability of 319 supernumerary human embryos produced after in vitro fertilization. One hundred twenty-one transfers were performed in a natural cycle and 18 pregnancies were achieved (15%), from which 14 were ongoing (12%). Overall, 52% of the thawed embryos retained at least 50% of their initial blastomeres intact after thawing, and were replaced. Survival was strongly correlated to prefreezing embryonic quality, as 78% of type I embryos, 55% of type II, 40% of type III, and none of type IV could be transferred. Implantations were obtained from type I embryos (21% per embryo replaced) and from type II (14.5%), whereas none of the type III embryos resulted in a pregnancy. In the authors' experience, using the DMSO protocol, the best pregnancy rates were achieved when replacing 8-cell embryos of high morphologic prefreezing quality. No statistically significant difference could be demonstrated, however, in implantation rates between 8-cell and 4-cell embryos, or between synchronously and asynchronously dividing concepti.