Elective single embryo transfer (eSET) policy in the first three IVF/ICSI treatment cycles

BACKGROUND: Elective single embryo transfer (eSET), applied in the first or second IVF cycle in young patients with good quality embryos, has been demonstrated to lower the twin pregnancy rate, while the overall pregnancy rate is not compromised. It is as yet unclear whether eSET could be the preferred transfer policy in all treatment cycles, or that it should be restricted to the first or first two cycles. METHODS: eSET policy (when two or more embryos were available, at least one of them being of good quality) was offered to patients younger than 38 years in the first three treatment cycles. Retrospectively, treatment cycle outcome was studied. RESULTS: In 326 patients, 586 treatment cycles were performed (326 first, 168 second and 92 third treatment cycles). In 65 cycles (11%), eSET could not be applied because there was either no fertilization, or only one embryo available. In the remaining 521 cycles, eSET was performed in 111 cycles (19%), while in 410 cycles, no good quality embryo was available resulting in the transfer of two embryos (double embryo transfer, DET). No significant differences in ongoing pregnancy rates after transfer of fresh embryos were observed between eSET and DET in the first (both 33%), second (36 and 23%, respectively) and third treatment cycles (20 and 24%, respectively). In significantly more eSET cycles compared to DET cycles, could embryos be frozen. This resulted in a significantly higher cumulative pregnancy rate after eSET compared to DET. CONCLUSIONS: In patients younger than 38 years with at least one top quality embryo, eSET can be the transfer policy of choice in at least the first three treatment cycles, since the pregnancy rates obtained in each treatment cycle are comparable to those after DET.     

A real-life prospective health economic study of elective single embryo transfer versus two-embryo transfer in first IVF/ICSI cycles

BACKGROUND: We analysed the difference in maternal, neonatal and total costs after single (SET) versus double day 3 embryo transfer (DET). METHODS: We performed a two-centre prospective study of women in their first IVF/ICSI cycle choosing between SET or DET. Infertility treatment data were gathered from a database; maternal and neonatal outcome data from a case report form (CRF); health economic data from medical acts registered in the CRF for the outpatient part and from hospital bills. SET was performed in 206/367 (56.1%) and DET in 161/367 (43.9%) women. RESULTS: In all, 367 transfers yielded 186 positive pregnancy tests, 148 ongoing pregnancies and 136 live deliveries (50.7, 40.3 and 37.1% per embryo transfer) of which 15 (11.0%) were twins. Live birth rate was 37.4% for SET, 36.6% for DET. Intention-to-treat analysis showed differences for: duration of pregnancy (SET: 39.0 +/- 1.4 versus DET: 38.3 +/- 2.2 weeks; P = 0.055), percentage prematurity (8.5 versus 23.8%; P = 0.033), percentage of neonates hospitalized (5.7 versus 17.9%; P = 0.121) and duration of neonatal hospitalization (6.3 +/- 2.2 versus 10.3 +/- 10.1 days; P = 0.01). Total cost after DET was higher (SET: 4700 +/- 3239 versus DET: 8613 +/- 10 105; P = 0.105), due to significantly higher neonatal costs (451 +/- 957 versus 3453 +/- 8154; P < 0.001) and not to differences in maternal costs (4250 +/- 2882 versus 5160 +/- 4106; P = 0.152). CONCLUSIONS: This prospective health economic study shows that transfer of a single top quality embryo is equally effective as, but substantially cheaper than, double embryo transfer in women <38 years of age in their first IVF/ICSI cycle.     

The psychological impact of IVF failure after two or more cycles of IVF with a mild versus standard treatment strategy

BACKGROUND: Failure of IVF treatment after a number of cycles can be devastating for couples. Although mild IVF strategies reduce the psychological burden of treatment, failure may cause feelings of regret that a more aggressive approach, including the transfer of two embryos, was not employed. In this study, the impact of treatment failure after two or more cycles on stress was studied, following treatment with a mild versus a standard treatment strategy. METHODS: Randomized controlled two-centre trial (ISRCTN35766970). Women were randomized to undergo mild ovarian stimulation (including GnRH antagonist co-treatment) and single embryo transfer (n = 197) or standard GnRH agonist long-protocol ovarian stimulation with double embryo transfer (n = 194). Participants completed the Hospital Anxiety and Depression Scale prior to commencing treatment and 1 week after the outcome of their final treatment cycle was known. Data from women who underwent two or more IVF cycles were subject to analysis (n = 253). RESULTS: Women who experienced treatment failure after standard IVF treatment presented more symptoms of depression 1 week after treatment termination compared with women who had undergone mild IVF: adjusted mean (+/-95% confidence interval) = 10.2 (+/-2.3) versus 5.4 (+/-1.8), respectively, P = 0.01. CONCLUSIONS: Failure of IVF treatment after a mild treatment strategy may result in fewer short-term symptoms of depression as compared to failure after a standard treatment strategy. These findings may further encourage the application of mild IVF treatment strategies in clinical practice.     

Outcome of conventional IVF and ICSI on sibling oocytes in mild male factor infertility

BACKGROUND: Decisions concerning the treatment choice for assisted reproduction (IVF or ICSI) are usually made after the evaluation of male fertility factors, or after taking into account the results of previous IVF attempts. There are no widely accepted criteria, so decisions for couples with male subfertility are often empirical and may lead to complete fertilization failure after IVF, or to the unnecessary use of ICSI. METHODS: A study was conducted in which half the oocytes from each of 58 couples with moderate oligo +/- astheno +/- teratozoospermia were inseminated (conventional IVF) and the other half microinjected (ICSI). The technique used for subsequent cycles depended on the results of the first cycle. RESULTS: Nineteen of the 58 IVF/ICSI attempts resulted in fertilization after ICSI only (32.8%) and 39 in fertilization after IVF and ICSI (67.2%). For patients with oocyte fertilization only after ICSI, 61.5% of the oocytes microinjected were fertilized. A mean of 2.2 embryos per patient were transferred, leading to eight clinical pregnancies (42.1%).The implantation rate was 21.4%. All subsequent cycles were carried out with ICSI. Couples with oocyte fertilization after both IVF and ICSI had slightly better semen characteristics than those with oocyte fertilization only after ICSI, but this difference was not significant. Overall, no statistically significant difference was observed between IVF and ICSI in sibling oocytes for any of the variables studied: fertilization rate, embryo morphology and rates of development, pregnancy and implantation. Although only small numbers of oocytes or embryos were available for each couple, six couples had lower fertilization rates after IVF and eight had lower embryo quality after IVF. Eight patients had lower sperm quality in the second cycle, and only seven couples underwent subsequent IVF cycles. CONCLUSIONS: This strategy enabled us to avoid 32.8% of complete fertilization failures after IVF, but not to decrease significantly the number of ICSI attempts in subsequent cycles. However, the uncertainties concerning the safety of ICSI suggest that ICSI should be used cautiously and judiciously.     

Developmental competence of oocytes after ICSI in the rhesus monkey

Oocyte quantity and quality are critical to assisted reproductive technology (ART), yet few assessments beyond counting metaphase II (MII) oocytes exist. In this study, 30 +/- 2 oocytes per cycle were recovered from rhesus monkeys subjected to follicular stimulation with human gonadotrophins, of which 15 +/- 1 were MII. Oocyte quality was investigated by monitoring the developmental potential of oocytes subjected to intracytoplasmic sperm injection (ICSI). Despite uniform fertilization rates (71 +/- 4%), progression of embryos to blastocysts varied when expressed as a monthly average, from 20 to 85%, with lows from February to April and again in October, which could be attributed to developmental failure of a significant number of oocyte cohorts (14 of 55). Blastocyst rates, after elimination of failed cohorts, were uniform over time (59 +/- 4%). Neither culture conditions, the number of follicular stimulations, nor the individual sperm or oocyte donor were associated specifically with developmental failure, suggesting that intrinsic differences between stimulation cycles account for the observed variation in developmental potential. The in-vivo developmental competence of ICSI-produced embryos grown to blastocysts in vitro was also assessed. Two ongoing pregnancies and the birth of a normal female, 'Blastulina', represent landmarks in efforts to expand the use of ART in the rhesus monkey.     

Cryopreservation of human and rabbit oocytes and one-cell embryos: a comparison of DMSO and propanediol

The aim of this study was to improve the cryopreservation ofhuman oocytes and pronuclear embryos. One-step and multiple-stepaddition of dimethyl sulphoxide (DMSO) and 1, 2-propanediol(PROH) and three different freezing protocols with intermediatetemperatures of –35, –70 and –110°C wereinvestigated. This work was performed using rabbit oocytes aswell as human oocytes and one-cell embryos from the routineIVF programme. Also, human polyploid pronucleate oocytes wereused in controlled prospective studies of morphological intactnessand development in vitro. Rabbit oocytes survived best (113/126)when PROH was added in one step and controlled freezing stoppedat –110°C. But the development was better (141/187)if DMSO was added in multiple steps and the oocytes were cooledto –70°C before being plunged into liquid nitrogen.The mode of addition of the cryoprotectant influenced developmentonly if slow freezing was stopped at –35°C (51 versus34%). Using PROH, the development after thawing was also betterif cooling was stopped at –35°C (51 versus 37%) andDMSO was superior to PROH when the oocytes were cooled slowlyto –110°C (66 versus 37%). In the human, significantlymore pronucleated than unfertilized oocytes developed afterfreezing (92 versus 50%). The best results were achieved withpronuclear embryos using 1.5 M PROH and cooling to –110°C,when 91.7% of the surviving oocytes developed further. Thisis a marked improvement of the development rate and comparableto embryo freezing     

Cryopreservation of metaphase II human oocytes effects mitochondrial membrane potential: implications for developmental competence

BACKGROUND: Current outcome results with embryos derived from thawed MII human oocyes are significantly lower than with embryos cryopreserved at the pronuclear stage. Here, we investigated whether freezing-thawing was associated with changes in oocyte mitochondrial polarity (DeltaPsim) that could influence competence by altering ATP levels or the ability of the cytoplasm to regulate intracellular Ca2+. METHODS: Fresh and thawed uninseminated and unfertilized MII oocytes were stained with the DeltaPsim-specific probe JC-1 to detect clusters of high-polarized mitochondria (J-aggregate positive) and with the Ca2+- specific probe Fluo-4 to measure changes in intracellular levels of this cation. ATP content per oocyte was measured directly and cortical granules were visualized with a cortical granule-specific probe. RESULTS: A significant difference between fresh and thawed MII oocytes existed for pericortical J-aggregate fluorescence and for the ability of the cytoplasm to increase free Ca2+ in response to ionophore exposure. No significant difference in ATP contents was measured and cryopreservation was not associated with an apparent release of cortical granules. CONCLUSION: Irreversible loss of high DeltaPsim in thawed oocytes may be associated with defects in Ca2+ signalling after insemination and could have downstream consequences for normal embryogenesis.     

Rescue ICSI of unfertilized oocytes after IVF

BACKGROUND: Failed fertilization after IVF occurs in 10-20% of cycles. Conflicting results of rescue fertilization by ICSI have been reported. We therefore compared the success rate in terms of fertilization and pregnancy of cycles in which rescue ICSI was performed with those from a matched control group of primarily ICSI cycles. METHODS: Unfertilized oocytes from IVF cycles with total fertilization failure where at least four metaphase II oocytes were available were treated by ICSI (group I; n = 120). A matched control group was established with patients undergoing ICSI during the same period (group II; n = 280). RESULTS: Both fertilization rate and the proportion of embryos with four blastomeres on day 2 after ICSI were significantly higher in the control group (P < 0.05). Embryo quality, however, was comparable in both groups. The pregnancy rate in the control group was 25.3% whereas in group I with rescue ICSI, no pregnancy was obtained. CONCLUSIONS: Although unfertilized oocytes after IVF can be fertilized by ICSI, the developmental potential of the ensuing embryos is very poor. Therefore, rescue ICSI after total failure of fertilization is not recommended.     

In-vitro matured metaphase-I oocytes have a lower fertilization rate but similar embryo quality as mature metaphase-II oocytes after intracytoplasmic sperm injection.

About 4% of all the oocytes denuded prior to intracytoplasmic sperm injection (ICSI) are in metaphase-I (MI). Frequently, these oocytes achieve meiosis after a few hours of in-vitro culture and are available for ICSI on the day of oocyte retrieval. In this retrospective study, the aim was to evaluate the fertilization rate and the developmental capacity of these in-vitro matured MI oocytes. After controlled ovarian stimulation using human menopausal gonadotrophin (HMG) and human chorionic gonadotrophin (HCG) in 896 ICSI cycles, 1210 MI-to-MII-matured oocytes were injected approximately 4 h after in-vitro culture and 8803 MII oocytes were injected immediately, or later, after denudation. The fertilization rate of in-vitro matured oocytes was significantly lower than that of mature MII oocytes (52.7 and 70.8% respectively, P < 0.00l). Embryo quality was only slightly different as regards the numbers of good quality embryos: 47.4% good quality embryos were obtained in the in-vitro matured oocyte group, whereas 53.2% good quality embryos were obtained in the MII oocyte group (P < 0.05). The same proportions of excellent (5.7 and 7.0%, NS) and fair quality (17.6 and 15.3%, NS) embryos were obtained for in-vitro matured and mature oocytes respectively. Embryos derived from in-vitro matured oocytes were transferred only if they were of better quality or if there were not enough mature oocyte derived embryos available. Fifteen transfers involved only embryos derived from in-vitro matured oocytes: 11 single embryo transfers and four transfers of two embryos, resulting in one singleton pregnancy and the birth of a healthy baby. It may be concluded that in cycles with few MII oocytes it might be worthwhile to inject in-vitro matured MI oocytes in order to increase the number of embryos available for transfer.     

Fertilization and early embryology: Cryopreservation of immature mouse oocytes

Mouse oocytes enclosed in cumulus cells were isolated from antralfollicles at the germinal vesicle (GV) stage. They were storedin straws at – 196°C by a conventional mouse embryofreezing method using dimethylsulphoxide (1.5 M) as the cryoprotectant.Overall survival assessed after removal of the cumulus cellswas 93% (299/320). A significantly greater proportion of freshoocytes remained arrested at the GV stage during culture (11versus 1%), but the rate of maturation to metaphase II was notsignificantly different between frozen and fresh oocytes (83versus 74%). The rate of fertilization in vitro was similarfor frozen and fresh oocytes matured in vitro (70 versus 81%)but significantly less than with mature ovulated oocytes (96%).Fertilization of frozen and fresh oocytes arrested after germinalvesicle breakdown was similar (77 versus 95%. No evidence ofparthenogenetic activation was found in the different groupsafter overnight incubation of metaphase II oocytes. Implantationwas similar for embryos derived from fresh and frozen GV-stageoocytes matured in vitro and mature ovulated oocytes, but theloss of embryos after implantation was significantly higherin the in-vitro matured groups (frozen, 40% and fresh, 46% versus24%). The overall survival of oocytes frozen at the GV stagewas 27%. This compares favourably with the estimated overallsurvival of mature oocytes cryopreserved by a similar procedure.We conclude that the increased post-implantation loss is dueto suboptimal conditions for maturation in vitro rather thanfreezing injury.     

High outcome predictability after IVF using a combined score for zygote and embryo morphology and growth rate

BACKGROUND: A scoring system has been developed to determine preimplantation embryo quality, and used to select embryos for transfer into the uterus of patients. METHODS AND RESULTS: The system was used to study early embryo development and to test whether these scores alone can accurately predict IVF outcome. Following zygote and embryo scores through early development, the data showed that a top quality zygote does not necessarily indicate that the resulting embryo will be top quality after in-vitro culture. The embryo quality score can change dramatically when embryos are cultured to day 2 or 3 post-fertilization. Pregnancy rates and implantation rates were compared with the cumulative and separated zygote and embryo scores. Analysis of the predictability of scoring systems suggested that morphological scores alone are relatively unpredictive of IVF outcome. When weighted for in-vitro growth rate, scores were highly predictive, more so than the rate of development alone. CONCLUSIONS: These data suggested that a combination of in-vitro growth rate and morphological analysis both of zygotes and embryos was highly indicative of outcome after IVF. The results can be adopted to the single embryo transfer approach to IVF.     

Cryopreservation of human embryos obtained after gamete intra-Fallopian transfer and/or in-vitro fertilization

During a one-year period 636 excess embryos obtained after in-vitrofertilization and gamete intra-Fallopian transfer combined within-vitro fertilization were cryopreserved using two differentprotocols. For early stage embryos including the pronucleatestage, 1,2-propanediol was used as cryoprotectant (procedureA, adapted from Renard) and for later stage embryos dimethylsulphoxidewas used in protocol B, adapted from Trounson and Mohr. Afterthawing 288 embryos, half of them were of sufficient qualityto be replaced. After cryopreservation, procedure A gave thebest survival in embryos having 2 blastomeres; for later stageembryos best survival was obtained using the dimethylsulphoxideprotocol. Survival after cryopreservation was also clearly relatedto the quality of the embryos prior to freezing. Embryos werereplaced during endocrinologically monitored natural cyclesand were transferred in synchrony between endornetrial and embryonicage. After replacement of 126 embryos in 110 patients, 20 pregnanciesoccurred. So far six healthy children have been born, two patientsaborted and 12 pregnancies are ongoing. In this series no statisticaldifference was observed between the implantation rate of embryoscryopreserved by procedure A or B. Six pregnancies occurredin patients from the oocyte and embryo donation programme. Anadequate cryopreservation programme circumvents the difficultproblem of synchronizing the ovarian cycles of donor and acceptorpatients.     

Day 2 elective single embryo transfer in clinical practice: better outcome in ICSI cycles

BACKGROUND: Single embryo transfer (SET) after IVF/ICSI has been shown to result in an acceptable pregnancy rate in selected subjects. In our unit, SET is routinely carried out among women under the age of 36 in the first or second treatment cycle when a top-quality embryo is available. In order to define further the selection criteria for SET, we have analysed the outcome of elective SET (eSET), including the cumulative pregnancy rate after frozen embryo transfers, performed in the years 2000-2002 in the Oulu Fertility Center. METHODS: During the study period, a total of 1271 transfers were performed, and in 468 cycles SET (39% of all transfers) was carried out. Of the SET cycles, in 308 cases a top-quality embryo was transferred on day 2 and extra embryos were frozen. Of these eSET cycles, ICSI was carried out in 87 cycles (28%). RESULTS: The overall clinical pregnancy rate per transfer was 34.7% in the eSET cycles. In the eSET ICSI cycles, the clinical pregnancy rate was significantly higher than in the corresponding IVF cycles (50.6 versus 28.5%, P < 0.001). The cumulative pregnancy rate per patient after fresh and frozen embryo transfers was also significantly higher after ICSI (71.2 versus 53.4%, P < 0.01). CONCLUSIONS: A high cumulative pregnancy rate per oocyte retrieval can be achieved after eSET in daily clinical practice. The implantation rate of fresh top-quality embryos in the ICSI cycles was significantly higher than in the IVF cycles, possibly due to more successful selection of the embryo for embryo transfer on day 2 after ICSI. In addition, our data suggest that embryo quality is a more important determinant of outcome than the age of the woman.     

'Vanishing embryo syndrome' in IVF/ICSI

BACKGROUND: In a Danish population-based cohort study assessing the risk of cerebral palsy in children born after IVF, we made some interesting observations regarding 'vanishing co-embryos'. METHODS and RESULTS: All live-born children born in Denmark from 1 January 1995 to 31 December 2000 were included in this analysis. The children conceived by IVF/ICSI (9444) were identified through the IVF Register, the children conceived without IVF/ICSI (395 025) were identified through The Danish Medical Birth Register. Main outcome measure was the incidence of cerebral palsy. Within the IVF/ICSI children we found indications of an increased risk of cerebral palsy in those children resulting from pregnancies, where the number of embryos transferred was higher than the number of children born. CONCLUSIONS: The association between vanishing embryo syndrome and incidence of cerebral palsy following IVF requires further investigation in larger, adequately powered, studies.     

IVF/ICSI twin pregnancies: risks and prevention

Since the 1970s, the national twin birth rates have been increasing worldwide. Apart from the increasing childbearing age, the main cause is the use of assisted reproductive technologies (ART). To explore the overall consequences of dual embryo transfer (DET), the literature has been reviewed systematically regarding short- and long-term outcomes of IVF/ICSI twin pregnancies i.e. pregnancy complications, maternal risks, obstetric outcome and long-term morbidity including neurological sequelae, cognitive development and family implications. Another consequence of DET is vanishing twins, which seems to be a possible cause of adverse outcome in IVF singletons. The sparse literature on vanishing twins in IVF pregnancies and the influence on the surviving co-twin were also addressed. Finally, to determine the effects of implementing elective single embryo transfer (eSET), trials concerning eSET versus DET were analysed. In the light of the steadily increasing twin birth rates and the findings in this overview, where IVF/ICSI twins carry adverse outcome, it should be emphasized that the major obstacle in IVF remains the high twin birth rate. Furthermore vanishing twins account for another hazard of DET. These problems can be resolved by implementing eSET, diminishing the twin birth rate without affecting the overall goal of achieving a healthy infant.     

Comparison of triple serum screening and pregnancy outcome in oocyte donation versus IVF pregnancies

The current study compared triple serum screening results and outcomes in 37 oocyte donation (OD) and 46 self oocyte IVF-conceived singletons of similarly aged women (28.8 +/- 4.4 years and 30.7 +/- 4.5 years respectively). Both groups were followed from their embryo transfer and throughout pregnancy. Although the daily pattern of first-trimester serum beta-human chorionic gonadotrophin (HCG) was similar in both groups, higher mid-gestation HCG serum concentrations were found, i.e. 1.38 and 1.32 multiples of the median (median MoM) for IVF and OD respectively, in comparison with 0.99 median MoM from the same reference laboratory. Only the OD group had significantly increased alpha fetoprotein (AFP) concentrations (1.45 median MoM) (P = 0.002) compared with the reference laboratory. A total of 11% of the IVF and 13% of the OD women were found to be screen positive. In neither group were chromosomal abnormalities detected and no fetal or neonatal deaths were recorded. Seven (15%) of the OD and seven (19%) of the IVF women had an adverse obstetric outcome. Of those cases, six IVF and four OD women had serum HCG > or = 1.2 MoM and five OD women had AFP >1.2 MoM. Therefore, in those pregnancies the high serum HCG concentrations may alert for adverse obstetric outcome rather than indicating a high risk for Down's syndrome fetuses.     

Early cleavage of human embryos: an effective method for predicting successful IVF/ICSI outcome.

BACKGROUND: The need for effective parameters for selecting the best embryos is paramount when a large number of them are available for transfer. Other studies have reported that transfer of pre-selected embryos, based on cleavage to the 2-cell stage at 25 h and 27 h post-insemination/intracytoplasmic sperm injection (ICSI), increases implantation and pregnancy rates. We investigated whether extending the time for selection of cleaved embryos to 29 h post-insemination/ICSI had a similar effect on pregnancy and implantation rates. METHODS: Cleavage to the 2-cell stage was assessed at 25, 27 and 29 h post-insemination/ICSI. Embryos that had cleaved at any of these time points were designated as 'early cleavage' (EC), while others were designated as 'non-early cleavage' (NEC). EC embryos were selected and preferentially transferred. RESULTS: EC occurred in 57% of the cycles (61% IVF; 51% ICSI). Significantly (P = 0.02) more clinical pregnancies occurred in the EC group (23/42, 55%) compared with the group that had no embryo undergoing first cleavage up to 29 h post-insemination/ICSI (8/32, 25%). The EC group of patients was significantly younger than the NEC. CONCLUSION: Transfer of selected embryos that reached the 2-cell stage between 25 and 29 h post-insemination/ICSI is a reliable prognostic tool for patients undergoing assisted reproduction techniques.     

Number of embryos for transfer after IVF and ICSI: a Cochrane review

BACKGROUND: The most common complication of IVF is multiple pregnancy, which occurs in 25% of pregnancies following the transfer of two embryos. Single embryo transfer can minimize twin pregnancies but could also lower live birth rates. Our aim was to perform a systematic review of randomized trials to determine the effectiveness of single versus double embryo transfer. METHODS: Cochrane Collaboration review methods were followed. Randomized controlled trials comparing single and double embryo transfers were identified by searching Medline, EMBASE and the Cochrane register of controlled trials. Contents of specialist journals and proceedings from meetings of relevant societies were hand searched. Data were pooled with Rev Man software using the Peto-modified Mantel-Hanzel method. RESULTS: Pooled results from four trials indicate that although double embryo transfer leads to a higher live birth rate per woman [odds ratio (OR) 1.94, 95% confidence interval (CI) 1.47-2.55] in a fresh IVF cycle, comparable results are obtained by subsequent transfer of a frozen embryo (OR 1.19, 95% CI 0.87-1.62). The multiple pregnancy rate is significantly higher (OR 62.83, 95% CI 8.52-463.57) after double embryo transfer. CONCLUSIONS: Single embryo transfer significantly reduces the risk of multiple pregnancy, but also decreases the chance of live birth in a fresh IVF cycle. Subsequent replacement of a single frozen embryo achieves a live birth rate comparable with double embryo transfer.     

Fertilization of human oocytes following cryopreservation; normal karyotypes and absence of stray chromosomes

Survival following cryopreservation of fresh and aged humanoocytes by the propanediol (PROH) procedure was observed in51 and 73% of oocytes respectively, immediately after thawing.This survival was reduced in both types of oocytes at the timeof insemination (3–4h) to 41% in fresh and 61% in agedoocytes. Insemination of the cryopreserved and control oocyteswith spermatozoa from one donor resulted in total fertilizationrates similar to our in-vitro fertilization (IVF) rate for non-malefactor patients. The normal fertilization rate for fresh cryopreservedoocytes was slightly lower (46%) than the rate for IVF oocytes(59%) (P<0.05), while the abnormal fertilization rates werenot significantly different (16 and 15% respectively). In contrast,a reduction in the normal fertilization rate was observed forthe aged cryopreserved oocytes (13%) compared to the IVF rate(P< 0.001). Associated with this was an increase in the abnormalfertilization rate for the aged cryopreserved oocytes, whichwas significantly higher (47%) than the IVF rate (15%) (P<0.001). Significant differences in the total and normal fertilizationrates were observed between cryopreserved oocytes obtained fromcohorts with 27 (total: 84%, normal: 68%) and >27 oocytes(total: 55%, normal: 33%) (P< 0.05). Fertilized oocytes andoocytes with abnormal or absent spindles were examined for chromosomalloss and no stray chromosomes were observed in any of thesecryopreserved oocytes (n =; 137). In the cryopreserved oocyteswhich had undergone normal fertilization, four scorable karyotypeswere achieved and in all of these two sets of 23 chromosomeswere observed.     

Cryopreservation of human oocytes and fertilization by two techniques: in-vitro fertilization and intracytoplasmic sperm injection

Human oocyte cryopreservation results in poor survival and subsequentfertilization rates. It has been suggested that freeze-thaw-inducedchanges in the zona pellucida may impair sperm penetration orattachment. The aim of this study was to compare fertilizationand cleavage rates in cryopreserved oocytes inseminated by conventionalin-vitro fertilization (IVF) or intracytoplasmic sperm injection(ICSI). A total of 220 oocytes, obtained from volunteers whohad undergone ovarian stimulation, were cryopreserved usinga slow freeze-rapid thaw protocol with 1.5 M propanediol asthe cryoprotectant. Surviving oocytes (n= 74, 34.4%) were randomlyallocated for fertilization by conventional IVF (group 1) orICSI (group 2) using cryopreserved spermatozoa from a singledonor of proven fertility. Fertilization was achieved in five(13.5%) of the oocytes in group 1 and 17 (45.9%) in group 2(P < 0.005), with only one oocyte in group 1 exhibiting normalfertilization as opposed to 16 (43.2%) in group 2 (P < 0.001).Similarly, one oocyte fertilized by IVF cleaved, while all fertilizedwith ICSI cleaved (P < 0.001). We conclude that althoughthe survival of oocytes is poor following cryopreservation,fertilization and cleavage rates can be enhanced significantlyusing ICSI. These data also suggest that the method of cryopreservationused in this study affected the zona pellucida, such that normalsperm attachment or penetration was impaired.