Development and integration of an extended embryo culture program

Cleavage stage versus blastocyst stage embryo transfer in assisted conception

BACKGROUND

Recent advances in cell culture media have led to a shift in IVF practice from early cleavage embryo transfer to blastocyst stage transfer. The rationale for blastocyst culture is to improve both uterine and embryonic synchronicity and self selection of viable embryos thus resulting in higher implantation rates.

OBJECTIVES

To determine if blastocyst stage embryo transfers (ETs) affect live birth rate and associated outcomes compared with cleavage stage ETs and to investigate what factors may influence this.

SEARCH STRATEGY

Cochrane Menstrual Disorders and Subfertility Group Specialised Register of controlled trials, Cochrane Controlled Trials Register (CENTRAL) (The Cochrane Library), MEDLINE, EMBASE and Bio extracts. The last search date was January 2007.

SELECTION CRITERIA

Trials were included if they were randomised and compared the effectiveness of early cleavage versus blastocyst stage transfers.

DATA COLLECTION AND ANALYSIS

Of the 50 trials that were identified, 18 randomised controlled trials (RCTs) met the inclusion criteria and were reviewed. The primary outcome was rate of live birth. Secondary outcomes were rates per couple of clinical pregnancy, multiple pregnancy, high order pregnancy, miscarriage, failure to transfer embryos and cryopreservation. Quality assessment, data extraction and meta-analysis were performed following Cochrane guidelines.

MAIN RESULTS

Evidence of a significant difference in live-birth rate per couple between the two treatment groups was detected in favour of blastocyst culture (9 RCTs; OR 1.35, 95% CI 1.05 to 1.74 (Day 2/3: 29.4% versus Day 5/6: 36.0%)). This was particularly for trials with good prognosis patients, equal number of embryos transferred (including single embryo transfer) and those in which the randomisation took place on Day 3. Rates of embryo freezing per couple was significantly higher in Day 2 to 3 transfers (9 RCTs; OR 0.45, 95% CI 0.36 to 0.56). Failure to transfer any embryos per couple was significantly higher in the Day 5 to 6 group (16 RCTs; OR 2.85, 95% CI 1.97 to 4.11 (Day 2/3: 2.8% versus Day 5/6: 8.9%)) but was not significantly different for good prognosis patients (9 RCTs; OR 1.50, 95% CI 0.79 to 2.84).

AUTHORS' CONCLUSIONS

This review provides evidence that there is a significant difference in pregnancy and live birth rates in favour of blastocyst transfer with good prognosis patients with high numbers of eight-cell embryos on Day three being the most favoured in subgroup for whom there is no difference in cycle cancellation. There is emerging evidence to suggest that in selected patients, blastocyst culture maybe applicable for single embryo transfer.

Insulin and insulin-like growth factor stimulation of vascular endothelial growth factor production by luteinized granulosa cells: comparison between polycystic ovarian syndrome (PCOS) and non-PCOS women

CONTEXT

Vascular endothelial growth factor A (VEGF-A) is a potent cytokine that promotes angiogenesis and vascular permeability. After controlled ovarian stimulation (COS) for in vitro fertilization (IVF), excessive VEGF-A production can occur, particularly in women with polycystic ovarian syndrome (PCOS); however, it is unclear whether the regulation of VEGF-A production is different between PCOS and non-PCOS women.

OBJECTIVE

The aim of this study was to determine whether there were differences in the dose- and time-dependent effects of insulin and IGFs on VEGF-A production by luteinized granulosa cells (LGCs) from women with and without PCOS.

DESIGN AND SETTING

A prospective comparative experimental study was conducted at an institutional practice.

PATIENTS

Patients included six PCOS and six non-PCOS women undergoing COS and IVF.

INTERVENTIONS

Interventions included COS for IVF.

MAIN OUTCOME MEASURES

VEGF-A levels in culture media were collected daily for 3 d from LGCs after incubation with variable doses of insulin, IGF-I, and IGF-II in the presence and absence of LH.

RESULTS

In both study groups, exposure to LH alone did not alter VEGF-A levels. However, insulin or IGF increased VEGF-A levels within 1 d and appeared to synergize with LH at 3 d. VEGF-A production by non-PCOS LGCs was more sensitive to IGF exposure, whereas PCOS cells were more sensitive to insulin. Although an increase in DNA content (P < 0.05) was noted in cultures of PCOS cells, progesterone levels were lower compared with non-PCOS LGCs.

CONCLUSION

Insulin and IGFs promote VEGF-A production in LGCs, but the response patterns are different when cells from PCOS and non-PCOS women are compared.

Successful pregnancy rates achieved with day 4 embryo transfers

OBJECTIVE

To assess the success of day 4 embryo transfers (ETs) following IVF at one institution.

DESIGN

Retrospective analysis.

SETTING

A university hospital IVF program.

PATIENT(S)

Two hundred nondonor, fresh IVF cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE

Outcomes of IVF. Outcome assessments after day 4 ETs included rates of implantation, clinical pregnancy, and singleton and multiple live births.

RESULT(S)

The overall live-birth rate was 54.4%. Implantation rates were highest in younger age groups, and similar in patients 35-40 years of age. Pregnancy and live-birth rates were similar across all age groups up to age 40 years. Multiple gestations were highest in women < or =40 years of age.

CONCLUSION

Acceptable pregnancy rates can be achieved with day 4 ETs.

Cleavage stage versus blastocyst stage embryo transfer in assisted conception

BACKGROUND

In the past decade, advances in the understanding of nutrient requirements of embryos, has led to the evolution of culture media designed to support extended culture of embryos in vitro from the standard procedure of 2 to 3 days (for early cleavage embryo transfer) to 5 to 6 days (blastocyst culture). The rationale for blastocyst culture is to improve the synchronicity of uterine and embryonic development and provide a mechanism for self-selection of viable embryos. Since the initial widespread introduction of blastocyst culture in 1998, there has been conflicting reports about the clinical benefits of this technique.

OBJECTIVES

To determine if blastocyst stage embryo transfers (ETs) affects success rates compared with cleavage stage ETs and investigate what factors may influence this.

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group Specialised Register of controlled trials. We also searched the Cochrane Controlled Trials Register (CENTRAL) (The Cochrane Library), MEDLINE, EMBASE and Bio extracts. Attempts were made to identify trials from the National Research Register, the Clinical Trials Register and the citation lists of review articles and included trials. The last search date was May 2005. The first or corresponding author of each included trial was contacted for additional information.

SELECTION CRITERIA

Trials were included if they were randomised and compared the effectiveness of early cleavage versus blastocyst stage transfers.

DATA COLLECTION AND ANALYSIS

Of the 45 trials that were identified, 16 trials met the inclusion criteria and were reviewed. Primary outcomes were rates of live birth, clinical pregnancy and multiple-pregnancy rates per couple. Secondary outcomes were rates of miscarriage, failure to transfer embryos, freezing, implantation and high order pregnancy and per cycle data. Quality assessment and data extraction were performed independently by two review authors. Meta-analysis was performed using odds ratios (OR) for dichotomous outcomes and weighted mean differences for binary outcomes with 95% confidence intervals (CI).

MAIN RESULTS

There was no evidence of a difference in live-birth rate per couple between the two treatment groups (7 RCTs; OR 1.16, 95% CI 0.74 to 1.44 [Day 2/3 34.3% vs. Day 5/6 35.4%]); in the clinical pregnancy rate per couple (15 RCTs; OR 1.05, 95% CI 0.88 to 1.26 [Day 2/3 38.8% vs. 40.3%]) even for good prognosis patients (6 RCTs: OR 96% 1.06 CI 0.83 to 1.34). There was also no difference in multiple-pregnancy rate per couple (12 RCTs; OR 0.85, 95% CI 0.63 to 1.13) particularly in trials where equal numbers of embryos were transferred in both groups (6 RCTs: OR 0.91, 95% CI 0.63 to 1.32). There was no evidence of a difference in high order multiple-pregnancy rates per couple (5 RCTs; OR 0.44, 95% CI 0.15 to 1.33) or miscarriage rate per couple between the two groups (9 RCTs; OR 1.33, 95% CI 0.89 to 2.01). Rates of embryo freezing per couple was significantly higher in Day 2 to 3 transfers (9 RCTs; OR 0.45, 95% CI 0.36 to 0.57). Failure to transfer any embryos per couple was significantly higher in the Day 5 to 6 group (10 RCTs: OR 3.21, 95% CI 2.15 to 4.81[Day 2/3 3.5% vs D 5/6 10.1%]), but was not significantly different for good prognosis patients (7RCTs, OR 1.58 95% CI 0.65 to 3.82).

AUTHORS' CONCLUSIONS

There is no evidence of a difference in live birth or pregnancy outcomes between Day 2 to 3 and Day 5 to 6 transfer of embryos. Blastocyst transfer was associated with an increase in failure to transfer any embryos in a cycle and a decrease in embryo freezing rates. In the absence of data on cumulative live birth rates resulting from fresh and thawed cycles, it is not possible to determine if this represents an advantage or disadvantage.

The role for preimplantation genetic diagnosis in balanced translocation carriers

OBJECTIVE

Preimplantation genetic diagnosis is an established technique that provides an alternative to prenatal diagnosis for patients who are at risk of transmitting a serious genetic disorder to their offspring. Preimplantation genetic diagnosis has been used for couples who have been at risk for having offspring with single gene or X-linked disorders and for screening for common age-related aneuploidy and in couples who themselves carry balanced chromosomal rearrangements. The aim of this study was to summarize our experience using preimplantation genetic diagnosis after the identification of a parental balanced translocation, specifically as it relates to the number of embryos that are suitable for transfer after preimplantation genetic diagnosis for a known translocation and aneuploidy screening.

STUDY DESIGN

This is a retrospective review of data from a single center that involved 6 couples that initiated the process of preimplantation genetic diagnosis for translocation and aneuploidy screening by fluorescent in situ hybridization.

RESULTS

A total of 65 embryos were obtained, of which 56 embryos (86%) were suitable for fluorescent in situ hybridization analysis. After fluorescent in situ hybridization, 1 embryo was diagnosed as normal or balanced (1.7%). Forty-three embryos (76.8%) were unbalanced for the translocation; 8 embryos (14.3%) were aneuploid, and 4 embryos (7.1%) were uninformative. There were no clinical pregnancies.

CONCLUSION

In our experience, there are very few embryos that are available for transfer from these patients after translocation and aneuploidy screening because of multiple unbalanced segregation products and a high rate of aneuploidy. Factors that contributed to this may be related to which parent carries the translocation, methods that were used for in vitro fertilization, and advanced maternal age. Although preimplantation genetic diagnosis for translocation carriers theoretically can enhance the pregnancy rate for a couple, there are limitations. This information should be shared with couples who are contemplating preimplantation genetic diagnosis for translocation, and the options of sperm or egg donor should be considered.

Clinical experience and perinatal outcome of blastocyst transfer after coculture of human embryos with human endometrial epithelial cells: a 5-year follow-up study

OBJECTIVE

To evaluate the reproductive and neonatal outcome of blastocyst transfer after coculture with human endometrial epithelial cells in IVF and oocyte donation.

DESIGN

Retrospective study. Private assisted reproductive center.

PATIENTS(S)

Two hundred sixty women undergoing IVF and 469 oocyte recipients.

INTERVENTION(S)

IVF or intracytoplasmic sperm injection (ICSI) and transfer of at least one blastocyst after coculture with human endometrial epithelial cells.

MAIN OUTCOME MEASURE(S)

Blastocyst formation rate, implantation and pregnancy rates, neonatal outcome, and congenital birth defects.

RESULT(S)

Among patients who had transfer with their own oocytes, 1193 of 2349 cocultured embryos developed up to the blastocyst stage (50.8%), and pregnancy and implantation rates of 33.9% and 19.2%, respectively, were achieved. In the oocyte donation program, 1819 blastocysts were obtained from 3127 embryos (58.2%), with subsequent pregnancy and implantation rates of 57.0% and 31.0%, respectively. The blastocyst rate remained stable throughout the 5 years of the study, but the pregnancy and implantation rates increased dramatically. Of 139 deliveries, 57 (41.0%) were multiple pregnancies and 1 (0.7%) was a multifetal birth (four live born infants). Out of 200 children born, 59% were male, and congenital birth defects were observed in 2.5%.

CONCLUSION(S)

Coculture of human embryos with endometrial epithelial cells yields a blastocyst formation rate of 50.8% to 58.2% and encouraging implantation and pregnancy rates. This technique reduces the mean number of embryos transferred in each patient. The number of embryos implanted is more relevant to neonatal outcome than is the coculture system and blastocyst transfer used. The risk of congenital birth defects associated with this program is similar to that recorded in early ET in IVF or ICSI.

Pregnancy outcomes using donor sperm insemination after failed in vitro fertilization with intracytoplasmic sperm injection cycles in couples with complex infertility disorders

OBJECTIVE

To evaluate alternatives for couples with severe male factor infertility who fail to conceive with IVF-intracytoplasmic sperm injection (ICSI).

DESIGN

Outcomes of couples using artificial insemination with donor sperm (AID) after failed IVF-ICSI, assessing multiple risk factors affecting prognosis.

SETTING

University infertility service.

PATIENT(S)

Nineteen patients with complex infertility disorders who failed IVF-ICSI and subsequently used AID (1 to 7 cycles).

INTERVENTION(S)

Artificial insemination with donor sperm was performed 36 hours after detection of an LH surge or hCG injection.

MAIN OUTCOME MEASURE(S)

Pregnancy outcomes were determined.

RESULT(S)

Seventeen pregnancies occurred in 16 women associated with AID for a pregnancy rate per cycle of 27.9% within a mean of 3.2 +/- 18 cycles. Live birth rate per cycle was 24.6%.

CONCLUSION(S)

A high pregnancy rate was achieved with AID in women who failed IVF-ICSI. Given the low cost and effectiveness of AID in this series, consideration of AID is a reasonable and effective option even in couples with poor prognosis who fail to conceive with IVF-ICSI.

Effect of ICSI on subsequent blastocyst development and pregnancy rates

PURPOSE

To investigate whether ICSI (intracytoplasmic sperm injection) results in decreased blastocyst formation and pregnancy compared to IVF (in vitro fertilization).

METHODS

We performed a retrospective analysis of blastocyst transfer (BT) offered routinely to patients under age 40 with > or = three 8-cell embryos on day 3 and compared IVF to ICSI cycles. Sequential media were used with P1 until day 3, then Blastocyst Medium until day 5/6.

RESULTS

There were 131 IVF and 75 ICSI cycles. There was no difference in age, number of oocytes, zygotes, 8-cell embryos, blastocysts on days 5 and 6, or embryos transferred. Progression to blastocyst was similar (78% for IVF and 73% for ICSI) as was the viable pregnancy rate (51.4% for IVF and 55% for ICSI). No cycles failed to form blastocysts.

CONCLUSIONS

The progression to blastocyst and the likelihood of conceiving a viable pregnancy were unaltered by ICSI. Thus it seems appropriate for programs to offer BT to patients undergoing ICSI using the same inclusion criteria applied to their IVF patients.

High rate of mixoploidy among human blastocysts cultured in vitro

OBJECTIVE

To determine the incidence and type of mixoploidy in human blastocysts produced in vitro.

DESIGN

A laboratory study of spare blastocysts from an IVF program.

SETTING

University hospital laboratory.

PATIENT(S)

Thirty-nine couples undergoing IVF or intracytoplasmic sperm injection.

INTERVENTION(S)

A total of 103 blastocysts were classified as good- or poor-quality blastocysts based on morphology. A total of 6,927 interphase nuclei, 5,015 from 59 good-quality and 1,912 from 44 poor-quality blastocysts, were assessed for ploidy by fluorescence in situ hybridization with chromosome-specific DNA probes.

MAIN OUTCOME MEASURE(S)

The percentage and the type of polyploid cells present in each blastocyst.

RESULT(S)

Mixoploidy (mixture of diploid and polyploid cells) was found in 86% of good-quality and 82% of poor-quality blastocysts analyzed. The type of polyploidy ranged from 3N to 14N, with tetraploidy being the most common between both groups. The proportion of polyploid cells per mixoploid blastocyst ranged from 1% to 88%. The percentage of polyploid nuclei within most good-quality mixoploid blastocysts was small (10%) and significantly lower than in poor-quality blastocysts (19%).

CONCLUSION(S)

Most human blastocysts produced in vitro contain polyploid, predominantly tetraploid cells. The proportion of polyploid cells in the majority of good-quality blastocysts is low. The small numbers of blastocysts with a high percentage of polyploid cells may have implications for blastocyst transfer.

Blastocyst culture: facts and fiction

The use of sequential media has made extended culture and transfer of blastocysts feasible for human IVF. Embryo transfer on day 5 has been claimed to result in higher implantation rates than transfer on day 3, on the basis of retrospective comparative studies. This is not supported convincingly, however, in randomized controlled trials published to date. Blastocyst culture imposes additional requirements in terms of personnel, equipment, education and cost and is associated with a greater incidence of monozygotic twinning and cycle cancellation rate than in the case of day 3 culture. In order for day 5 transfer to replace day 3 transfer, a convincing comparison between the two methods should therefore demonstrate the superiority of blastocyst transfer. There is still a need for properly designed randomized controlled trials to compare day 3 with day 5 transfer which will also address the effectiveness of a single blastocyst replacement in reducing the incidence of multiple pregnancies as well as the value of blastocyst cryopreservation.

Blastocyst culture in human IVF: the final destination or a stop along the way?

In the field of human IVF, culturing embryos to the blastocyst stage has gained popularity within the past few years. The impetus to transfer blastocysts has been spurred by several factors: 1) the desire to improve implantation rates in infertility patients, 2) a desire to reduce the multiple pregnancy rate by transferring fewer embryos, 3) the desire to perform pre-implantation genetic diagnosis, and 4) the advent of sequential media. Although culturing human embryos to the Hastocyst stage has improved implantation rates and reduced the incidence of multiple pregnancies in some patient populations, it has not worked for all populations of infertility patients. Factors that may affect the ability of a human embryo to reach the blastocyst stage include the patient's age, cohort of ova retrieved, the use of intracytoplasmic sperm injection of blastomere biopsy, culture conditions, or intrinsic factors within the embryo itself. Culture of human embryos to the blastocyst stage can be an effective method for improving implantation rates and reducing the high order multiple pregnancy rates seen in human IVF clinics when more than three embryos are transferred.

Multiple gestations in assisted reproductive technology: can they be avoided with blastocyst transfers?

OBJECTIVE

Blastocysts are advanced-stage embryos with high implantation potential; theoretically, limited numbers of blastocysts can be used for embryo transfer to achieve good pregnancy rates with low multiple pregnancy rates. Clinical outcomes of a newly implemented blastocyst transfer program were evaluated.

STUDY DESIGN

This study is a retrospective analysis of 553 blastocyst transfer cycles performed by a university-based in vitro fertilization program; risk factors associated with multiple gestations were analyzed.

RESULTS

An average of 2.2 embryos were used for embryo transfer. The overall clinical pregnancy rate per embryo transfer was 45.1%; multiple gestation, twin, and triplet rates were 40.9%, 36.5%, and 4.3%, respectively. Multiple gestations increased significantly (1) when embryo transfer was done on day 5, (2) when > or =2 blastocysts were present on day 5, and (3) when maternal age was < or =30 years.

CONCLUSION

In spite of a conservative approach to the number of blastocysts used for embryo transfer, the overall multiple pregnancy rate was high, and triplet pregnancies did occur.

Blastocyst transfer: does it really affect the outcome?

Blastocyst transfer is of great interest to most assisted reproductive technology clinics. The ability to select the best embryos to transfer in order to increase pregnancy rates, and to replace lower numbers of embryos to reduce the likelihood of an unwanted multiple pregnancy have both been realized. The optimal method to prolong embryo culture up to day 5 or 6 is still to be identified, although present techniques offer acceptable blastocyst development rates. Freezing of supernumerary blastocysts is still a matter of discussion, as adequate results are still awaited.

Alternative embryo transfer on day 3 or day 5 for reducing the risk of multiple gestations

PURPOSE

This study was carried out to reduce the possibility of high-order multiple gestations and the failure of embryo transfer by determining their replacement date based on the number and quality of 2-day embryos.

METHODS

All zygotes were cocultured with cumulus cells in 10 microliters of YS medium containing 10% human follicular fluid (hFF) for 48 or 96 hr. In period I, all embryos were transferred on day 3 (1032 cycles). In period II, the embryos were transferred on either day 3 or day 5 by determining their replacement date based on the number and quality of 2-day embryos: there were 2701 patients in whom embryos were replaced on day 3 (in the case that the number of zygotes was less than eight and the number of good-quality embryos was less than three) and 1952 patients less than 40 years old in whom embryos were replaced on day 5 (in the case that the number of zygotes was eight or more and/or the number of good-quality embryos was three or more). On the other hand, patients who were 40 years old or more were alloted to day 3 transfer cycles, regardless of the number and quality of the 2-day embryos, due to the possibility of their not producing blastocyst-stage embryos in vitro.

RESULTS

The number of embryos transferred in period II was 2.9 +/- 0.6, while that in period I was 3.7 +/- 0.5. The multiple pregnancy rate was significantly decreased in period II (30.7%) compared to that (49.6%) in period I, while the pregnancy and implantation rates in period II (36.1 and 16.4%, respectively) were not lower than those (34.9 and 16.1%, respectively) in period I. The rate of triplet or more gestations was significantly minimized in period II (2.3%) compared to that in period I (26.5%).

CONCLUSIONS

We propose that determination of the date on which embryos should be transferred based on the number and quality of embryos on day 2 may help to maintain an acceptable pregnancy rate, while minimizing embryo transfer failure and high-order multiple gestations.

Extended embryo culture in human assisted reproduction treatments

In order to evaluate the niche of extended embryo culture in an IVF programme, retrospective analysis of non-selected IVF patients, who underwent ovarian stimulation from April 1998 to June 1999 in a single private practice assisted reproductive technology centre, was performed. Embryos were cultured for 48 h in S1/G1.2 medium followed by 48 to 72 h of culture in S2/G2.2 to day 5 or day 6. Only fertilized oocytes exhibiting two pronuclei from donor and non-donor IVF and intracytoplasmic sperm injection (ICSI) cases were examined to determine the relationship between embryo cell number on day 3 and subsequent rate of blastocyst formation. Results indicated that a proportional relationship existed between the number of blastomeres present in day 3 embryos and the rate of blastocyst formation. Fifty-four per cent of embryos that had six cells on day 3 formed blastocysts, while 76% of those embryos with eight cells formed blastocysts. Blastocyst development did not increase further when embryos had more than eight cells on day 3, indicating that embryos with greater cell numbers on day 3 are not always predictive of a greater likelihood of blastocyst formation. Fertilized oocytes exhibiting two pronuclei from donors produced significantly more blastocysts (67%) than those from IVF patients (52%; P < 0.01), and had a significantly higher implantation rate (54%) compared with IVF patients (30%; P < 0.01). Furthermore, blastocyst cryopreservation resulted in significantly higher implantation rates than cryopreserved cleavage stage embryos (P < 0.001).

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.

Avoiding multiple pregnancies in ART: a plea for single embryo transfer

It has been generally accepted that triplets after IVF/intracytoplasmic sperm injection (ICSI) can and should be avoided by adopting a standard strategy of replacing no more than two embryos. However, there is an increasing awareness of the risks and costs and of the epidemic size of twin pregnancies after IVF/ICSI. This has resulted in efforts to replace no more than one embryo. However, this approach has been hampered by our relative inability to identify embryos with a very high implantation potential. To identify such embryos, a number of strategies are being considered, both at the two pronuclear (2PN), early cleavage and the blastocyst stages. At the 2PN stage, the polarity characteristics of the nucleoli have been shown to be correlated with a high implantation rate. Similarly, the morphological characteristics at day 2 and 3 have been used to describe top quality embryos in approximately 75% of all IVF/ICSI cycles. Blastocyst culture has resulted in very high implantation rates in the hands of some authors. No approach has shown its superiority at present, but initial experience with single embryo transfer (SET) at the early cleavage stage by Scandinavian and Belgian groups shows that an ongoing pregnancy rate of 35% and more can be achieved. Proper identification of patients at risk of a twin pregnancy after double embryo transfer is equally important. It is clear that mainly young patients (aged <34 years) during their first, perhaps first two, IVF/ICSI cycles constitute the main population at risk (responsible for >80% of all twins) and are the main target group for twin prevention by SET of a top quality embryo at whatever stage. Therefore, in our opinion, although a further fine-tuning of both embryo and patient characteristics relating to a high risk for (twin) pregnancy is desirable, SET should be introduced carefully and progressively in each IVF/ICSI programme from now on. Correct counselling is very important and both public and private insurers will have to join in the discussion.

Blastocyst culture and transfer increases the efficiency of oocyte donation

OBJECTIVE

To determine the impact of blastocyst transfer on an oocyte donation program.

DESIGN

Retrospective review of embryo transfer in an IVF clinic.

SETTING

Private assisted reproductive technology unit.

PATIENT(S)

Two hundred and twenty nine patients undergoing oocyte donation.

INTERVENTION(S)

Culture of pronucleate embryos to either day 3 or day 5 followed by embryo transfer.

MAIN OUTCOME MEASURE(S)

Implantation rates, pregnancy rates, and multiple gestations were analyzed.

RESULT(S)

Implantation rates and pregnancy rates were significantly increased by moving to extended embryo culture and transfer on day 5. After day 3 transfers, implantation and pregnancy rates were 47.1% and 75%, respectively. In contrast, on day 5 these rates were increased to 65.8% and 87.6%. Concomitantly, there were significantly fewer embryos transferred on day 5 (2.1) compared to day 3 (3.2).

CONCLUSION(S)

Blastocyst transfer is a highly effective treatment for patients who receive donor oocytes, allowing excellent pregnancy rates while significantly reducing the incidence of high-order multiple gestations.