A prospective randomized study: day 2 versus day 5 embryo transfer

BACKGROUND: This randomized controlled study was performed in an unselected IVF/ICSI population to test the hypothesis that blastocyst transfers result in higher clinical pregnancy rates (CPR) per oocyte retrieval when compared with day 2 transfers. METHODS: Blind randomization for transfer on day 2 (group 1) or day 5/6 (group 2) was performed before stimulation. Oocytes and embryos were cultured in sequential media in 5.5% CO(2), 5% O(2), 89.5% N(2) and 90% humidity. A maximum of two embryos was transferred. RESULTS: The two groups were similar for age, IVF indication, number of treatment cycles, rate of ICSI/IVF, number of fertilized oocytes and number of embryos transferred. The CPR/oocyte retrieval was comparable in group 1 (32%) and in group 2 (44%), while the CPR/embryo transfer was significantly higher (P < 0.01) in group 2 (60%) than in group 1 (35%). Similarly, the implantation rate per embryo transferred was significantly higher (P < 0.03) in group 2 (46%) than in group 1 (29%). The cryo-augmented delivery rate/oocyte retrieval was comparable in group 2 (36.3%) and in group 1 (28.6%). CONCLUSION: This randomized study in an unselected population showed a significantly higher CPR/embryo transfer and a tendency toward a higher CPR/oocyte retrieval in patients receiving blastocysts when compared with day 2 transfers.     

Ultrasound-guided embryo transfer maximizes the IVF results on day 3 and day 4 embryo transfer but has no impact on day 5

BACKGROUND: The use of ultrasound-guided embryo transfer has been reported to affect success rates in some centres but not others. In a prospective study, we examined the influence of ultrasound guidance in embryo transfer performed on different days after oocyte retrieval. METHODS: Two different methods of embryo transfer were evaluated in 1069 consecutive transfers. The ultrasound-guided embryo transfer was used in 433 cases, whereas 636 embryo transfers were performed with the tactile assessment ('clinical feel') method. RESULTS: Ultrasound-guided embryo transfer yielded a higher overall pregnancy rate than the 'clinical feel' approach, 47 versus 36% (P < 0.001). This difference was statistically significant where embryos were transferred after 3 or 4 days of culture, 45.9 versus 37.1% (P = 0.001) and 42.3 versus 27% (P = 0.035) respectively but not significant (P = 0.112) on day 5 embryo transfer (56.3 versus 45.7%). Likewise, the implantation rate was significantly different between the two groups on day 3 and 4 embryo transfer, 23.3 versus 15.8% (P < 0.01) and 21.6 versus 15.7% (P < 0.05%) respectively but no statistical difference was noted on day 5 embryo transfer, 26.7 versus 23.6%. CONCLUSION: Ultrasound assistance in embryo transfer on day 3 and 4 significantly improved pregnancy rates in IVF but had no impact on day 5.     

A prospective, randomized study: day 3 versus hatching blastocyst stage

BACKGROUND: Recently, advances in human IVF-embryo transfer (ET) have been reported using sequential media and blastocyst stage ET. In our previous report, using a prospective, randomized study, no advantage was found using the blastocyst stage ET compared with day 3 ET. This study was performed in order to evaluate implantation and pregnancy rates of hatching blastocyst stage ET compared with conventional day 3 ET. METHODS AND RESULTS: A total of 480 patient cycles were evaluated using a prospective, randomized study. The pregnancy rate and implantation rate were compared between the day 3 ET (n = 240) and hatching blastocyst stage ET (Hat ET; n = 240). The Hat ET group had a pregnancy rate of 29.3% (55 out of 188) and an implantation rate of 21.4% (67 out of 313). The day 3 ET group had a pregnancy rate of 29.2% (70 out of 240) and an implantation rate of 19.1% (93 out of 488). In the Hat ET group, the pregnancy rate, implantation rate and ongoing pregnancy rate of day 5 ET and day 6 ET were all higher than the respective rates in the day 7-9 ET group. CONCLUSION: We found that the pregnancy rate and implantation rate of ET with hatching stage blastocysts had no advantage compared with the conventional day 3 ET.     

A prospective randomized study comparing the outcome of in-vitro fertilization and embryo transfer following culture of human embryos individually or in groups before embryo transfer on day 2.

A prospective randomized trial of in-vitro fertilization and embryo transfer was undertaken to investigate the reported beneficial effects of culturing preimplantation human embryos in groups, rather than individually. A total of 159 treatment cycles, in which the women were matched for age, basal gonadotrophin concentrations and number of previous attempts, were included in the study. Of these, 78 cycles were randomized to the 'individual culture' group, and 81 cycles were randomized to the 'group culture' group. The groups did not differ in terms of the median number of oocytes or embryos obtained per cycle. There was no statistically significant difference between the two groups in terms of treatment outcome, as assessed by pregnancies or clinical pregnancies.     

Minimizing embryo expulsion after embryo transfer: a randomized controlled study

BACKGROUND: The aim of this work was to modify the embryo transfer technique to prevent expulsion of the embryos by exerting gentle mechanical pressure on the cervix using the vaginal speculum. METHODS: A total of 639 infertile patients undergoing ICSI were prospectively randomized into two groups using sealed dark envelopes. In the study group (n=325) the screw of the vaginal speculum was loosened in order to exert a gentle pressure on the portiovaginalis of the cervix before ejecting the embryos, and was maintained for 7 min afterwards. In the control group (n=314) no pressure was applied on the cervix during embryo transfer and the vaginal speculum was removed after transferring the embryos. RESULTS: The clinical pregnancy rate was significantly higher in the study group than in the control group [207/325 (67%) versus 150/314 (47.8%); odds ratio (OR) 1.39; 95% confidence interval (CI) 1.11-1.74]. The implantation rate was also significantly higher in the study group [304/913 (33.3%) versus 198/920 (21.5%); OR 1.54; 95% CI 1.26-1.89]. CONCLUSIONS: Applying gentle mechanical pressure on the portiovaginalis of the cervix using the vaginal speculum during and after transferring the embryos significantly improved clinical pregnancy and implantation rates.     

Live birth rate is significantly higher after blastocyst transfer than after cleavage-stage embryo transfer when at least four embryos are available on day 3 of embryo culture. A randomized prospective study

INTRODUCTION: In a randomized controlled trial, we assessed whether pregnancy outcome would be improved by extending embryo culture to day 5 and transferring a blastocyst in patients with at least four good-quality embryos on day 3. METHODS: Multifollicular ovarian stimulation was performed with a GnRH agonist in 44% of patients and with a GnRH antagonist in 56%. Overall, 164 patients younger than 37 years fulfilled embryo quality criteria (at least four having at least six cells on the morning of day 3, maximum 20% anucleate fragments) on the third day of culture and were randomized to the day 3 (n = 84) or day 5 (n = 80) groups. Equal numbers of embryos (n = 2) were transferred in each group. RESULTS: Demographics, stimulation parameters and embryological data were comparable in the two groups. Blastocyst-stage transfer resulted in a significantly higher ongoing pregnancy rate [51.3 versus 27.4%; odds ratio (OR) 2.78, 95% confidence interval (CI) 1.45-5.34] and live birth rate (47.5 versus 27.4%; OR 2.40, 95% CI 1.25-4.59) compared with day-3 embryo transfer. A high twin birth rate was observed in both groups (36.8 versus 30.4%; P > 0.05). CONCLUSIONS: A threshold of four good embryos on the third day of embryo culture appears to indicate that the patient will benefit from embryo transfer at the blastocyst stage and have a better chance of achieving a live delivery than with cleavage-stage embryo transfer.     

Effect of using an echogenic catheter for ultrasound-guided embryo transfer in an IVF programme: a prospective, randomized, controlled study

BACKGROUND: Recent evidence showed that ultrasound-guided embryo transfer significantly increases successful implantation compared to the clinical touch method. It has been postulated that new echodense catheters which are more readily detectable by ultrasound may refine transfer techniques even more, thus improving IVF outcome. METHODS: A prospective, randomized, controlled trial comparing IVF outcome for women undergoing embryo transfer under ultrasound guidance by a single healthcare provider with random assignment according to a computer-generated randomization table to either standard soft Wallace catheter (standard catheter group, n=95) or the new echogenic soft Wallace catheter (echogenic catheter group, n=98). RESULTS: The use of the echodense catheter facilitated catheter identification under ultrasound, and thus the duration of the embryo transfer procedure since the loaded catheter was handed to the physician and up to embryo discharge was significantly shorter in the echogenic catheter group as compared with the standard catheter group. There were 39 and 53 clinical pregnancies in the standard catheter (41%) and echogenic catheter (54.1%) groups, respectively. This was not statistically significant (P=0.08) according to the OR (0.6) and CIs (0.33-1.04). However, twin pregnancy rate was significantly increased (P<0.01) with the use of the new catheter which was the underlying source for obtaining significant increase in implantation rate in this group (37.1%) as compared with the standard catheter group (23.2%). CONCLUSION: This pilot study suggests that the use of the echogenic Wallace catheter simplifies ultrasound-guided embryo transfer but not definite benefit in terms of pregnancy rates was obtained. In contrast, the use of the new catheter was associated with a significant increase in the number of twin pregnancies.     

Influence of position and length of uterus on implantation and clinical pregnancy rates in IVF and embryo transfer treatment cycles

In a prospective study of 807 consecutive women shown to have an apparently normal uterus after hysterosalpingography, hysteroscopy or pelvic ultrasonography prior to IVF or intracytoplasmic sperm injection (ICSI) and embryo transfer, the position and length of the uterine cavity was measured routinely at a pre-treatment mock transfer procedure. The apparent length of the uterine cavity was <7 cm in 128 women (group 1), 7-9 cm in 594 women (group 2) and >9 cm in 85 women (group 3). The uterus was noted to be retroverted in 38. 2% (308) women. The embryo transfer catheter was advanced to 5 mm from the uterine fundus based on the previously determined cavity length in all the embryo transfer procedures at 48 h after oocyte collection. Implantation and clinical pregnancy rates were not significantly different with respect to position of the uterus, difficulties encountered in passage of the catheter, mean age of the women, aetiology or duration of infertility or embryology events. An apparently greater cavity length was seen in older and/or parous women, but the difference was not statistically significant. Although the highest implantation and clinical pregnancy rates were seen in women with a cavity length of 7-9 cm (group 2) the differences were not statistically significant: group 1, 18.9 and 36. 7%; group 2, 21.0 and 46.5%; and group 3, 17.3 and 32.9% respectively. The incidence of ectopic pregnancy per reported clinical pregnancy was highest in group 1 women, being 14.9% (7/47) in comparison with group 2 (1.8%, 5/276) and group 3 (0%, 0/27) (P: < 0.0005), suggesting that the size of the uterus is a critical factor in the aetiology of ectopic pregnancy in IVF/ICSI-embryo transfer.     

The usefulness of ultrasound guidance in frozen-thawed embryo transfer: a prospective randomized clinical trial

BACKGROUND: Recent randomized controlled trials have shown that implantation and pregnancy rates were improved with ultrasound-guided embryo transfer compared with clinical touch in fresh IVF cycles associated with supraphysiological ovarian steroid levels. However, the usefulness of ultrasound guidance in frozen-thawed embryo transfer where potential hormonal influences are lacking has not been appropriately investigated. METHODS: A total of 184 consecutive patients undergoing thawed embryo transfer cycles with hormone replacement under pituitary suppression were randomized by computer-generated randomization table to two study groups: 93 had ultrasound-guided (group 1) and 91 had clinical touch (group 2) embryo transfer. RESULTS: There was equal distribution between the two study groups with respect to the main demographic and baseline characteristics of the patients as well as the characteristics of both prior IVF cycles from which embryos were generated and cryopreserved-thawed embryo transfer cycles. However, both pregnancy and implantation rates in group 1 (34.4 and 19.8% respectively) were significantly higher than the corresponding values (19.7 and 11.9%) in group 2. CONCLUSIONS: Ultrasound guidance in frozen-thawed embryo transfer significantly increases pregnancy and implantation rates.     

Modelling the impact of single embryo transfer in a national health service IVF programme

BACKGROUND: Greater use of single embryo transfer (SET) to reduce twin ratesassociated with IVF requires good information on prognosticfactors and appropriate models of treatment outcomes. METHODS: Using data from a cohort of 1198 IVF cycles, we have developeda statistical model of live birth and twin outcomes in termsof routinely measured clinical parameters. From this model,we predict potential outcomes if those who had two embryos transferredhad actually received SET. RESULTS: Embryo quality, age, FSH level, idiopathic diagnosis, spermcount, smoking and alcohol consumption are all significant factorspredicting outcome. Couples with good embryos and good prognosishave a much greater risk of producing twins. In this cohort,to achieve a 10% twin rate would require 55% SET which, withoutselection of appropriate cycles, would lead to a reduction insuccess rate from ca. 21% to 17%. Selecting on the basis oftwin risk can partially mitigate this reduction to give a successrate of 18.5%. CONCLUSIONS: The use of SET to reduce twin rates will lead to a significantreduction in treatment success. Around half this reduction couldbe mitigated with careful selection of patients and cycles,including embryo quality.     

Ultrasound-guided embryo transfer does not offer any benefit in clinical outcome: a randomized controlled trial

BACKGROUND: Ultrasound-guided embryo transfer (ET) is widely suggested as a standard clinical practice that improves overall embryo implantation and pregnancy rates. Various studies of this issue suffer from methodological pitfalls, so that a randomized controlled trial, which overcomes these problems, might be valuable. METHODS: Three hundred women aged <40, who underwent fresh ET, were included in this randomized, double-blind controlled trial. The K-J-SPPE echo tip soft catheter was used for the ultrasound-guided ET and the traditional K-Soft catheter for ETs not using ultrasound. One experienced operator performed all ETs. The primary study outcome was overall pregnancy rate (defined as the number of positive hCG results per transfer). RESULTS: No significant differences between groups were found regarding baseline patient and embryological characteristics, except for male factor and unexplained infertility (higher in the blind and ultrasound-guided ET group, respectively, P < 0.05). Overall pregnancy rates were 53.3 and 51.3% in the ultrasound-guided and blind ET group, respectively. Two ectopic pregnancies were reported in each group. Difficulty in cervical negotiation did not differ between the two groups. CONCLUSIONS: In patients undergoing ET by an experienced operator, ultrasound guidance did not provide any benefit in terms of overall clinical pregnancy and embryo implantation rates.     

A randomized clinical trial comparing recombinant hyaluronan/recombinant albumin versus human tubal fluid for cleavage stage embryo transfer in patients with multiple IVF-embryo transfer failure

BACKGROUND: We aimed to examine the efficacy of using an embryo transfer medium enriched with hyaluronan (HA) to improve implantation in a selected group of patients aged <43 years with repeated (>4) implantation failures after IVF-embryo transfer. METHODS: About 101 patients, meeting our selection criteria, were randomly allocated to undergo embryo transfer either using our routine embryo transfer medium without HA (control group) or a HA enriched commercial embryo transfer medium (study group). The primary outcome was clinical pregnancy rate. RESULTS: After a similar treatment protocol, the ovarian hormonal response, the mean number of ova retrieved and injected per patient, fertilization and cleavage rates and mean embryo quality were comparable between the study and control groups. Although a similar number of embryos was transferred in both groups (3.1 +/- 0.7 versus 2.9 +/- 0.6, mean +/- SD), a significantly higher implantation rate (16.3% versus 4.8%, P = 0.002) and clinical pregnancy rate (35.2% versus 10.0%, P = 0.004) and delivered or ongoing pregnancy rate (31.3% versus 4.0%, P = 0.0005) were observed in the study group. When mean implantation rate per patient was calculated, the difference between the study (0.148 +/- 0.23) and control (0.04 +/- 0.13) group was significant (P = 0.003). CONCLUSIONS: In this selected group of patients after multiple IVF-embryo transfer failures, the use of HA enriched embryo transfer medium is beneficial.     

Day 5 versus day 3 embryo transfer: a controlled randomized trial

Blastocyst transfer has been suggested to improve implantation rate without affecting pregnancy rate. The aim of this study was to compare the pregnancy and implantation rates of day 3 and 5 transfers in a prospective randomized manner. Patients with four or more zygotes were randomly allocated on day 1 to either day 3 or 5 transfers. Fertilization was achieved through regular IVF or intracytoplasmic sperm injection. Zygotes were kept in Medicult IVF medium for day 3 transfers and transferred into G1.2 and G2.2 on day 1 and 3 respectively for day 5 transfers. The morphologically best two or three embryos or blastocysts were chosen for transfer in both groups. Overall pregnancy rates per embryo transfer were the same (39%) in day 3 and 5 transfers. Implantation rates were 21 and 24% for day 3 and 5 transfers respectively. The pregnancy and implantation rates for day 5 transfers were significantly affected by the availability of at least one blastocyst to transfer and the number of zygotes. The number of good quality embryos on day 3 also significantly affected pregnancy and implantation rates on day 5 transfers. Multiple gestation rate, number of abortions and ongoing pregnancies were similar in both groups. In conclusion, day 3 and 5 transfer had similar pregnancy, implantation and twinning rates. Currently, day 5 transfers have no advantages over day 3 transfers.     

Elective single day 3 embryo transfer halves the twinning rate without decrease in the ongoing pregnancy rate of an IVF/ICSI programme

BACKGROUND: Data on the effect of elective single embryo transfer (eSET) on the total and multiple pregnancy rates of an IVF/ICSI programme are reported. METHODS AND RESULTS: A retrospective cohort analysis of eSET was carried out over a 4 year period. A total of 1559 cycles resulted in 1464 transfers; 299 transfers of one top quality embryo (20.4%) and 86 of one non-top quality embryo (5.9%) yielded 149 conceptions (49.8%) with 105 ongoing pregnancies (35.1%) and 26 conceptions (30.2%) with 19 ongoing implantations (22.1%) respectively; 1079 transfers of two (n = 853; 58.3%) or more than two (n = 226; 15.4%) embryos yielded 366 ongoing pregnancies (33.9%). The ongoing pregnancy rates for the years between 1998 and 2001 were 35.9, 27.9, 31.9 and 31.0% per oocyte retrieval and 38.5, 29.4, 34.1 and 33.2% per transfer. There were no differences in pregnancy rates between any of the years. The average ongoing pregnancy rate (>12 weeks) over the 4 years was 31.5% per started cycle and 33.5% per transfer; the average number of embryos transferred decreased from 2.26 (1998) to 1.79 (2001); the multiple pregnancy and twinning rates dropped from 33.6 and 29.5% (1998) to 18.6 and 16.3% (2001) respectively. CONCLUSIONS: Judicious application of eSET can halve the twinning rate while maintaining the overall pregnancy rate.     

Impact of patients' choice for single embryo transfer of a top quality embryo versus double embryo transfer in the first IVF/ICSI cycle

BACKGROUND: The aim of this study was to evaluate the impact of transferring a single top quality embryo in the first IVF/ICSI cycle of patients <38 years old who chose to have one or two embryos transferred. METHODS: A total of 262 patients participated in the study, and 243 transfers were performed: 156 (64%) patients chose the transfer of a single top quality embryo, if available, and two non-top quality embryos if not available; 87 (36%) patients chose to have a double embryo transfer regardless of embryo quality. RESULTS: In the first group an ongoing pregnancy rate of 40% (63/156) with a twin pregnancy rate of 2% (1/63) was achieved. In the second group the ongoing pregnancy rate was 44% (38/87) with 26% (10/38) twin pregnancies. In the patient group with only one embryo transferred, irrespective of the patient's choice, the ongoing pregnancy rate was 43% (54/127) with no twin pregnancies. For the study population as a whole, the ongoing pregnancy rate was 42% (101/243) with 11% (11/101) twins. CONCLUSION: We conclude that the introduction of single embryo transfer in the first IVF/ICSI cycle is highly acceptable in women <38 years old.     

High serum oestradiol concentrations in fresh IVF cycles do not impair implantation and pregnancy rates in subsequent frozen-thawed embryo transfer cycles

High oestradiol concentrations may be detrimental to the success of in-vitro fertilization (IVF) treatment. A total of 1122 women aged <40 years who were undergoing their first IVF cycle were evaluated retrospectively. Serum oestradiol concentrations on the day of human chorionic gonadotrophin (HCG) administration were categorized into three groups: group A <10 000 pmol/l; group B 10 000-20 000 pmol/l and group C >20 000 pmol/l. In fresh cycles, group A had significantly lower pregnancy rates per transfer (16.2 versus 23.7% respectively, P = 0.005, chi(2)) and implantation rates (8.7 versus 11.7% respectively, P = 0.037, chi(2)), when compared with group B. The pregnancy rate per transfer in group C was significantly lower than that in group B (12.1 versus 23.7%, P = 0.049, chi(2)) and group C had the lowest implantation rate (6.4%). In frozen-thawed embryo transfer cycles, implantation rates in groups A, B and C were similar (7.5, 8.1 and 9.6% respectively) and the pregnancy rates were also comparable in all groups. In conclusion, high serum oestradiol concentrations in fresh IVF cycles may adversely affect implantation and pregnancy rates. Embryo quality seemed unaffected as excess embryos from different groups had similar implantation and pregnancy rates in frozen-thawed embryo transfer cycles. The reduced implantation was probably due to an adverse endometrial environment resulting from high serum oestradiol concentrations.     

A health-economic decision-analytic model comparing double with single embryo transfer in IVF/ICSI

BACKGROUND: Single embryo transfer (SET) is the sole strategy with which to reduce the incidence of twins following assisted reproductive technology (ART), but SET may increase the number of ART cycles needed per live-born child. Its cost-effectiveness compared with double embryo transfer (DET) is therefore unknown. METHODS: A decision-analytic model comparing SET with DET was developed. Estimates were obtained from literature, national pregnancy registers and local hospital records. A sensitivity analysis was performed, using pregnancy rates from four published studies. The outcome measure was the cost per child born, calculated from IVF procedure-related, pregnancy-related and neonatal care costs. Neonatal mortality and long-term morbidity costs were not taken into account. RESULTS: Independently of the pregnancy rates used, the SET cost per child born was in all instances the same as with DET, varying from EURO= 9520 (SET) versus EURO= 9511 (DET) to EURO= 12254 (SET) versus EURO= 12934 (DET). CONCLUSIONS: More ART cycles are required to obtain the same numbers of children born following SET compared with DET. Because SET allows the avoidance of twins and thus diminishes pregnancy-related and neonatal care costs, there is no difference in the cost per child born between SET and DET. The real advantage of SET is the avoidance of the very high long-term costs resulting from the increased morbidity of twins after birth.     

The predictive value of using a combined Z-score and day 3 embryo morphology score in the assessment of embryo survival on day 5

BACKGROUND: The purpose of this study was to evaluate the ability of using the Z-score alone, or, in combination with the day 3 embryo morphology score, to predict embryo viability at day 5 from a large cohort of embryos derived from patients undergoing treatment with IVF/ICSI. METHODS AND RESULTS: In this retrospective study, a total of 1894 zygotes from 346 treatment cycles (295 couples) was analysed between January 2001 and May 2002. The Z-scoring system was useful in predicting day 5 embryo survival. The mean +/- SD day 5 embryo survival rates were 78.2 +/- 1.7, 49.0 +/- 2.5, 21.4 +/- 3.2 and 11.8 +/- 5.6% for Z-1, Z-2, Z-3 and Z-4 zygotes groups respectively. Embryos derived from Z-1 scores and grade I day 3 embryo scores showed the best day 5 embryo survival and a very high implantation potential. CONCLUSIONS: These data suggest that a combined evaluation of the Z-score and day 3 embryo morphology is highly predictive of embryo outcome after IVF/ICSI. The Z-score could be of great help in the selection of embryos for cultures extended to later stages. The Z-score alone, or preferably in combination with day 3 embryo morphology, is useful in the determination of the most suitable embryos and the number of embryos for transfer, thus achieving the optimal chance of conception while reducing the risk of high order multiple pregnancy.     

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).     

The impact of the embryo transfer catheter on the pregnancy rate in IVF

BACKGROUND: The aim was to assess whether the type of embryo transfer set used for embryo transfer affects the ongoing pregnancy rate in IVF. METHODS: The TDT set was compared with the K-soft 5000 in a large, prospective, randomized study. Patients were randomized moments before transfer by drawing a consecutively numbered, sealed, opaque envelope indicating the catheter to be used. RESULTS: 2059 embryo transfers in 1296 patients were analysed. The ongoing pregnancy rate was significantly higher in the K-soft group. If the first transfer of a patient (n = 1296) within this study period was analysed, the ongoing pregnancy rates were 27.1 versus 20.5% (P = 0.006). If the analysis is limited to patients that underwent their very first transfer ever (n = 607), the ongoing pregnancy rates were 30.3 versus 20.0% (P = 0.003) in favour of the K-soft. CONCLUSION: We conclude from these data that the type of embryo transfer set used for embryo transfer does affect the ongoing pregnancy rate and that the impact of the variable transfer catheter on the ongoing pregnancy rate increases when the a priori chance of pregnancy increases.