Single embryo transfer is an option in frozen embryo transfer

BACKGROUND: A good strategy to decrease multiple pregnancy rate in assisted reproduction technology (ART) is the use of single embryo transfer (SET). METHODS: This retrospective study analysed 1647 frozen embryo transfers carried out during 1998-2003 in Helsinki University Central Hospital; of these, 872 were double embryo transfers (DETs) and 775 SETs. The SET group included 140 (18.1%) elective SETs (eSETs). RESULTS: The yearly rate of SETs in frozen cycles increased from 28 to 66%. Overall, the clinical pregnancy rate per frozen embryo transfer was 30.7% and the delivery rate 22.6%. The delivery rate was significantly higher in DET cryocycles than in SET cryocycles (25.7 versus 19.2%, respectively; P < 0.01). In DET cryocycles, the multiple delivery rate was 21.9%, 10 times higher than that observed in cryocycles with SET (2.0%) (P < 0.0001). When eSET was applied, no difference in delivery rate was observed when compared with cryocycles with DET (28.6 and 25.7%, respectively). CONCLUSIONS: SET can be used in frozen cycles to reduce multiple delivery rates.     

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.     

1169例冻融胚胎移植周期的临床妊娠结局分析

目的探讨影响冻融胚胎移植(FET)妊娠结局的相关因素。方法回顾分析2017年1月至2019年12月在深圳市妇幼保健院行FET的1169对夫妇的临床数据,采用单因素分析和Logistic多因素回归分析探讨FET妊娠结局的相关因素。结果1169个FET周期的临床妊娠率为50.13%;单因素分析表明,年龄>35岁、不孕年限>6年显著降低胚胎种植率和临床妊娠率(P<0.01),但囊胚或多个优胚数目移植可提高胚胎种植率和临床妊娠率(P<0.01);移植多个胚胎提高胚胎种植率(P<0.05),但子宫内膜厚度>12 mm提高临床妊娠率(P<0.05)。多因素Logistic回归分析显示年龄增加和优胚移植数目减少是临床妊娠率的危险因素(P<0.01)。结论患者年龄和移植优胚数目是影响FET的主要因素;年龄增加是临床妊娠结局的危险因素。     

Frozen embryo transfers: implications of clinical and embryological factors on the pregnancy outcome

BACKGROUND: Frozen embryo transfers are characterized by impaired pregnancy outcome and increased incidence of pregnancy loss as compared with fresh IVF/ICSI embryo transfers. In this study, we performed a retrospective analysis of clinical and embryological factors that potentially influence the outcome of frozen embryo transfer. METHODS: We reviewed the outcome of 1242 frozen embryo transfers with respect to the age of the woman, the method of fertilization, embryo quality before and after freezing and the number of embryos transferred. RESULTS AND CONCLUSIONS: The pregnancy (positive hCG) and clinical pregnancy rates were 25.8 and 21.1%, respectively. A total of 107 (33.3%) of the 321 pregnancies identified by a positive hCG test miscarried either before (18.4%) or after (15%) the clinical recognition of gestational sac(s). The delivery rate for the frozen embryo transfers analysed was 17.2%. Our data revealed that the delivery rate after frozen embryo transfer was dependent on both the woman's age and the quality of embryos transferred, at the same time being unaffected by IVF/ICSI treatment. In addition, the increased woman's age at IVF/ICSI treatment was identified as the only parameter elevating the biochemical pregnancy rate, whereas the clinical abortion rate was found to be unrelated to the clinical or embryological parameters studied.     

A randomized double-blind controlled study of the efficacy of laser-assisted hatching on implantation and pregnancy rates of frozen-thawed embryo transfer at the cleavage stage

BACKGROUND: Assisted hatching (AH) in fresh embryo transfer (ET) cycles increases the implantation and pregnancy rates, especially in women with a poor prognosis, repeated implantation failures and in older women. Little information exists in the literature regarding the role of AH in frozen-thawed embryo transfer (FET) cycles. METHODS: Embryos were cryopreserved at the cleavage stage. On the day of FET, 160 patients were randomized according to a computer-generated randomization list in sealed envelopes into the AH group and the control group. The patients and the clinicians were blinded to the group assigned. In the AH group, the outer half of the zona pellucida over a quarter of the diameter of zona was removed using a 1480 nm non-contact laser. RESULTS: The two groups were comparable in terms of demographic characteristics, ovarian response of the stimulated cycle and quality of fresh and frozen-thawed embryos. No differences in implantation, pregnancy and multiple pregnancy rates were found between the two groups. There was a non-significant trend of a higher implantation rate in the AH group when the zona thickness was > or = 16 mm. CONCLUSION: Laser AH did not improve the implantation rate of FET cycles and should not be performed routinely in all frozen-thawed embryos at the cleavage stage.     

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.     

Elective single embryo transfer in women aged 36-39 years

BACKGROUND: The elective single embryo transfer policy is the only effective strategy known to minimize the risk of multiple pregnancy. However, little is known about its applicability to women older than 35 years. METHODS: Analysis was carried out on 1224 fresh IVF/ICSI cycles with embryo transfer and 828 frozen embryo transfer (FET) cycles of women aged 36-39 years. In the fresh cycles, 335 elective single top quality embryo (eSET), 110 elective single non top quality embryo (nt-eSET), 194 compulsory single embryo (cSET) and 585 double embryo transfers (DET) were carried out. RESULTS: Pregnancy rate/embryo transfer (33.1 versus 29.9%) and live birth rate (26.0 versus 21.9%) in fresh cycles did not differ significantly between the eSET and the DET groups. However, women in the eSET group had a higher cumulative pregnancy rate (54.0% versus 35.0%) and a higher cumulative live birth rate (41.8% versus 26.7%, P < 0.0001) compared with those in the DET group. The cumulative multiple birth rate in the eSET group was 1.7%, whereas in the DET group it was 16.6% (P < 0.0001). CONCLUSIONS: The eSET policy can be applied also to patients aged 36-39 years, reducing the risk of multiple birth and increasing the safety of assisted reproduction technique (ART) in this age group.     

Uterine position at real embryo transfer compared with mock embryo transfer

BACKGROUND: The purpose of this study was to determine the consistency in the uterine position between mock and real embryo transfer. METHODS: We reviewed 996 consecutive embryo transfer cycles (585 patients); 74% of patients had an anteverted (AV) uterus and 26% had a retroverted (RV) uterus at mock embryo transfer. All mock and real embryo transfers were performed under abdominal ultrasound guidance. RESULTS: Of 623 fresh embryo transfers in patients with an AV uterus at mock embryo transfer, only 2% became RV, while 55% of 213 embryo transfers in patients with an RV uterus on mock embryo transfer converted to AV at real embryo transfer (P < 0.0001). For frozen-thawed embryo transfer, 12% of AV uteri at mock embryo transfer became RV, while 33% of RV uteri became AV (P = 0.01). CONCLUSIONS: Our data suggest that an RV uterus at mock embryo transfer will often change position at real embryo transfer. Misdirecting the embryo transfer catheter can be avoided by accurate knowledge of the uterine position at the time of embryo transfer, which can be more accurately assessed by routine ultrasound guidance. Additionally, patients with an RV uterus at mock embryo transfer should still present with a full bladder for embryo transfer, since a significant number will convert to an AV position.     

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.     

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.     

The presence of blood in the transfer catheter negatively influences outcome at embryo transfer

BACKGROUND: Embryo transfer (ET) influences pregnancy rates in patients undergoing assisted reproduction. Data are conflicting as to which variables affect ET success. This study examines variables that may affect outcome after ET in assisted reproductive technology patients who had high-quality embryos transferred. METHODS: Over a 23 month period, 669 consecutive cycles were examined. Only patients having grade I and grade II embryos, or blastocyst transfers, were included in this retrospective analysis. A total of 584 consecutive cycles met study criteria. At the time of ET, the following variables were recorded: aborted first attempt at ET; presence of blood and/or mucus in or on the transfer catheter after ET; ease of ET as judged by provider; need for mock embryo transfer immediately before the actual transfer and retention of embryos in the transfer catheter. These variables were retrospectively analysed for their impact on implantation rate (IR) and clinical pregnancy rate (CPR). RESULTS: There were 290 gestations (49.7% CPR). Multiple attempts at ET, subjective difficulty of ET, performance of a sham pass immediately prior to embryo transfer, and presence of mucus on or in the catheter did not affect the CPR or IR. No difference was noted in the mean age of patients having or lacking any of these factors. There was a significant association between the presence of blood on or in the catheter and decreased IR (P = 0.015) and CPR (P = 0.004). Retained embryos also decreased IR (P = 0.03). Multivariable analysis confirmed that the presence of blood on the transfer catheter was the most important of these transfer characteristics in predicting IR (P = 0.042) and CPR (P = 0.018). CONCLUSIONS: These results suggest that when only high-grade embryos or blastocysts are transferred, the presence of blood on the catheter is associated with decreased IR and CPR in assisted reproduction.     

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.     

Ultrasound-guided embryo transfer and the accuracy of trial embryo transfer

BACKGROUND: Studies have suggested that ultrasound-guided embryo transfer (UG-ET) may improve the outcome in IVF; however, several factors may account for the improvement in pregnancy rate. This study examines the use of ultrasound to determine the accuracy of trial transfer (TT) in preparation for ET. METHODS: Sixty-seven consecutive patients prospectively underwent UG-ET over a 2 month period. Total cavity length by US was compared with the length noted by TT. A difference of > or = 1 cm was considered significant. All embryos were placed within 1-2 cm of the fundus by US. RESULTS: Twenty patients (29.9%) had a difference of > or = 1 cm and 13 patients (19.4%) had a difference of < or = 1.5 cm. Patients with a difference of > or = 1 or > or = 1.5 cm had a significantly greater depth at transfer (P < 0.001) and uterine cavity length (P < 0.001) when compared with patients without a difference. Clinical pregnancy, implantation, delivery and overall miscarriage rates did not differ between patients with a difference of > or = 1 or > or = 1.5 cm versus no difference. There were no ectopic pregnancies. CONCLUSIONS: Nineteen percent of patients had a discrepancy of > or = 1.5 cm and approximately 30% had a difference of > or = 1 cm from TT at UG-ET, suggesting a benefit to UG-ET. A large prospective randomized trial comparing UG-ET with blind transfer is required to assess further if UG-ET should be used in all cases of ET.     

Obstetric and neonatal outcome after single embryo transfer

BACKGROUND: Single embryo transfer (SET) pregnancies practically lack vanishing twins and may be associated with improved neonatal outcome. Our objective was to compare the obstetric and neonatal outcome of SET singletons with the outcome of singletons following double embryo transfer (DET) and spontaneous conception. METHODS: A 7-year (1997-2003) cohort of fresh SET (n = 269) and DET (n = 230, including 25 vanishing twins) cycles resulting in singleton birth at Helsinki University Central Hospital, Finland, was linked to the Finnish Medical Birth Register and the obstetric and neonatal outcome data compared with that from 15 037 spontaneously conceived singleton pregnancies. RESULTS: The obstetric and neonatal outcome of the SET group was comparable to that in the DET group. Compared with the comparison cohort, gestational hypertension (P = 0.005), placenta praevia (P < 0.001), preterm contractions (P = 0.01) and maternal hospitalization (P < 0.001) was more typical of women in the SET group. After adjusting for age, parity and socio-economic status the SET pregnancies showed increased risks of Caesarean section [odds ratio (OR) 1.54 with 95% confidence interval (CI) 1.18-2.00], preterm birth (OR 2.85; 95% CI 1.96-4.16) and low birthweight (OR 2.01; 95% CI 1.19-3.99) compared with the comparison cohort. CONCLUSIONS: Our results indicate that subject- and infertility-related mechanisms other than the number of transferred embryos influence the neonatal outcome of singleton IVF pregnancies.     

Three blastocyst stage embryo transfer resulting in a quintuplet pregnancy

High-order pregnancies are associated with high morbidity and mortality and the incidence is increased as a drastic complication of assisted reproductive technology. This case presents a high-order pregnancy achieved by transfer of three blastocyst stage embryos resulting in a quintuplet pregnancy including a monochorionic triplet. Following the selective termination of the monochorionic triplet, two healthy children were born. The mechanism of monochorionic development and its association with assisted reproductive technology are discussed.     

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.     

Successful fertilization and pregnancy outcome in in-vitro fertilization using cryopreserved/thawed spermatozoa from patients with malignant diseases.

Cryopreservation of spermatozoa before treatment is the only proven effective method available to circumvent the sterilizing effect of therapy in some patients with malignant diseases. Because of impaired sperm quality after freezing and thawing in-vitro fertilization/embryo transfer (IVF/ET) was indicated in 10 patients (12 cycles) during 1986-1990. The patient's mean age was 33.4 +/- 1.6 years. The following diagnoses were made: seminoma (1), testicular carcinoma (3), leiomyosarcoma of the prostate (1), Wegener's granulomatosis (1), non-Hodgkin's (1) and Hodgkin's lymphoma (3). When motile spermatozoa could be recovered after thawing, the total fraction of motile spermatozoa after swim-up separation ranged from 0.2 to 4.2 x 10(6) spermatozoa/ml (eight patients, nine cycles). In all these cases, insemination was performed with multiple oocytes per dish. Fertilization was achieved when swim-up recovered a mean of 1.8 +/- 0.5 x 10(6) spermatozoa/ml and when insemination was performed with at least a calculated concentration of motile spermatozoa of 1 x 10(5) spermatozoa/oocyte. The fertilization rate of preovulatory oocytes was 60%. Four patients achieved a pregnancy: two of them delivered a single healthy baby, one delivered triplet healthy babies and one had a preclinical abortion. In two patients (three cycles), no motile spermatozoa were recovered after thawing, and micromanipulation of oocytes for assisted fertilization was performed. Although fertilized oocytes were transferred, those couples did not achieve a pregnancy. Patients with lymphopathies had the best results, whilst those with testicular neoplasms had the poorest outcome, thus suggesting a poor gametogenic function in the non-affected testis. These results give hope to some patients with malignant diseases to maintain their reproductive capacity through sperm banking and IVF/ET.     

Comparative analysis of pregnancy rates after the transfer of early dividing embryos versus slower dividing embryos

BACKGROUND: We compared retrospectively the pregnancy outcome in two subgroups of ICSI patients, using early division (26 h post injection) to the 2-cell stage as a criterion for embryo quality and viability (ability to produce a pregnancy). METHODS AND RESULTS: In the early dividing embryo (EDE) group, at least one of the transferred embryos was early dividing. In the late dividing embryo (LDE) group, no early dividing embryo was transferred. Additionally, tubal and uterine transfer in the two groups was also evaluated. Clinical pregnancy rates in the EDE group were significantly increased when compared with that in the LDE group (41.3 versus 20.0%). This was also true for ongoing pregnancy rates (33.3 versus 16.3%). The tubal transfer route showed increased (but not significant) ongoing pregnancy rates when compared with uterine transfer in both EDE (38.5 versus 25.0%) and LDE (22.7 versus 8.3%) groups respectively. In uterine transfer cycles, however, clinical pregnancy rates for EDE were significantly increased compared to LDE (37.5 and 11.1% respectively). The baby rate (number of live babies/embryos transferred) was also significantly increased in the EDE group and the tubal transfer group. Statistical analysis of pregnancy outcome, adjusted for the total number of embryos transferred (expressed as percentage risk difference - %RD), resulted significantly in favour of EDE compared to LDE (RD = 18%, P = 0.02). When adjusted for the combined factors: total number of embryos transferred, EDE and LDE, the pregnancy outcome result was significantly in favour of tubal transfer compared to uterine transfer (RD = 15%, P = 0.05). Pregnancy results of the LDE group only were significantly better in the tube compared to the uterus (RD = 19%, P = 0.04) but not significantly so for the EDE group (RD = 10%, P = 0.4). CONCLUSION: Early division is associated with embryo quality and a very easy and successful embryo transfer selection method. Our results also suggest that when EDE are available, both tubal and uterine embryo transfer can be considered. When only LDE are available, however, tubal transfer should be the preferred transfer route.     

Ultrasound-guided embryo transfer improves pregnancy rates and increases the frequency of easy transfers

BACKGROUND: Recent reports have suggested that ultrasound (US) guidance during embryo transfer might improve pregnancy rates. METHODS: A prospective randomized (computer-generated random table) trial was performed to compare embryo transfer under abdominal US guidance (n = 255 women) with clinical touch embryo transfer (n = 260). RESULTS: The clinical pregnancy rate was 26.3% (67/255) in the US-guided transfer group compared with 18.1% (47/260) in the clinical touch transfer group (P < 0.05). The implantation rate was 11.1% (100/903) in the US group compared with 7.5% (66/884) in the clinical touch group (P < 0.05). US-guided transfer was associated with a decrease in the difficulty of the transfers: 97% of transfers were easy in the US-guided group compared with 81% in the clinical touch group (P < 0.05). CONCLUSIONS: US-guided embryo transfer increased pregnancy and implantation rates in IVF cycles, as well as the frequency of easy transfers. It is suggested that the decrease in cervical and uterine trauma can play a role in the increase in pregnancy rates associated with US-guided transfer. It is recommended that embryo transfer should be performed under US guidance.     

The relative myth of elective single embryo transfer

The option of single embryo transfer (SET) has recently dominated the pages of this and other medical journals. Opinions, in regards to the utility of such an approach, appear to differ between Europe and the US. While US guidelines promote a more individualized approach, European opinions, at times, even advocate mandated practice patterns. The European approach, however, fails to recognize the rather significant differences in supportive arguments between the historical switch from multiple embryo transfers to 2-embryo transfers and the current discussion, favouring a switch from 2-embryo transfer to elective (e)-SET. In the former, a significant risk of (at times, high-order) multiple pregnancies was reduced without loss of pregnancy potential. In the latter, a comparably relatively low twinning risk is reduced at the expense of declining pregnancy rates, a need for more treatment cycles, a potential delay in treatment success and, potentially, higher treatment costs. These consequences of e-SET, together with the preference of some infertility patients to actually conceive twins, raise serious questions about the wide utilization of e-SET, as has been propagated by many authorities. According to US guidelines, e-SET, therefore, appears to represent an appropriate transfer option for only a small minority of IVF patients. Argument in favour of indiscriminate SET appears unrealistic and should be reconsidered.