Ultrasound-guided embryo transfer: a prospective randomized controlled trial.

BACKGROUND: Recent reports suggested that ultrasound guidance during embryo transfer might improve the pregnancy rate. METHODS: A prospective randomized controlled trial was performed to compare embryo transfer under ultrasound guidance versus the clinical touch method. A total of 800 embryo transfers was studied; 400 were randomized to ultrasound-guided transfers and 400 were randomized to the clinical touch group. Of these, 441 were fresh cycles and 359 were frozen-thawed cycles. RESULTS: The clinical pregnancy rate was 26.0% in the ultrasound-guided group and 22.5% in the clinical touch group; the difference was not statistically significant. The ongoing pregnancy rate was 23.5% in the ultrasound-guided group compared with 19.0% in the clinical touch group and the difference was again not statistically significant. The implantation rate was slightly higher in the ultrasound-guided group (15.3%) than the clinical touch group (12.0%) (P = 0.048). There were no differences in the incidences of ectopic pregnancy, miscarriage and multiple pregnancy between the two groups. CONCLUSIONS: A significant improvement in implantation rate was observed following the use of ultrasound guidance during embryo transfer. The extent of improvement in the pregnancy rate may depend on the specific techniques and methods of embryo transfer used in individual centres.     

Embryo transfer under ultrasound guidance improves pregnancy rates after in-vitro fertilization

Between October 1998 and January 1999, we examined the influence of ultrasound guidance in embryo transfer on pregnancy rate in 362 patients from our in-vitro fertilization (IVF)-embryo transfer programme. These patients were prospectively randomized into two groups: 182 had ultrasound-guided embryo replacement, and 180 had clinical touch embryo transfer. There were no statistically significant differences between the two groups with respect to age, cause of infertility and in the characteristics of the IVF cycle. The pregnancy rate was significantly higher among the ultrasound-guided embryo transfer group (50%) compared with the clinical touch group (33.7%) (P < 0.002). Furthermore, there was also a significant increase in the implantation rate: 25.3% in the ultrasound group compared with 18.1% in the clinical touch group (P < 0.05). In conclusion, ultrasound assistance in embryo transfer significantly improved pregnancy and implantation rates in IVF.     

Transvaginal ultrasound-guided embryo transfer improves pregnancy and implantation rates after IVF.

BACKGROUND: Attempts are constantly being made to improve clinical pregnancy rates after IVF and embryo transfer. Since November 1998, we have gradually been adopting transvaginal ultrasound guidance during embryo transfer. We retrospectively examined the efficacy of this method on pregnancy and implantation rates. METHODS: The results of 846 cycles from our IVF-embryo transfer programme were analysed and comparisons were made between those carried out using ultrasound guidance and those by the clinical touch method. RESULTS: Higher pregnancy and implantation rates (28.9 and 15.2% respectively) were found in the group using the transvaginal ultrasound guidance during embryo transfer compared with those in the group using the clinical touch method (13.1 and 7.0% respectively). The differences were statistically significant (P < 0.01). There was no significant difference in ectopic pregnancy rates between the two groups. CONCLUSION: The use of transvaginal ultrasound-guided embryo transfer significantly improved both pregnancy and implantation rates. Although technically difficult, we suggest its use may maximize the chances of achieving a successful pregnancy outcome.     

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.     

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.     

Ultrasound-guided soft catheter embryo transfers will improve pregnancy rates in in-vitro fertilization

Attempts to improve clinical pregnancy rates after in-vitro fertilization (IVF) and embryo transfer are constantly being made. Two changes in technique of embryo transfer of potential clinical importance were evaluated over two contiguous time periods in order to observe any corresponding change in clinical pregnancy (CP) rate per transfer: (i) embryo transfer catheter; (ii) ultrasound guidance. Catheter choices were hard: Tefcat, Tom Cat, or Norfolk; or soft: Frydman or Wallace. Ultrasound visualization was considered to be excellent/good when the catheter could be followed from the cervix to the fundus by transabdominal ultrasound with retention of the embryo-containing fluid droplet; fair/poor if visualization could not document the sequence of events. Embryo transfers were performed in 518 cycles. CP rates per transfer using soft and hard catheters was 36 and 17% (P < 0.000) respectively. CP rates per transfer for transfers performed with and without ultrasound guidance were 38 and 25% (P < 0.002) respectively. A statistically significant difference was also noted when visualization ranks were compared. CP rates per transfer in all excellent/good ultrasound-guided transfers was 41.5 versus 16.7% for fair/poor transfers (P < 0.038). In conclusion, performance of embryo transfer with a soft catheter under ultrasound guidance with good visualization resulted in a significant increase in clinical pregnancy rates.     

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.     

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.     

Ultrasound measurement of the uterocervical angle before embryo transfer: a prospective controlled study

BACKGROUND: The study aim was to determine whether moulding the embryo transfer catheter according to the uterocervical angle measured by ultrasound could improve pregnancy and implantation rates. METHODS: Patients were alternately allocated to one of two groups. In the ultrasound-guided group (n = 320), the catheter was moulded according to the uterocervical angle measured by abdominal ultrasound. In controls (n = 320), embryo transfer was performed using the "clinical feel" method. RESULTS: Moulding the embryo transfer catheter according to the uterocervical angle significantly increased clinical pregnancy [(OR = 1.57, 95% CI (1.08-2.27)] and implantation rates [(OR = 1.47, 95% CI (1.10-1.96)] compared with the "clinical feel" method. It also significantly reduced difficult transfers [(OR = 0.25, 95% CI (0.16-0.40)] and blood during transfers [OR = 0.71, 95% CI (0.50-0.99)]. Patients with large angles (>60 degrees ) had significantly lower pregnancy rates compared with those with no angle [OR = 0.36, 95% CI (0.16-0.52)]. CONCLUSIONS: Moulding the embryo transfer catheter according to the uterocervical angle measured by ultrasound increases clinical pregnancy and implantation rates and diminishes the incidence of difficult and bloody transfers.     

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.     

Cervical dilatation has a positive impact on the outcome of IVF in randomly assigned cases having two previous difficult embryo transfers

BACKGROUND: The difficulty of embryo transfer has been reported to affect success rates in some centres, but not in others. Cervical dilatation has been proposed as a means to overcome difficult embryo transfer, but consistent criteria for patient selection are lacking. In a prospective randomized study, we examined the influence of cervical dilatation 1-3 months before embryo transfer on the outcome of IVF in cases having difficult embryo transfer in two previously failed IVF cycles. METHODS: Two alternative methods of embryo transfer preparation were evaluated in 283 randomly assigned women having difficult embryo transfers in two previously failed IVF attempts. Randomization was made using a computer-generated random number table. Cervical dilatation before starting any IVF treatment was used in 145 cases, and no dilatation was performed in 138 cases. RESULTS: The cervical dilatation group yielded a significantly higher pregnancy rate than the non-dilated group (40% versus 24%; P < 0.01). Likewise, the implantation rate (24.1% versus 14.9%; P < 0.01) and the live birth rate (34.48% versus 19.56%; P < 0.01) were significantly higher in the dilatation group than in the non-dilated group. CONCLUSIONS: In patients with prior difficult embryo transfer, cervical dilatation 1-3 months before embryo transfer lead to an improved pregnancy rate.     

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.     

Does laparoscopic ovarian diathermy affect the outcome of IVF-embryo transfer in women with polycystic ovarian syndrome? A retrospective comparative study

Controlled ovarian stimulation for IVF and embryo transfer and outcome parameters were compared retrospectively in 31 women with clomiphene-resistant polycystic ovarian syndrome (PCOS). Of these women, 15 had previously undergone laparoscopic ovarian diathermy before IVF (group A, total 22 cycles) and 16 had not had surgical treatment (group B, total 24 cycles). No statistically significant differences were observed in the number of oocytes retrieved, although the number of embryos available for transfer was significantly higher in group B (7.1 +/- 3.8 versus 4.6 +/- 2.7, P < 0.01). The clinical pregnancy rate per embryo transfer appeared to be higher in group B (63.2 versus 41.2%), as did the miscarriage rate (66.7 versus 28.6%), giving an apparent improved ongoing pregnancy rate per embryo transfer in group A (29.4 versus 10.5%), but this was not statistically significantly different. The incidence of severe ovarian hyperstimulation syndrome (OHSS) was apparently higher in group B (4.2 versus 0%), but this difference was not statistically significant. No cases of severe OHSS were seen in group A. Ovarian diathermy does not appear to have a deleterious effect on controlled ovarian stimulation, and the outcome of IVF-embryo transfer may be beneficial in decreasing the risk of severe OHSS and improving the ongoing clinical pregnancy rate.     

Day 3 embryo transfer with combined evaluation at the pronuclear and cleavage stages compares favourably with day 5 blastocyst transfer

BACKGROUND: The respective advantages of day 3 and day 5 embryo transfer are a matter of debate. Previous comparisons did not include pronuclear stage zygote scoring and cumulative success rates (fresh and cryopreserved embryos). METHODS: Patients were randomized prospectively for day 3 or day 5 embryo transfer. Day 3 embryos were selected for transfer and cryopreservation by using combined evaluation at the pronuclear and cleavage stages. RESULTS: There was no difference between day 3 and day 5 fresh embryo transfers as to the rates of pregnancy (58 versus 62%), clinical pregnancy (56 versus 58%), delivery (50 versus 48%), implantation (35 versus 38%) and birth (33 versus 36%) rates. The corresponding values for cryopreserved embryo transfers were also similar. However, day 3 embryo transfer compared favourably with day 5 transfer when the pregnancy (90 versus 66%), clinical pregnancy (85 versus 62%) and delivery (77 versus 52%) rates were calculated per oocyte recovery attempt. CONCLUSIONS: With a selected population of good prognosis patients and our embryo selection criteria, the implantation potential of day 3 and day 5 embryos is equal. Per oocyte recovery attempt, day 3 transfer is more clinically efficient than day 5 transfer, but at least one transfer of cryopreserved embryos is necessary to manifest this superiority.     

Elective single embryo transfer yields good delivery rates in oocyte donation

BACKGROUND: High pregnancy rates have been noted after oocyte donation (OD). Multiple pregnancies should be avoided, because oocyte recipients have an increased risk of obstetric complications. METHODS: We analysed our OD results from 2000-2001 when elective single embryo transfer (eSET) was introduced as a recommended policy for all recipients if at least one good quality embryo was available. The results were compared with those achieved in 1998-1999, when usually two embryos were transferred (double embryo transfer, DET). Between 1998 and 2001, 100 healthy women donated oocytes and 135 fresh embryo transfers were carried out. The mean age of the donors was 31 years and that of the recipient women was 35 years. RESULTS: The proportion of eSET of all OD transfers was 17.1% in 1998-1999 and 61.0% in 2000-2001. There was no statistically significant difference in clinical pregnancy (36.8 versus 45.8%) and delivery rates (31.6 versus 33.9%) per embryo transfer between the two time periods. The proportion of twins declined from 29% (1998-1999) to 10% (2000-2001). The delivery rate was similar after eSET and DET (32.6 versus 32.1% respectively). CONCLUSIONS: By increasing the proportion of eSETs it is possible to reduce the number of twins without affecting delivery rates in oocyte recipients.     

Implantation: Embryo score to predict implantation after in-vitro fertilization: based on 957 single embryo transfers

The purpose of this study was to devise an embryo score to predictthe likelihood of successful implantation after in-vitro fertilization(IVF). Unlike most studies dealing with the influence of embryostage and morphology on pregnancy, our study was based on singlerather than multiple embryo transfers. A total of 957 singleembryo transfers were carried out. No delivery was obtainedafter any of the 99 transfers using 1-cell embryos or embryosobtained after delayed fertilization. In the remaining 858 transfers,the embryos had cleaved. Higher pregnancy rates were obtainedwith embryos displaying no irregular cells (11.7 versus 6.9%;P < 0.01) and embryos displaying no fragmentation (11.5 versus8.1%; P < 0.05). The 4-cell embryos implanted 2-fold moreoften than embryos with more or less cells (15.6 versus 7.4%;P < 0.01). Based on these observations, we devised a 4-pointembryo score in which embryos are assigned 1 point each if they(i) are cleaved, (ii) present no fragmentation, (iii) displayno irregularities, and (iv) have four cells. Both pregnancyrate and take home baby rate were significantly correlated withembryo score. Each point of this score corresponds to a 4% increasein pregnancy rate. Interestingly, pregnancy rate was significantlylower in women aged >38 years (8.2 versus 11.4%; P < 0.05),even though embryo quality was similar regardless of age. Singleembryo transfer allowed us to define a simple and useful embryoscore to choose the best embryo for transfer to optimize IVFand embryo transfer outcome. The use of this embryo score coulddecrease multiple pregnancies after multiple embryo transfers.     

A prospective randomized study to assess the benefit of partial zona pellucida digestion before frozen-thawed embryo transfers

BACKGROUND: Assisted hatching (AH) in fresh embryo transfer (ET) could be associated with increased implantation rates. However, very few prospective randomized studies have specifically addressed the issue of AH during frozen-thawed embryo transfers (FET) cycles, those that have reported controversial results. The aim of this study was to evaluate the benefit of an enzymatic zona pellucida treatment of frozen-thawed embryos before transfer. METHODS: This was a prospective study including 125 non-donor FET cycles from 125 infertile couples. FETs were randomly allocated into AH group (n = 61, embryos pretreated with pronase 5 IU/ml for 1 min at 37 degrees C) or control group (n = 64, untreated embryos). Zona pellucida thickness was measured for each transferred embryo. The main outcome parameters were clinical pregnancy and implantation rates. RESULTS: The two groups were comparable regarding mean women's age, duration and indications of infertility, IVF outcome after fresh ETs, numbers and quality of fresh and frozen embryos, frozen-thawed embryo survival rates and blastomeres survival indexes. Despite a statistically significant decrease of zona pellucida thickness after pronase treatment [(mean +/- SD) 18.5 +/- 2.25 versus 14.5 +/- 2.75 microm; P < 0.0001], implantation (9.6 versus 9.2%) and clinical pregnancy rates (18.0 versus 17.2%) were not statistically different after FETs, with a similar mean number of embryos transferred between AH and control groups, respectively. CONCLUSION: Within the constraints of our protocol, partial enzymatic digestion of zona pellucida by pronase was not related with any benefit of the FET outcome especially concerning the implantation ability of frozen-thawed embryos.     

Training of providers in embryo transfer: what is the minimum number of transfers required for proficiency?

BACKGROUND: Embryo transfer represents one of the most critical procedures in the practice of assisted reproduction. The objective of this study was to identify retrospectively the minimum number of embryo transfers required to train providers properly in this skill. METHODS AND RESULTS: The study group consisted of 204 patients who received embryo transfers between January 1996 and March 2000 in a university-based programme of assisted reproduction. The main outcome measure was clinical pregnancies per embryo transfer. Five Fellow trainees performed a total of 204 embryo transfers for an overall pregnancy rate of 45.5% per embryo transfer (93/204). In comparison, the programme pregnancy rate per transfer for experienced providers was 47.3% (560/1179). A chronological graph of each individual trainee's experience for the first 50 embryo transfers performed suggested a lower initial pregnancy rate for three of the five trainees. To determine whether a learning curve might exist, results of the first 25 transfers were compared as a subgroup with the second 25 transfers. Pregnancy rates were lower for the 1-25 transfer subgroup than in the 26-50 subgroup for three of the five Fellow trainees, although the difference was not statistically significant. CONCLUSION: Clinical pregnancy rates of Fellows-in-training were indistinguishable statistically from those of experienced staff by 50 transfers.     

Turner's syndrome and pregnancies after oocyte donation

A total of 20 clinical pregnancies was achieved among 18 women with Turner's syndrome who were treated in an oocyte donation programme. The oocytes were donated by voluntary unpaid donors. A mean of 1.8 embryos per transfer was given to each recipient by way of 28 fresh and 25 frozen embryo transfers. With fresh and frozen embryos, 13 and seven pregnancies respectively were achieved. The clinical pregnancy rate per fresh embryo transfer was 46%, and the implantation rate 30%, being similar to the corresponding rates among our oocyte recipients with primary ovarian failure in general. The corresponding rates with frozen embryos were 28 and 19%. Of these pregnancies, 40% ended in miscarriage. This high rate may be explained by uterine factors. Six women were hypertensive during pregnancy, a rate comparable with that in other oocyte donation pregnancies. All these women delivered by Caesarean section. Pregnancy and implantation rates after oocyte donation were high in women with Turner's syndrome, but the risk of cardiovascular and other complications is high. Careful assessment before and during follow-up of pregnancy are important. Transfer of only one embryo at a time to avoid the additional complications caused by twin pregnancy is recommended.     

Oocyte and embryo donation: evaluation of 412 consecutive trials.

A total of 199 patients (412 consecutive cycles) were treated by oocyte-embryo donation in 336 replacement cycles. Of these, 296 involved intra-uterine embryo transfers, 38 zygote intra-Fallopian transfers (ZIFT) and two gamete intra-Fallopian transfers (GIFT). Of the 336 replacements, 244 (73%) constituted transfers of fresh concepti and 92 (27%) of frozen-thawed ones. A total of 85 pregnancies were achieved of which 16 ended in preclinical abortions, giving a clinical pregnancy rate of 34.7% per patient, 20.5% per transfer and a take-home baby rate of 29.1% per patient. The pregnancy rate was significantly higher (P less than 0.05) following fresh gamete or embryo replacement (23%; 56/244) than following that of frozen-thawed embryos (14.1%; 13/92). No significant difference was observed when intra-Fallopian replacement was applied (27.5%; 11/40) as opposed to intra-uterine (19.6%; 58/296). Ovarian function was not found to be of significant importance to the achievement of pregnancies after oocyte donation since comparable pregnancy rates per replacement and per started cycle were obtained in patients with ovarian failure and in those with functional ovaries (19% and 15.4%; 24.2% and 20.2% respectively). Comparison of the implantation and abortion rates between these two groups did not reveal any significant difference (11.1% and 11.1% versus 14.8% and 16.6%). The highest pregnancy rate among patients with ovarian failure was observed in those with primary ovarian failure (26.4%; 14/53), while the lowest was among women who had received chemotherapy and/or radiotherapy (9%; 1/11).(ABSTRACT TRUNCATED AT 250 WORDS)