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BACKGROUND: The aim was to analyse multinucleation in relation to its incidence in time and in the population, and its correlation with clinical variables, with other morphological characteristics and with the implantation rate of cleavage stage embryos. METHODS: Retrospective analysis of 10 388 cleaved embryos from 1395 consecutive IVF/ICSI cycles in 700 patients between January 1, 1999 and June 30, 2002. RESULTS: Multinucleation was observed in 3491 (33.6%) embryos in 1107 cycles (79.4%) of 609 (87%) patients, more frequently on day 2 than on day 3: 2848 (27.4%) versus 1567 (15.1%) [relative risk (RR) = 1.82; 95% confidence interval (CI) = 1.72-1.92]. Its incidence increased with fragmentation: 31.0, 34.4 and 36.5% for fragmentation ≤10%, 10-20% or 20-30%. It was increased in stimulation cycles that were shorter (34.9 versus 32.0%, RR = 1.09; 95% CI = 1.03-1.15), required a higher FSH dose (34.6 versus 32.0%, RR = 1.08; 95% CI = 1.02-1.14) and yielded more oocytes (34.5 versus 29.7%, RR = 1.16; 95% CI = 1.08-1.25). Four-cell embryos on day 2 showed minimal multinucleation (16.8%) as well as 8-cell embryos on day 3 (15.5%). Embryos counting both 4 blastomeres on day 2 and 8 on day 3 showed minimal multi nucleation (11.6%). Multinucleated embryos had a decreased implantation rate: 4.3% in single and 5.7% in double embryo transfers. CONCLUSIONS: Multinucleation is a frequently observed phenomenon. It is associated with impaired cleavage and increased fragmentation and is compromising the ongoing implantation rate. Multinucleation should be part of embryo assessment. [ABSTRACT FROM AUTHOR]

Background: The aim was to analyse multinucleation in relation to its incidence in time and in the population, and its correlation with clinical variables, with other morphological characteristics and with the implantation rate of cleavage stage embryos., Methods: Retrospective analysis of 10 388 cleaved embryos from 1395 consecutive IVF/ICSI cycles in 700 patients between January 1, 1999 and June 30, 2002., Results: Multinucleation was observed in 3491 (33.6%) embryos in 1107 cycles (79.4%) of 609 (87%) patients, more frequently on day 2 than on day 3: 2848 (27.4%) versus 1567 (15.1%) [relative risk (RR) = 1.82; 95% confidence interval (CI) = 1.72-1.92]. Its incidence increased with fragmentation: 31.0, 34.4 and 36.5% for fragmentation

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.

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.

For optimal embryo selection in IVF/intracytoplasmic sperm injection (ICSI), knowledge of the implantation potential is essential. This is a retrospective analysis of morphological characteristics and cleavage kinetics of day 3 embryos resulting in an objective assessment of the relative implantation potential of each distinct type of embryo. Therefore transferred embryos were sampled according to their documented implantation behaviour: all embryos without any implantation on the one hand and all those with 100% ongoing implantation on the other. There were 213 such embryos in the latter group of which only seven (3%) had >20% fragmentation and only one embryo (0.5%) showed multinucleation (an embryo containing >20% fragmentation). For this reason, only embryos with < or =20% fragmentation and without multinucleation were analysed. They were split up according to the amount of fragmentation and the number of blastomeres on day 2 and on day 3. For each type, the implanted fraction was calculated, i.e. the number certainly implanted divided by the sum of the number certainly implanted and the number certainly not implanted, thus describing its relative implantation potential. By extrapolation to the entire population it was possible to establish the implantation potential for each type of embryo. Optimal day 3 embryos were calculated to reach a mean of 47% ongoing implantation. By establishing the implantation potential for most embryos, this model also provides useful information about which embryos are worth freezing in a cost-effective cryopreservation policy.

In most in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) programmes approximately one ongoing pregnancy in three is multiple. The need to characterize embryos with optimal implantation potential is obvious. We retrospectively examined all of 23 double transfers resulting in ongoing twins, occurring between January 1, 1996 and May 19, 1997. Characteristics of these top quality embryos were absence of multinucleated blastomeres, four or five blastomeres on day 2, seven or more cells on day 3, and 2 embryos, 11/31 (35%) were multiple. We applied our top quality criteria to the 221 double transfers: 106 transfers with two top embryos resulted in 65 (63%) ongoing pregnancies with 37 (57%) twins, 65 transfers with one top embryo in 38 (58%) ongoing pregnancies with eight (21%) twins. In the group without top embryos, 12/52 (23%) ongoing singletons occurred, with no twins. The corresponding ongoing implantation rates were 49, 35 and 12%. This analysis suggests that single embryo transfer with an acceptable pregnancy rate might be considered if a top quality embryo is available.