Human Reproduction, Vol. 14, No. 9, 2392-2395,
September 1999
© 1999 European Society of Human Reproduction and Embryology
Elective transfer of one embryo results in an acceptable pregnancy rate and eliminates the risk of multiple birth
1 Infertility Clinic, The Family Federation of Finland, PO Box 849, FIN-00101, Helsinki, 2 Department of Obstetrics and Gynaecology, Helsinki University Central Hospital, PO Box 140, FIN-00029 HUCH, Finland and 3 Department of Obstetrics and Gynaecology, Karolinska Institute, Huddinge Hospital, S-14186, Sweden
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Abstract |
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To avoid multiple pregnancies without compromising pregnancy rates (PR) is a challenge in assisted reproduction. We have compared pregnancy results among 74 elective one-embryo transfers (group 2) and 94 transfers where only one embryo was available (group 1). All the fresh embryo cycles during 1997 in two clinics in Helsinki were analysed, and cumulative PR among these couples after frozen–thawed embryo transfers up to June 1998 were counted. In group 2, where at least two embryos were available for transfer, and only one was transferred on day 2 or 3, the PR per embryo transfer was 29.7%. In group 1, the PR per embryo transfer was 20.2%. In group 2, the cumulative PR after frozen–thawed embryo transfers was 47.3% per oocyte retrieval. Over the same time, 742 two-embryo transfers were carried out. The PR per embryo transfer was 29.4% in these subjects, but 23.9% of these pregnancies were twins. The implantation rates, as well as the PR, were highest when the embryos were at the four- to five-cell stage on day 2 (35.8 versus 9.7% compared with the two- to three-cell stage, P < 0.001) or at the six- to eight-cell stage on day 3 (45.5%). The PR per embryo transfer was higher when a grade 1 or 2 embryo was transferred compared with a grade three embryo (34.0 and 26.7% versus 8.8% respectively, P < 0.05). In women 35 years or younger, the PR per elective one-embryo transfer was 32.8%. The corresponding figure in women older than 35 years was 18.8%. On the basis of these results, elective one-embryo transfer can be highly recommended, at least in subjects who are younger than 35 years of age, and who have grade one or grade two embryos available for transfer.
Key words: embryo transfer/implantation rate/pregnancy rate/single embryo
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Introduction |
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The main factor increasing obstetric risk and adverse perinatal outcome in assisted reproductive techniques is the high rate of multiple pregnancy in most in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) programmes (Addor et al., 1998
). In a large survey, increasing the number of transferred embryos to more than two results in a higher rate of multiple birth, without necessarily improving the overall success rate (Templeton and Morris, 1998). Probabilities have been calculated for singleton and multiple pregnancies as a function of the number of embryos transferred and the implantation rate (Martin and Welch, 1998). To avoid triplet pregnancies, many European IVF centres have accepted the policy of transferring only two embryos (Staessen et al., 1993; Coetsier and Dhont, 1998). However, the number of twin pregnancies after two-embryo transfer is still high, increasing the health care costs for one IVF newborn 5.4-fold compared with other newborns (Gissler et al., 1995).
Many investigators have presented low pregnancy rates (PR) after transfer of one single embryo (Elsner et al., 1997). These results, however, originate from transfers with only one embryo available. In a prospective setting, when the best embryo can be selected for transfer, implantation rates associated with elective single embryo transfer are likely to be higher. The following factors are known to be associated with favourable prognosis: age <36 years, first, second, or third treatment cycle and more than three embryos available for transfer (Coetsier and Dhont, 1998).
One of the main challenges in the field of assisted reproductive technology is to avoid multiple pregnancy without significantly lowering the overall PR. The obstetric and perinatal risks as well as the impact of a multiple pregnancy on the family should be considered individually. Because we want to give objective information to the couples involved, we studied the PR during 1 year in our infertility clinics, in cases where only one embryo was transferred, and compared cycles with only one embryo available, and elective transfer of one embryo.
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Materials and methods |
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During 1997, all subjects with transfer of a single embryo in the Infertility Clinics of the Family Federation of Finland and Helsinki University Central Hospital were studied. The ovarian stimulation regimen, oocyte collection, IVF and ICSI procedures and the embryo transfer method were similar in both clinics, and have been reported elsewhere (Hovatta et al., 1995
; Tiitinen et al., 1995; Simberg et al., 1998). Briefly, long luteal phase down-regulation with nafarelin (Synarela, Syntex Nordica AB, Södertälje, Finland) or buserelin (Suprecur, Hoechst AG, Frankfurt, Germany) was used and, after 2 weeks, suppression was confirmed by transvaginal sonography (TVS). Ovulation induction was commenced with highly purified human follicle-stimulating hormone (FSH; Fertinorm-HP, Laboratories Serono S.A., Aubonne, Switzerland) or recombinant FSH (recFSH; Gonal-F, Laboratories Serono, or Puregon, Organon, Oss, The Netherlands). Human chorionic gonadotrophin (HCG; Pregnyl, Organon, or Profasi, Laboratories Serono) was given 36–38 h before oocyte retrieval. Embryo transfer was performed 2 days, or occasionally 3 days, after oocyte retrieval. Micronized vaginal progesterone (Lugesteron, Leiras, Tampere, Finland) was used for luteal support. Clinical pregnancy was confirmed by TVS at the sixth or seventh week of pregnancy.
The embryos were cultured in standard media (IVF-500, Scandinavian IVF Science, Gothenburg, Sweden or IVF medium, MediCult, Copenhagen, Denmark). The cleavage rates and embryo grading were assessed 48–52 h after oocyte retrieval. The embryos were graded according to the number of blastomeres and the amount of fragmentation. The following grades were used: grade 1: no fragments, grade 2: <20% fragmentation, grade 3: 20–50% fragmentation and grade 4: fragmentation >50%. Cryopreservation and thawing were carried out using standard protocols with either 1,2-propanediol (PROH) (Lassalle et al., 1985) or dimethylsulphoxide (DMSO) (Van Steirteghem et al., 1987). The frozen–thawed embryos were transferred as described previously (Tiitinen et al., 1995; Simberg et al., 1998), during either a natural cycle after a luteinizing hormone (LH) surge measured by a home test kit (Clearplan, Unipath, Bedford, UK), or a hormone replacement cycle.
During 1997, a total of 910 embryo transfers was carried out. In 742 cases two embryos were transferred and in 168 cases a single embryo was transferred. Only one embryo was available and transferred in 94 cycles (group 1). In 74 cycles, elective one-embryo transfer was carried out (group 2), and additional embryos were cryopreserved. The three main indications for elective one-embryo transfer were: subject's wish, risk of ovarian hyperstimulation syndrome (OHSS) and various medical reasons. These included diabetes mellitus, uterine malformation, history of cervical incompetence or hysterotomy, and indication for prenatal diagnosis. The mean age of the women was 35 years (range 24–42 years) in the one-embryo group and 34 years (range 23–42 years) in the two-embryo transfer group.
The implantation rate and clinical PR per embryo transfer were calculated. Correlation between clinical implantation rate and embryo quality as revealed by cleavage and fragmentation status was analysed. The cumulative PR per subject after transfer of both fresh and frozen–thawed embryos before 1st July 1998, as well as the outcome of pregnancies were analysed. Statistical analysis was performed using the 
2 test.
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Results |
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The clinical PR per transfer was 29.4% when two embryos were transferred. Of these pregnancies, 23.9% were multiple. In the one-embryo transfer groups the clinical PR were 20.2% in group 1 and 29.7% in group 2 (Table I
). There were no differences in the results between IVF and ICSI embryos (data not shown). Forty-eight (51%) embryo transfers in group 1 and 48 (65%) of those in group 2 were first attempts at IVF. The clinical PR and pregnancy outcome according to different indications when one embryo was transferred, are presented in Table II. In the elective transfer of one embryo (group 2), the PR was 32.8% in subjects <35 years of age and 18.8% in those >35. When only one embryo was available, the PR did not relate to the age of the women, being 20.4 and 20.0% respectively.
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The highest implantation rates were obtained when four- to five-cell stage embryos were transferred on day 2 after oocyte retrieval (35.8%) or when six- to eight-cell stage embryos were transferred on day 3 (45.5%). Implantation rates according to cleavage stage and grade of the embryo are presented in Table III
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The outcomes of pregnancies in the one-embryo transfer groups are presented in Table II
. Altogether, 19.6% have had a live birth. Of the 74 subjects in group 2, 47 had had at least one frozen–thawed embryo transfer by the end of June 1998 (Table IV). By that time, the cumulative PR was 47.3% per oocyte retrieval in subjects from whom more than one embryo was obtained, and 15 of the 39 non-pregnant subjects still have frozen embryos in storage.
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Discussion |
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The objective of all infertility treatments should be the birth of a healthy child. In the World Collaborative Report on In Vitro Fertilization (1997), figures for 1995 show that 24.7% of the pregnancies are twin, 4.1% are triplet and 0.2% are quadruplet. No decrease in the rate of multiple pregnancy is seen in the preliminary data for 1996. According to a recent report covering all the IVF pregnancies in Sweden in 1982–1996 (Socialstyrelsen, 1998
), the pregnancy and neonatal complications observed in assisted reproductive technology pregnancies were almost entirely due to multiple pregnancies, the majority of which were twin pregnancies. The rate of prematurity (<37 weeks) among twin pregnancies was 47.3%, but only 11.2% among singletons. The policy of transferring only one embryo is therefore extremely important. In our retrospective analysis, the PR after elective one-embryo transfer was 29.7% per cycle, which we consider to be very acceptable. The cumulative PR in these subjects, 47.9% per oocyte retrieval, at a time point when some subjects still have frozen embryos in storage, is even more encouraging. Among two-embryo transfers carried out over the same time period, the PR of 29.4% was not higher than in the elective one-embryo transfer group, but 23.9% of the pregnancies were multiple.
In many countries, more than three embryos are still transferred. This has led to the practice of embryo reduction in pregnancies with three or more fetuses. Embryo reductions, when carried out by experienced clinicians, still carry a 10% risk of miscarriage (Evans et al., 1998). These procedures are not without risks for the newborn (Geva et al., 1998). They are mentally extremely stressful for the couples and many regard them as ethically problematic. Embryo reductions can be completely avoided by transferring only one embryo at a time.
When aiming for individualized transfer policy, we have to consider the probability of the embryo implanting and the subject conceiving. The quality of the embryo is probably the most important factor which predicts the outcome of transfer. One-embryo transfers offered us a unique possibility to relate embryo quality to the implantation rate. In agreement with earlier reports (Staessen et al., 1992; Giorgetti et al., 1995; Roseboom et al., 1995; Tasdemir et al., 1995), embryo quality correlated with the PR. After transfer of grade 1 embryos and grade 3 embryos, the PR were 34.0 and 8.8% per embryo transfer respectively. No pregnancies followed the six grade 4 embryo transfers. Transfer of these poor quality embryos was carried out in cases where there was only one embryo available. If only grade 3 embryos are available, it would be justified to transfer two embryos at a time, and grade 4–5 embryos should not be transferred at all if there are better ones available. When grade 4–5 embryos are to be transferred, the couple should be counselled as regards the poor prognosis.
Blastocyst transfer has been suggested as a means of facilitating higher PR when the number of embryos transferred is limited (Gardner et al., 1998). The implantation rate of 35.8% achieved in our survey, when day 2 embryos at the four-cell stage were transferred, suggests that it may not be necessary to culture the embryos to the blastocyst stage in order to obtain acceptable implantation rates. It has been suggested that a delay in embryo transfer from 48 to 72 h after oocyte retrieval improves the clinical outcome in IVF (Carrillo et al., 1998). In the few day 3 transfers carried out in our programme, we achieved an implantation rate of 45.5% with embryos at the six- to eight-cell stage. There may also be more sophisticated methods to judge embryo quality in future. Attention has to be paid, however, to the quality of the laboratory processes and culture media, to ensure the best possible outcome (Murdoch et al., 1998).
If only one embryo was available, the PR did not relate to the age of the woman in our study. Young women from whom only one embryo can be obtained appear to be a group with overall poor prognosis. In elective one-embryo transfers, the PR per embryo transfer was higher in women younger than 36 years, which is in agreement with many earlier reports (Roseboom et al., 1995; Coetsier and Dhont, 1998). It might be considered that two embryos could be transferred in older women (Hull et al., 1996; Adonakis et al., 1997; Elsner et al., 1997). In addition, the number of oocytes retrieved and the proportion of fertilized oocytes at the first attempt can be used as prognostic factors (Bouckaert et al., 1994) when adopting guidelines on selecting subjects for elective one-embryo transfer. The chances of a live birth are related to the number of fertilized oocytes because of the greater selection of embryos available for transfer (Templeton and Morris, 1998).
Good cryopreservation and thawing techniques are necessary when elective single embryo transfers are being carried out (Horne et al., 1997). In our clinic, we have cryopreserved all grade 1–3 embryos, and satisfactory pregnancy rates of 14.3% per single frozen–thawed embryo transfer and 17.9% per double frozen–thawed embryo transfer were obtained. After transfers of two frozen–thawed embryos, two out of seven pregnancies were twin. This means that transfer of only one embryo should also be considered in selected cases after cryopreservation.
To avoid the complications of twin pregnancies in assisted reproductive technology programmes, transfer of only one embryo at a time is highly recommended, at least among younger subjects, and during the first two to three treatment cycles. A prospective randomized study would be useful to compare the outcome of elective one- and two-embryo transfers, and to identify the group of subjects suitable for elective one-embryo transfer.
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Notes |
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4 To whom correspondence should be addressed
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Submitted on February 15, 1999; accepted on May 27, 1999.
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S. Bhattacharya and A. Templeton What is the most relevant standard of success in assisted reproduction?: Redefining success in the context of elective single embryo transfer: evidence, intuition and financial reality Hum. Reprod., September 1, 2004; 19(9): 1939 - 1942. [Abstract] [Full Text] [PDF]
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U.B. Wennerholm and C. Bergh What is the most relevant standard of success in assisted reproduction?: Singleton live births should also include preterm births Hum. Reprod., September 1, 2004; 19(9): 1943 - 1945. [Abstract] [Full Text] [PDF]
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A. P.A. Van Montfoort, J. C.M. Dumoulin, A. D.M. Kester, and J. L.H. Evers Early cleavage is a valuable addition to existing embryo selection parameters: a study using single embryo transfers Hum. Reprod., September 1, 2004; 19(9): 2103 - 2108. [Abstract] [Full Text] [PDF]
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H. Martikainen, M. Orava, J. Lakkakorpi, and L. Tuomivaara Day 2 elective single embryo transfer in clinical practice: better outcome in ICSI cycles Hum. Reprod., June 1, 2004; 19(6): 1364 - 1366. [Abstract] [Full Text] [PDF]
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W. Buckett and S. L. Tan What is the most relevant standard of success in assisted reproduction?: The importance of informed choice Hum. Reprod., May 1, 2004; 19(5): 1043 - 1045. [Abstract] [Full Text] [PDF]
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J. Gerris, P. De Sutter, D. De Neubourg, E. Van Royen, J. Vander Elst, K. Mangelschots, M. Vercruyssen, P. Kok, M. Elseviers, L. Annemans, et al. A real-life prospective health economic study of elective single embryo transfer versus two-embryo transfer in first IVF/ICSI cycles Hum. Reprod., April 1, 2004; 19(4): 917 - 923. [Abstract] [Full Text] [PDF]
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V. Soderstrom-Anttila, S. Vilska, S. Makinen, T. Foudila, and A.-M. Suikkari Elective single embryo transfer yields good delivery rates in oocyte donation Hum. Reprod., September 1, 2003; 18(9): 1858 - 1863. [Abstract] [Full Text] [PDF]
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P. Tummers, P. D. Sutter, and M. Dhont Risk of spontaneous abortion in singleton and twin pregnancies after IVF/ICSI Hum. Reprod., August 1, 2003; 18(8): 1720 - 1723. [Abstract] [Full Text] [PDF]
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A. Vahratian, L. A. Schieve, M. A. Reynolds, and G. Jeng Live-birth rates and multiple-birth risk of assisted reproductive technology pregnancies conceived using thawed embryos, USA 1999-2000 Hum. Reprod., July 1, 2003; 18(7): 1442 - 1448. [Abstract] [Full Text] [PDF]
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A. Tiitinen, L. Unkila-Kallio, M. Halttunen, and C. Hyden-Granskog Impact of elective single embryo transfer on the twin pregnancy rate Hum. Reprod., July 1, 2003; 18(7): 1449 - 1453. [Abstract] [Full Text] [PDF]
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A. Salumets, C. Hyden-Granskog, S. Makinen, A.-M. Suikkari, A. Tiitinen, and T. Tuuri Early cleavage predicts the viability of human embryos in elective single embryo transfer procedures Hum. Reprod., April 1, 2003; 18(4): 821 - 825. [Abstract] [Full Text] [PDF]
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J.A. Land and J.L.H. Evers Risks and complications in assisted reproduction techniques: Report of an ESHRE consensus meeting Hum. Reprod., February 1, 2003; 18(2): 455 - 457. [Abstract] [Full Text] [PDF]
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R. D. Lambert Safety issues in assisted reproduction technology: The children of assisted reproduction confront the responsible conduct of assisted reproductive technologies Hum. Reprod., December 1, 2002; 17(12): 3011 - 3015. [Abstract] [Full Text] [PDF]
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P. De Sutter, J. Gerris, and M. Dhont A health-economic decision-analytic model comparing double with single embryo transfer in IVF/ICSI Hum. Reprod., November 1, 2002; 17(11): 2891 - 2896. [Abstract] [Full Text] [PDF]
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D.D. Neubourg, K. Mangelschots, E. Van Royen, M. Vercruyssen, G. Ryckaert, M. Valkenburg, J. Barudy-Vasquez, and J. Gerris Impact of patients' choice for single embryo transfer of a top quality embryo versus double embryo transfer in the first IVF/ICSI cycle Hum. Reprod., October 1, 2002; 17(10): 2621 - 2625. [Abstract] [Full Text] [PDF]
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J. Gerris, D. De Neubourg, K. Mangelschots, E. Van Royen, M. Vercruyssen, J. Barudy-Vasquez, M. Valkenburg, and G. Ryckaert Elective single day 3 embryo transfer halves the twinning rate without decrease in the ongoing pregnancy rate of an IVF/ICSI programme Hum. Reprod., October 1, 2002; 17(10): 2626 - 2631. [Abstract] [Full Text] [PDF]
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F. Guerif, F. Fourquet, H. Marret, M.-H. Saussereau, C. Barthelemy, C. Lecomte, P. Lecomte, J. Lansac, and D. Royere Cohort follow-up of couples with primary infertility in an ART programme using frozen donor semen Hum. Reprod., June 1, 2002; 17(6): 1525 - 1531. [Abstract] [Full Text] [PDF]
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L. Engmann, N. Maconochie, S. L. Tan, and J. Bekir Trends in the incidence of births and multiple births and the factors that determine the probability of multiple birth after IVF treatment Hum. Reprod., December 1, 2001; 16(12): 2598 - 2605. [Abstract] [Full Text] [PDF]
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 M. A. Reynolds, L. A. Schieve, G. Jeng, H. B. Peterson, and L. S. Wilcox Risk of Multiple Birth Associated with In Vitro Fertilization using Donor Eggs Am. J. Epidemiol., December 1, 2001; 154(11): 1043 - 1050. [Abstract] [Full Text] [PDF]
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V. Vlaisavljevic, B. Kovacic, M. Reljic, V. G. Lovrec, and M. C. Sajko Is there any benefit from the culture of a single oocyte to a blastocyst-stage embryo in unstimulated cycles? Hum. Reprod., November 1, 2001; 16(11): 2379 - 2383. [Abstract] [Full Text] [PDF]
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A. Salumets, C. Hyden-Granskog, A.-M. Suikkari, A. Tiitinen, and T. Tuuri The predictive value of pronuclear morphology of zygotes in the assessment of human embryo quality Hum. Reprod., October 1, 2001; 16(10): 2177 - 2181. [Abstract] [Full Text] [PDF]
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H. Martikainen, A. Tiitinen, C. Tomas, J. Tapanainen, M. Orava, L. Tuomivaara, S. Vilska, C. Hyden-Granskog, and O. Hovatta One versus two embryo transfer after IVF and ICSI: a randomized study Hum. Reprod., September 1, 2001; 16(9): 1900 - 1903. [Abstract] [Full Text] [PDF]
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O. Ozturk, S. Bhattacharya, and A. Templeton Avoiding multiple pregnancies in ART: Evaluation and implementation of new strategies Hum. Reprod., July 1, 2001; 16(7): 1319 - 1321. [Abstract] [Full Text] [PDF]
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A. Tiitinen, M. Halttunen, P. Harkki, P. Vuoristo, and C. Hyden-Granskog Elective single embryo transfer: the value of cryopreservation Hum. Reprod., June 1, 2001; 16(6): 1140 - 1144. [Abstract] [Full Text] [PDF]
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ESHRE Campus Course Report Prevention of twin pregnancies after IVF/ICSI by single embryo transfer Hum. Reprod., April 1, 2001; 16(4): 790 - 800. [Abstract] [Full Text] [PDF]
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A. Strandell, C. Bergh, and K. Lundin Selection of patients suitable for one-embryo transfer may reduce the rate of multiple births by half without impairment of overall birth rates Hum. Reprod., December 1, 2000; 15(12): 2520 - 2525. [Abstract] [Full Text] [PDF]
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C. Wittemer, K. Bettahar-Lebugle, J. Ohl, C. Rongieres, I. Nisand, and P. Gerlinger Zygote evaluation: an efficient tool for embryo selection Hum. Reprod., December 1, 2000; 15(12): 2591 - 2597. [Abstract] [Full Text] [PDF]
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J. Gerris and E. Van Royen Avoiding multiple pregnancies in ART: A plea for single embryo transfer Hum. Reprod., September 1, 2000; 15(9): 1884 - 1888. [Abstract] [Full Text] [PDF]
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A. Templeton Avoiding multiple pregnancies in ART: Replace as many embryos as you like--one at a time Hum. Reprod., August 1, 2000; 15(8): 1662 - 1662. [Full Text] [PDF]
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T. E. C. Workshop Group Multiple gestation pregnancy Hum. Reprod., August 1, 2000; 15(8): 1856 - 1864. [Abstract] [Full Text] [PDF]
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 A. G SUTCLIFFE Intracytoplasmic sperm injection and other aspects of new reproductive technologies Arch. Dis. Child., August 1, 2000; 83(2): 98 - 101. [Full Text] [PDF]
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J. Hazekamp, C. Bergh, U.-B. Wennerholm, O. Hovatta, P.O. Karlstrom, and A. Selbing Avoiding multiple pregnancies in ART: Consideration of new strategies Hum. Reprod., June 1, 2000; 15(6): 1217 - 1219. [Abstract] [Full Text] [PDF]
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J. Tesarik, A.M. Junca, A. Hazout, F.X. Aubriot, C. Nathan, P. Cohen-Bacrie, and M. Dumont-Hassan Embryos with high implantation potential after intracytoplasmic sperm injection can be recognized by a simple, non-invasive examination of pronuclear morphology Hum. Reprod., June 1, 2000; 15(6): 1396 - 1399. [Abstract] [Full Text] [PDF]
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