Letters to the editor |
Reply: In unselected patients, elective single embryo transfer prevents all multiples, but results in significantly lower pregnancy rates compared to double embryo transfer
Department of Obstetrics and Gynaecology, Academic Hospital Maastricht, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands
1 To whom correspondence should be addressed. E-mail: avmn{at}sgyn.azm.nl
Sir,
Prof. J. Thompson and Dr M. Lane suggest that we should rephrase our conclusion—‘our study shows that applying elective single embryo transfer (eSET) in the first cycle of an unselected group of patients will lead to a twin pregnancy rate of 0%. The price to be paid is a reduction of the ongoing pregnancy rate to approximately half of that obtained after double embryo transfer (DET). The transfer of only one embryo in a selected group of good prognosis patients leads to a less drastic reduction in pregnancy rate but maintains a twin pregnancy rate of 12.9%’ (van Montfoort et al., 2006
)—to a recommendation that eSET should be adopted only when in the target patient group (either all patients or a specific patient group with a good pregnancy prognosis) the overall implantation rate of embryos is so high that performing DET will lead to only a small increase in pregnancy rate but in a dramatically, and therefore unacceptable, high twin pregnancy rate.
While we thank Prof. J. Thompson and Dr. M. Lane for their suggestion, we think that it is not up to us to make such a general recommendation because this was not the subject of our study. The aim of our study was to analyse what the pregnancy rate would be when the transfer policy is either eSET for all patients or eSET in a selected group of patients and DET in the remaining population. It is up to every infertility centre to decide what their transfer policy will be and what price (in reduction of pregnancy rate) is acceptable for reducing the twin pregnancy rate. As we discussed in our article, whether eSET or DET is preferable depends not only on ongoing pregnancy rates and twin pregnancy rates but also on several other factors such as the health care system (reimbursement of costs) in a particular country and patient preferences.
We think, however, that the reduction in pregnancy rate after eSET in an unselected group of patients does not balance the reduction in twin pregnancy rate. In our clinic, therefore, eSET is applied in a selected group of patients. Our selection is in complete agreement with those suggested by Prof. J. Thompson and Dr M. Lane: eSET will be performed only when our criteria for a good prognosis patient are met, which consist of a patient factor (= ‘r’) contributing to the pregnancy chance (age 37 years or younger) and an embryo quality factor (= ‘e’), i.e. at least one good-quality embryo available. In all eSET studies, selection criteria based on ‘e’ and ‘r’ are used (e.g. Tiitinen et al., 2003; Gerris et al., 2004; Thurin et al., 2004). And as the pregnancy rate after applying DET is always higher as compared with that achieved using eSET, every study group has made an appraisal between the reduction in pregnancy rate and the reduction in twin pregnancy rate after applying eSET instead of DET. We accept Prof. J. Thompson and Dr M. Lane’s suggestion that mathematical models on the relationship between pregnancy and twinning rates with embryonic implantation rate can help to make decisions about which patient group should be treated with eSET or DET. But we think that empirical information on the implantation rate in different patient groups with different embryo qualities is even more important.
When applying our selection criteria, the implantation rate according to the definition of Matorras et al. (2005) (IR = ngestational sacs/ntransferred embryos, where ngestational sacs is the number of gestational sacs observed at vaginal ultrasound 3–5 weeks after transfer and ntransferred embryos the number of transferred embryos) was 45.0% (Table III), with an ongoing pregnancy rate of 33.0% (van Montfoort et al., 2006). This is comparable with the pregnancy rates that have been described for similar selected good-prognosis groups of patients in many other IVF centres, as indicated by Prof. J. Thompson and Dr M. Lane (Gerris et al., 2002; Tiitinen et al., 2003; Martikainen et al., 2004). Besides the data on eSET in a selected group, which are comparable to those of other clinics, we also reported on eSET in an unselected group. In the latter group, we found an implantation rate of 33.1% (Table II) and an ongoing pregnancy rate of 21.4% per embryo transfer. As far as we know, our study is the first to report on pregnancy and implantation rates after eSET in such an unselected group of patients (van Montfoort et al., 2006).
References
Gerris J, De Neubourg D, Mangelschots K, Van Royen E, Vercruyssen M, Barudy-Vasquez J, Valkenburg M, Ryckaert G. (2002) Elective single day 3 embryo transfer halves the twinning rate without decrease in the ongoing pregnancy rate of an IVF/ICSI programme. Hum Reprod 17:2626–2631.
Gerris J, de Sutter P, de Neubourg D, Van Royen E, Vander Elst J, Mangelschots K, Vercruyssen M, Kok P, Elseviers M, Annemans L, et al. (2004) A real-life prospective health economic study of elective single embryo transfer versus two-embryo transfer in first IVF/ICSI cycles. Hum Reprod 19:917–923.
Martikainen H, Orava M, Lakkakorpi J, Tuomivaara L. (2004) Day 2 elective single embryo transfer in clinical practice: better outcome in ICSI cycles. Hum Reprod 19:1364–1366.
Matorras R, Matorras F, Mendoza R, Rodriguez M, Remohi J, Rodriguez-Escudero FJ, Simon C. (2005) The implantation of every embryo facilitates the chances of the remaining embryos to implant in an IVF programme: a mathematical model to predict pregnancy and multiple pregnancy rates. Hum Reprod 20:2923–2931.
van Montfoort AP, Fiddelers AA, Janssen JM, Derhaag JG, Dirksen CD, Dunselman GA, Land JA, Geraedts JP, Evers JL, Dumoulin JC. (2006) In unselected patients, elective single embryo transfer prevents all multiples, but results in significantly lower pregnancy rates compared with double embryo transfer: a randomized controlled trial. Hum Reprod 21:338–343.
Thurin A, Hausken J, Hillensjo T, Jablonowska B, Pinborg A, Strandell A, Bergh C. (2004) Elective single-embryo transfer versus double-embryo transfer in in vitro fertilization. N Engl J Med 351:2392–2402.
Tiitinen A, Unkila-Kallio L, Halttunen M, Hyden-Granskog C. (2003) Impact of elective single embryo transfer on the twin pregnancy rate. Hum Reprod 18:1449–1453.
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