title: Elective single day 3 embryo transfer halves the twinning rate without decrease in the ongoing pregnancy rate of an IVF/ICSI programme.
abstract: 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.
  
  
  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.
mesh_terms: D000328:Adult; D004624:Embryo Transfer / Q000639:trends; D004622:Embryo, Mammalian / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data; D020554:Sperm Injections, Intracytoplasmic; D014427:Twins