Cumulative live birth rates following blastocyst- versus cleavage-stage embryo transfer in the first complete cycle of IVF: a population-based retrospective cohort study

N. J. Cameron, S. Bhattacharya, D. J. McLernon* (Corresponding Author)

*Corresponding author for this work

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Abstract

STUDY QUESTION: Is there a difference in the odds of a live birth following blastocyst- versus cleavage-stage embryo transfer in the first complete cycle of IVF?
SUMMARY ANSWER: After adjusting for indication bias, there was not enough evidence to suggest a difference in the odds of live birth following blastocyst- versus cleavage-stage embryo transfer in the first complete cycle of IVF.
WHAT IS KNOWN ALREADY: Replacement of blastocyst-stage embryos has become the dominant practice in IVF but there is uncertainty about whether this technique offers an improved chance of cumulative live birth over all fresh and frozen-thawed embryo transfer attempts associated with a single oocyte retrieval.
STUDY DESIGN, SIZE, DURATION: National population-based retrospective cohort study of 100 610 couples who began their first IVF/ICSI treatment at a licenced UK clinic between 1 January 1999 and 30 July 2010.
PARTICIPANTS/MATERIALS, SETTING, METHODS: Data from the Human Fertilisation and Embryology Authority (HFEA) register on IVF/ICSI treatments using autologous gametes between 1999 and 2010 were analysed. The primary outcome was the live birth rate over the first complete cycle of IVF. Cumulative live birth rates (CLBR) were compared for couples who underwent blastocyst
and cleavage transfer, and the adjusted odds of live birth over the first complete cycle were estimated for each group using binary logistic regression. This analysis was repeated within groups of female age, oocytes collected and primary versus secondary infertility. Inverse probability of treatment weighting was used to account for the imbalance in couple characteristics between treatment groups.
MAIN RESULTS AND THE ROLE OF CHANCE: In total, 94 294 (93.7%) couples had a cleavage-stage embryo transfer while 6316 (6.3%) received blastocysts. Over the first complete cycle of IVF/ICSI (incorporating all fresh and frozen-thawed embryo transfers associated with the first oocyte retrieval), the CLBR was increased in those who underwent blastocyst transfer (56.5%) compared
to cleavage-stage embryo transfer (34.8%). However, after accounting for the imbalance between exposures, blastocyst transfer did not significantly influence the odds of live birth over the first complete cycle (adjusted odds ratio: 1.03 (0.96, 1.10)). LIMITATIONS, REASONS FOR CAUTION: Limitations of our study include the retrospective nature of the HFEA dataset and availability of linked data up until 2010. We were unable to adjust for some confounders, such as smoking status, BMI and embryo quality, as these data are not collected at national level by the HFEA. Similarly, there may be unknown couple, treatment or clinic variables that may influence our results. We were unable to assess the intended stage of embryo transfer for women who did not have an embryo
replaced, and therefore excluded them from our study. Perinatal outcomes were not included in our analyses and would be a useful basis for future study
Original languageEnglish
Pages (from-to)2365-2374
Number of pages10
JournalHuman Reproduction
Volume35
Issue number10
Early online date19 Sept 2020
DOIs
Publication statusPublished - Oct 2020

Bibliographical note

Acknowledgements:
We thank the Human Fertilisation and Embryological Authority for permission to analyse their database, extracting the requested information and assisting with our queries in an efficient manner. We acknowledge the data management support of the Grampian Data Safe Haven (DaSH) and the associated financial support of NHS Research Scotland, through NHS Grampian investment in the Grampian DaSH. For more information, visit the DaSH website http://www.abdn.ac.uk/iahs/facilities/grampian-data-safe-haven.php.
Funding:
N.J.C. received a Wolfson Foundation Intercalated Degree Research Fellowship funded by the Wolfson Foundation, through the Royal College of Physicians. This work was supported by a Chief Scientist Office postdoctoral training fellowship in health services research and health of the public research (ref PDF/12/06). The views expressed here are those of the authors and not necessarily those of the Chief Scientist Office. The funders had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; preparation, review or approval of the manuscript; or decision to submit the manuscript for publication.

Keywords

  • blastocyst
  • cleavage-stage embryo
  • cumulative live birth rate
  • IVF
  • embryo transfer
  • indication bias
  • Embryo transfer
  • Blastocyst
  • Cumulative live birth rate
  • Indication bias
  • Cleavage-stage embryo

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