Is there an association between oocyte number and embryo quality? A systematic review and meta-analysis

Belinda G. Vermey*, Su Jen Chua, Mohammad Hadi Zafarmand, Rui Wang, Salvatore Longobardi, Evelyn Cottell, Francois Beckers, Ben W. Mol, Christos A. Venetis, Thomas D'Hooghe

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

32 Citations (Scopus)


This systematic review and meta-analysis determined the association between aspirated after ovarian stimulation and top/good quality embryos obtained in women undergoing ovarian stimulation for IVF/intracytoplasmic sperm injection (ICSI). MEDLINE, EMBASE, Scopus, CINAHL and Web of Science were searched for English-language publications on top/good-quality embryos at cleavage (day 2/3) and/or blastocyst (day 5/6) developmental stages, up to 18 November 2017. Twenty-eight studies (three prospective and 25 retrospective) reporting data on 291,752 assisted reproductive technology (ART) cycles were considered eligible. We confirmed a strong positive association between oocytes retrieved and top/good-quality day 2/3 embryos (weighted correlation coefficient [rw] = 0.791), day 5/6 embryos (rw = 0.901), metaphase II oocytes (rw = 0.988), oocytes exhibiting two pronuclei (rw = 0.987) and euploid embryos (rw = 0.851); P < 0.001 for all correlations (evaluated in subsets of the 17 studies). Data from 5657 cycles showed that the group with the most oocytes aspirated had the most top/good-quality day 2/3 embryos (pooled standardized mean differences (high [>15] versus low [<4] 1.91, 95% confidence interval [CI] 1.05–2.77, P < 0.0001; high versus medium [4–15] 1.15, 95% CI 0.74–1.55, P < 0.0001; medium versus low 1.41, 95% CI 0.79–2.03, P < 0.0001). Individual participant meta-analysis would enable accurate determination of these associations and other outcomes.

Original languageEnglish
Pages (from-to)751-763
Number of pages13
JournalReproductive Biomedicine Online
Issue number5
Early online date3 Jul 2019
Publication statusPublished - 7 Nov 2019

Bibliographical note

The investigators would like to thank the following authors and their contributors for providing us with the extra information of the included studies: Hariton et al., 2017, Kahraman et al., 2016, Kan et al., 2017, Kok et al., 2006, Zhou et al., 2017. We would also like to thank the anonymous peer reviewers who provided constructive feedback on the first version of the manuscript. Editorial support was provided by Steven Goodrick of inScience Communications, London, UK. This project was supported and funded by Merck KGaA.


  • Embryo quality
  • Euploid
  • Oocyte number
  • Oocyte yield


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