Fertilization rate as a novel indicator for cumulative live birth rate: a multicenter retrospective cohort study of 9,394 complete in vitro fertilization cycles

The fertilization rate is positively and independently associated with the cumulative live birth rate and therefore may be adopted as a clinical key performance indicator.

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VOLUME 116, ISSUE 3, P766-773


Giulia Scaravelli, M.D., Ph.D., Carlotta Zacà, B.Sc., Paolo Emanuele Levi Setti, M.D., Ph.D., Claudia Livi, M.D., Filippo Maria Ubaldi, M.D., Ph.D., Maria Teresa Villani, M.D., Ermanno Greco, M.D., Maria Elisabetta Coccia, M.D., Alberto Revelli, M.D., Giuseppe Ricci, M.D., Francesco Fusi, M.D., Vincenzo Vigiliano, B.Sc., Roberto De Luca, B.Sc., Simone Bolli, N.D.B.C., Andrea Borini, M.D. 



To appraise the fertilization rate as a predictive factor for cumulative live birth rate (CLBR).


Multicenter retrospective cohort study.


Ten in vitro fertilization clinics, whose data were collected and processed by the assisted reproductive technology (ART) Italian National Registry.


7,968 couples undergoing 9,394 complete intracytoplasmic sperm injection cycles.



Main Outcome Measure(s)

The primary outcome measure was the CLBR in association with the fertilization rate intervals (<65%—group 1; 65%–80%—group 2; and >80%—group 3). Further data stratification was performed on the basis of maternal age (<34, 35–38, and 39–42 years) and number of retrieved oocytes (5–7, 8–10, and > 10 oocytes).


The CLBR was progressively higher in relation to the fertilization rate in groups 1, 2, and 3 (20.1%, 34.7%, and 41.3%, respectively). The number of recovered oocytes, embryo number per cycle, and cumulative pregnancy rate followed the same trend. The decrease in CLBR with increasing maternal age was significantly correlated with the fertilization rate and CLBR in all 3 maternal age groups. Multivariate logistic regression analysis showed fertilization rate as a factor independently associated with CLBR.


The present data indicated a positive association between the fertilization rate and the CLBR, suggesting the predictive clinical relevance of this parameter and its adoption as a key performance indicator.

Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders. 


Go to the profile of Joel Bernstein
3 months ago

Accepting that  number of recovered oocytes, embryo number per cycle, and cumulative pregnancy rate followed the same trend ie are indicators of an increase in the CLB does it follow that one should aim for more oocytes during controlled oocyte stimulation, or are these features merely indicative of an individuals higher natural fertility and are not dependent on the type of stimulation. To put it another way are the CLB rates dependent on the individual's natural fertility at a specific age and not significantly influenced by the degree of COS (controlled ovarian stimulation) and hence would support the concept of low dose COS.