Is there a relationship between time-lapse parameters and embryo sex

An analysis of embryo sex by means of time-lapse monitoring identified different cleavage timings. The sex ratio could be affected by the embryo selection method for transfer based on kinetic parameters.

Fernando Bronet, Ph.D., María-Carmen Nogales, Ph.D., Eva Martínez, Ph.D., Marta Ariza, Ph.D., Carmen Rubio, Ph.D., Juan-Antonio García-Velasco, M.D., Ph.D., Marcos Meseguer, Ph.D.

Volume 103, Issue 2, Pages 396-401


To study if it is possible to identify embryo sex from embryo cleavage timings.

Retrospective and observational study.

University-affiliated private fertility center.

Women undergoing preimplantion genetic diagnosis.

All biopsied embryos were cultured in an Embryoscope incubator with time-lapse technology.

Main Outcome Measure(s):
Cleavage timing from insemination to day 3 and all kinetic parameters that have been described in previous studies by our group.

The study included 421 embryos from our Compressive Chromosome Screening program, conducted from January 2012 to December 2012. Embryos were grouped according to their sex: male (176 embryos) and female (161 embryos). Chromosomal abnormal rate was similar for the two groups (male 62.5%, female 58.4%). When morphokinetic parameters were separated in different quartiles and grouped, we found statistical differences between male or female embryos. By logistic regression analysis we found that two specific kinetic variables were relevant: second synchrony (>2 hours) and timing of morula formation (80.8–90.9 hours). With the use of these parameters, we propose an algorithm with four different categories reflecting the range from 71% to 42% in the likelihood of an embryo being female.

Embryo development was affected by embryo sex, and the sex ratio could be affected by the embryo selection method for transfer based on kinetic parameters.

  • Jason M. Franasiak

    Congratulations on an interesting manuscript and model. For patient counseling purposes, would this need to be stated up front this algorithm would result in a significant advantage for sex selection (beyond the 50/50 at baseline) in only a small subset of patients who fell into Category A? Is this something that is being used in clinical settings and if so how is the counseling done a priori? Many thanks.

    • Fernando Bronet

      Thanks for the comments Dr Franasiak. At this moment the Spanish law does not allow sex selection for social reasons, so we are not using the algorithm in order to choose the embryo gender. We now know that there are some differences in cleavage timing depending on the sex of the embryo. However, the algorithm can be used in countries where the law allows sex selection

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