Girl or boy? Is the speed of embryo development influential?

The ASEBIR conference concluded yesterday, in which we presented this retrospective study among 11 research projects, some in collaboration with the University of Alicante Reproductive Medicine Chair. This study evaluated whether the speed of embryo development influences the sex of newborns from assisted reproduction techniques using either the couples’ own oocytes or donated oocytes. The obtained results showed that male embryos (XY) develop faster than the female embryos (XX), which means that at the time of transfer, when performed on day 5, the male embryos are found to be in a more advanced stage of development. These embryos are categorized as superior according to the current classifications and therefore are the candidates to be transferred and implanted. This suggests that with a day 5 transfer, we could be generating a positive bias in favor of males. However, we have not observed differences in the sex-ratios of transfers on day 5 (1.07) compared to the general world population (1.07), according to the latest CIA World Factbook record.

 

RELATIONSHIP BETWEEN THE SPEED OF EMBRYO DEVELOPMENT AND SEX OF THE  OFFSPRING AFTER ART. J. Ten, A. Sáez, B. Moliner, J. Guerrero, J. Llácer, J. de Juan, R. Bernabeu 

See the “research and development” section