Specific Gravity Device Can Predict Bovine Embryo Sex

ABSTRACT OBJECTIVE: Previous research has demonstrated that a Specific Gravity Device (SGD) is useful in providing a noninvasive means of assessing embryo quality at various stages of development from zygote to blastocyst. Preliminary data suggested the system might also be useful for predicting embryo sex. The objective of the present study was to assess the predictive value of the SGD in determining embryo sex using a bovine model. DESIGN: Lab-based trial of the SGD in predicting embryo sex. MATERIALS AND METHODS: Bovine oocytes were collected from ex vivo ovaries and fertilized in vitro. Six hundred embryos developed into grade 1 or 2 blastocysts and were individually assessed in the SGD. Embryo descent times were measured and recorded in seconds and then used in an Embryo Prediction Algorithm (EPA) to predict embryo sex. The sex of each embryo was also confirmed individually by Polymerase Chain Reaction (PCR) by an independent laboratory. Comparisons were then made between EPA prediction and PCR values to assess the ability of the SGD to predict embryo sex. RESULTS: PCR data were obtained on 463 of the 600 embryos and available for comparison with SGD predictions. The EPA demonstrated significant differences between male and female embryos (P<0.05). Further, the EPA demonstrated 65.3-78.4% accuracy selecting for female embryos. These data suggest, with refinement, the SGD might provide a noninvasive means of predict sex of preimplantation embryos. CONCLUSION: The SGD can detect embryo sex based on differences in embryo buoyancy. Theoretically, the differences in the buoyancy of mammalian blastocyst embryos would be a reflection of differences in the chromosomal weight of X and Y chromosomes or developmental differences of male and female embryos. Data demonstrate a high degree of correlation between SGD and the PCR results suggesting the technology can provide a noninvasive means to differentiate female pre-implantation embryos without the use of pre-implantation genetic testing or sexed semen. On-going studies are assessing if improvements in the EPA will allow predictive values for male embryos as well. Identifying the sex of an embryo is important for family balancing or for patients with a known sex-linked genetic disorder.