The frequency of chromosomal euploidy among 3pN embryos

Background: The evaluation of embryo morphology is one of the most important parameters used to evaluate developmental timing, also providing an indication of chromosomal failure or degeneration. The first step in the evaluation of a fertilization event is determining the number and shape of the pronuclei (PN). Normally fertilized eggs possess two even PN. However, some embryos which develop from abnormally fertilized zygotes may be tri-pronuclear zygotes (3PN). Methods: Thirty embryos were collected from 12 women who underwent in vitro fertilization (IVF) at Dr. Cipto Mangunkusumo General Hospital in Jakarta, Indonesia. Embryos were cultured until the blastocyst stage on days 5-6. The blastomere biopsy was performed by piercing the zona pellucida with a laser under a microscope. Chromosomal numerical abnormalities were analyzed using Next Generation Sequencing (NGS). Results: Among the 30 embryos with 3PN zygotes, 33.3% had a normal chromosomal array, with 22 pairs of autosomes and 2 pairs of sex chromosomes. While the rest of sample population detected as abnormal chromosome (66.7%), with the highest percentage of abnormality was triploidy 43.3%, followed by mosaicism 13.4% and aneuploidy 10%. Conclusion: This was a preliminary study revealed not all morphologically 3PN embryos are genetically abnormal.