Assessment of Chromosomal Aneuploidy in Day 3 Cleavage-Stage Embryos and Day 5/6 Blastocysts from Indigenous Black Africans

Abstract

The objectives of this study were to examine the prevalence and to characterize the types of chromosomal aberrations of aneuploidy in cleavage-stage Day 3 human embryos and in Day 5/6 human blastocysts in indigenous Black African women aged ≤ 35 and >35 years. Of the 312 oocytes fertilized for Day 3 embryos and 269 for Day 5/6 blastocysts, 230 blastomeres and 122 blastocysts were biopsied respectively and then subjected to genetic analysis using the array CGH and next generation sequencing methods, genotyping to characterize chromosomal error types of aneuploidy across all 24 chromosomes. A total of 562 oocytes with 486 MII oocytes, were fertilized from which 230 Day 3 embryos and 122 Day 5/6 blastocysts were biopsied. Euploidy rates in Day 3 embryo group and in Day 5/6 blastocyst group were 24.3% and 75.0% respectively while aneuploidy rates were 75.7% and 25.0% respectively. Women aged ≤ 35 years were approximately thrice as likely to have euploid Day 3 embryos (Fisher’s χ²=1.18, p-value=0.29, OR=2.79, 95% CI: 0.61, 12.67). Blastocyst stage biopsy was more efficient in PGS. Blastocyst culture had some level of aneuploidy selection. Higher diagnosis rate was observed as there was lower rate of embryos with no diagnosis.