A Multi-Center Cohort Study on the Impact of Maternal Age on Chromosomal Mosaicism in Trophectoderm Biopsies

International Journal of Obstetrics and Gynecology | Vol. 14, No. 8, August 2026 | pp. 471–482

DOI: 10.46882/2026/IJOG/000520

Original Research Article

Title: A Multi-Center Cohort Study on the Impact of Maternal Age on Chromosomal Mosaicism in Trophectoderm Biopsies

Names of Authors: Mariam T. Bello¹, Grace E. Effiong²

Authors’ Affiliations:
¹ Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, University College Hospital, Ibadan, Nigeria
² Department of Public Health, University of Calabar, Calabar, Nigeria

Abstract:
Embryonic chromosomal mosaicism poses a major interpretive challenge during preimplantation genetic testing for aneuploidies (PGT-A). This multi-center prospective cohort study investigated whether advanced maternal age correlates with an increased prevalence of chromosomal mosaicism within trophectoderm biopsies. A database of 2,400 blastocysts undergoing trophectoderm biopsy across three IVF laboratories was analyzed utilizing high-resolution next-generation sequencing (NGS). Blastocysts were classified as euploid, aneuploid, or mosaic (defined as containing 20% to 50% abnormal cell lines). Results were stratified across four maternal age brackets: < 35 years (n = 800), 35 to 37 years (n = 650), 38 to 40 years (n = 550), and > 40 years (n = 400). While the absolute incidence of full aneuploidy increased linearly with maternal age (p < 0.001), the proportion of mosaic blastocysts remained remarkably stable across all cohorts: 14.2% in < 35 years, 15.1% in 35 to 37 years, 13.8% in 38 to 40 years, and 14.5% in > 40 years (p = 0.84). Multi-variate logistic regression confirmed that maternal age was not an independent predictor of trophectoderm mosaicism (Odds Ratio = 1.02; 95% CI, 0.94 to 1.11, p = 0.68). In contrast, specific controlled ovarian hyperstimulation parameters and embryology laboratory conditions significantly influenced mosaicism rates (p = 0.012). Unlike complete meiotic aneuploidies, mitotic chromosomal mosaicism in trophectoderm cells occurs independently of maternal age, highlighting the influence of post-zygotic replication mechanics rather than oocyte aging.

Keywords: Preimplantation Genetic Testing; Chromosomal Mosaicism; Trophectoderm Biopsy; Advanced Maternal Age; Next-Generation Sequencing; Aneuploidy.

Manuscript Timeline: Received: May 25, 2026; Revised: July 12, 2026; Accepted: July 30, 2026; Published: August 16, 2026.

Citation: Bello MT, Effiong GE. A Multi-Center Cohort Study on the Impact of Maternal Age on Chromosomal Mosaicism in Trophectoderm Biopsies. International Journal of Obstetrics and Gynecology. 2026; 14(8): 471–482.

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