Preimplantation Genetic Diagnosis (PGD) for Monogenic Disorders: the Value of Concurrent Aneuploidy Screening

Abstract

Pre-implantation genetic diagnosis (PGD) has changed the landscape of clinical genetics by helping families reduce the transmission of monogenic disorders. However, given the high prevalence of embryonic aneuploidy, particularly in patients of advanced reproductive age, unaffected embryos remain at high risk of implantation failure or pregnancy loss due to aneuploidy. 24-chromosome aneuploidy screening has become widely utilized in routine in vitro fertilization (IVF) to pre-select embryos with greater pregnancy potential, but concurrent 24-chromosome aneuploidy screening has not become standard practice in embryos biopsied for PGD. We performed a retrospective cohort study of patients who underwent PGD with or without 24-chromosome aneuploidy screening to explore the value of concurrent screening. Among the PGD+aneuploidy-screened group (n=355 blastocysts), only 25.6% of embryos were both Single Gene Disorder (SGD)-negative (or carriers) and euploid; thus the majority of embryos were ineligible for transfer due to the high prevalence of aneuploidy. Despite a young mean age (32.4±5.9y), 49.9% of Blastocysts were aneuploid. The majority of patients (53.2%) had ≥1 blastocyst that was Single Gene Disorder (SGD)-unaffected but aneuploid; without screening, these unaffected but aneuploid embryos would likely have been transferred resulting in implantation failure, pregnancy loss, or a pregnancyaffected by chromosomal aneuploidy. Despite the transfer of nearly half the number of embryos in the aneuploidy-screened group (1.1±0.3 vs. 1.9±0.6, p<0.0001), the implantation rate was higher (75% vs. 53.3%) and miscarriage rate lower (20% vs. 40%) (although not statistically significant). 24-chromosome aneuploidy screening when performed concurrently with PGD provides valuable information for embryo selection, and notably improves single embryo transfer rates.