THE EFFICACY OF PREIMPLANTATION GENETIC TESTING FOR ANEUPLOIDY (PGT-A) IN IMPROVING CLINICAL PREGNANCY RATES

Abstract

Abstract. Preimplantation genetic testing for aneuploidy (PGT-A) has become 
an  integral  part  of  assisted  reproductive  technologies  (ART)  aimed  at  improving 
clinical pregnancy rates by selecting genetically viable embryos for transfer. Among 
the most common methods of PGT-A are fluorescence in situ hybridization (FISH) and 
next-generation sequencing (NGS), each with distinct advantages and limitations. This 
thesis investigates and compares the clinical outcomes of these methods, particularly 
focusing on clinical pregnancy rates and the proportion of euploid embryos, in women 
of varying reproductive age. Recent studies have shown that while both methods serve 
to increase clinical pregnancy rates, NGS/SNP has demonstrated superior efficacy in 
identifying a wider array of chromosomal abnormalities, leading to better outcomes, 
particularly for women of advanced maternal age. The ability of NGS/SNP to detect a 
broader spectrum of chromosomal issues, including microdeletions and translocations, 
makes  it  more  accurate  in  selecting  genetically  healthy  embryos  for  transfer.  In 
contrast, FISH, despite its advantages in detecting certain chromosomal abnormalities, 
has a narrower range of detection, often missing more complex aneuploidies, especially 
in  older  women.  In  clinical  studies,  NGS/SNP  has  been  shown  to  result  in  higher 
clinical  pregnancy  rates  compared  to  FISH.  For  instance,  a  study  by  Munné  et  al. 
(2018)  demonstrated  that  NGS/SNP  improved  clinical  outcomes  significantly  for 
women over 35 years, achieving a pregnancy rate of 66.67% compared to 40% with 
FISH (Munné et al., 2018). Furthermore, NGS/SNP's higher sensitivity enables more 
accurate identification of euploid embryos, which is crucial for improving pregnancy 
success rates. Although NGS/SNP is more expensive and requires a longer processing 
time  compared  to  FISH,  its  ability  to  detect  a  broader  range  of  chromosomal 
abnormalities offers a more reliable and comprehensive approach to embryo selection. 
As  a  result,  NGS/SNP  is  increasingly  becoming  the  method  of  choice  in  ART, 
particularly  for  women  with  advanced  maternal  age  who  face  a  higher  risk  of 
chromosomal abnormalities and miscarriage.