Retrospective cohort analysis on couples seeking pre-implantation genetic testing over a 5-year period

Abstract

Background: Preimplantation genetic testing (PGT) is a method that allows screening of embryos for genetic diseases or chromosomal disorders during assisted reproduction cycles. It serves as an alternative to prenatal diagnosis for at-risk couples by offering early detection and selection of unaffected embryos prior to embryo transfer into the uterus. PGT is classified into three types: PGT for aneuploidy screening (PGT-A), PGT for monogenic diseases (PGT-M) and PGT for structural rearrangements (PGT-SR). With increasing acceptance and utility of PGT in recent years, this study aims to review the usage of PGT in Queen Mary Hospital, Hong Kong. Methods: This is a single-centred, retrospective review on the usage of PGT in Hong Kong over the past 5 years. PGT cases performed in HKU-QMH Centre of Assisted Reproduction and Embryology (HKU-QMH CARE) from January 2015 to September 2020 were collected. The indication for PGT, type of PGT requested, anticipated reproductive risks, and demographics are collected for analysis. Results: A total of 411 couples requested PGT during the study period. The mean age of women was 34.3 years old (range from 21 to 43). 291 couples (71%) requested for PGT due to known genetic diseases risk: 192 couples (47%) requested PGT-M for monogenic disorders, 89 couples (22%) requested PGT-SR for balanced chromosomal changes and 10 couples (2%) requested PGT-A for (mosaic) sex aneuploidy. 120 couples (29%) requested PGT-A because of recurrent pregnancy loss, repeated implantation failure, advanced maternal age and previous abnormal pregnancy. Among the couples requesting PGT-M, 130 couples (68%) were at-risk of passing on an autosomal recessive disease, followed by an autosomal dominant (23%) and an X-linked (9%) condition. Alpha thalassemia is the most common indication for PGT-M (63 couples, 33% of all PGT-M), followed by beta thalassemia (9%). Conclusion: This study reviewed the PGT usage of Hong Kong couples at a single centre over a 5-year period. Thalassemia was the most common monogenic disease for PGT-M. This is consistent with the known genetic spectrum of high carrier rate of thalassemia in Hong Kong.