The Impact of Genetic Carrier Screening on PGT Applications within a Fertility Centre in Australia: PGT-M: Carrier Screening and Referral Pathway

Cheryl TSE, Alice WEEKS, Lynn BURMEISTER, Kelli SORBY: No.1 Fertility – Melbourne (Australia)

Preimplantation Genetic Diagnosis International Society held a conference in 2023, one of our Genetic Counselling Team Leaders, Cheryl Tse, spoke about research they conducted between 2019-2021. You can read the full research below. 

Introduction:

Genetic carrier screening is a form of genetic testing that detects whether an individual or couple are carriers of an autosomal recessive and/or X-linked genetic condition. Within a reproductive setting, the purpose of this is to investigate if a reproductive couple has an increased chance of having a biological child with a specific genetic condition.

Public awareness around genetic carrier screening in Australia was propelled by Mackenzie’s Mission, an Australian Government funded initiative that started in 2018 with the aim of providing reproductive genetic carrier screening to up to 10,000 Australian couples who are either planning to have children or are in early pregnancy. Since then, a plethora of companies offering on- and off-shore testing have been established in Australia, the Royal Australian and New Zealand College of Obstetricians and Gynecologists (RANZCOG) advise that couples planning to conceive or in early pregnancy should be offered genetic carrier screening as part of their reproductive planning and care.

There are currently three types of carrier screening panels available. Single condition screening, for one specific inherited disorder, three-condition screening for cystic fibrosis, spinal muscular atrophy, fragile X syndrome; and expanded carrier screening for hundreds of different inherited disorders.

The objective of this study was to investigate the impact of genetic carrier screening on PGT applications within a fertility centre in Australia, by examining PGT-M cases between 2019 – 2021 to ascertain if there was a significant difference between the indications for embryo genetic testing between the group of patients that received an increased combined reproductive risk from carrier screening, and the group of patients who underwent PGT-M for other indications e.g. family or obstetric history of a single gene/X-linked condition.

Material & methods:

This was a retrospective cohort study involving patients who had undergone IVF treatment with PGT-M at No.1 Fertility, a large fertility clinic based in Melbourne Australia.

Data collected between 2019 – 2021 (n=101)

Retrospective cohort study

Two main cohorts defined as PGT-M patients who:

i) Sought testing due to an increased reproductive risk result on genetic carrier screening

ii) Sought testing for other indications (e.g. family or obstetric history) Statistical methodology: Descriptive statistics (measures of variation), Chi-square test for proportions (significance level of P < 0.05)

Results:

The overall number of PGT-M cases has grown in the study timeframe, specifically tripling in number from 2021 (16) to 2022 (53). This volume has coincided with increased awareness and accessibility of expanded carrier screening in the general Australian population, and the development in range of PGT-M testing indications from 2019-2022 will be presented in the final proof.

Conclusions:

Since genetic carrier screening has been more widely available in Australia, the indications for, and applications of PGT-M has shifted significantly to include a myriad of single-gene (monogenic) and X-linked conditions that are not commonly detected in the absence of a previous affected pregnancy or clinically significant family history.

As the technology around genetic carrier screening continue to develop, the landscape of PGT-M will evolve alongside it, prompting wider applications of PGT technology and its utility to patients undergoing IVF.

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