The impact of preimplantation genetic testing for aneuploidy on prenatal screening

Prenatal screening after preimplantation genetic testing for aneuploidy: time to evaluate old strategies

RESEARCH QUESTION

How does first-trimester aneuploidy screening perform in pregnancies achieved through IVF with preimplantation genetic testing for aneuploidy (PGT-A) in a medical setting?

DESIGN

This retrospective cohort study was undertaken in a single tertiary care centre between January 2013 and June 2022. In total, 20,237 women had prenatal follow-up at the study centre and were included in the study. The women were divided into three groups: singleton pregnancies conceived through the transfer of a PGT-A-screened euploid embryo (n = 510); singleton pregnancies conceived through IVF without PGT-A (n = 3291); and singleton pregnancies conceived naturally (n = 16,436).

RESULTS

The conventional combined screening test for pregnancies conceived through IVF with PGT-A had specificity of 91%; sensitivity could not be calculated as there were no cases of fetal aneuploidy in this group. In 89.1% of pregnancies conceived through IVF with PGT-A with high risk for trisomy 21, 18 or 13, the result was related to advanced maternal age (>35 years at time of screening).

CONCLUSIONS

The current screening strategy for trisomies 21, 18 and 13 can generate unnecessary tests in pregnancies achieved through IVF with PGT-A. A new protocol is needed for these patients, with greater weight given to ultrasound markers.

Challenges experienced by genetic counselors while they provided counseling about mosaic embryos

Objective

To survey genetic counselors (GCs) who have counseled about mosaic embryos regarding the challenges they faced in counseling this patient population and assess their need for more resources to support their practice.

Design

Self-administered online survey.

Setting

Academic university.

Study Population

Seventy-eight GCs primarily from the United States and Canada.

Interventions

Genetic counselors completed a quantitative survey with an embedded qualitative component. Quantitative data were analyzed by descriptive statistics. An inductive thematic analysis was performed on open-text responses.

Main Outcome Measures

Genetic counselors were asked what clinical activities relating to mosaic embryos they performed. They were then asked to rate how challenging each activity was to perform using a 5-point scale; a rating of 4 or 5 was defined as highly challenging. Open-text questions enabled GCs to describe factors that they felt contributed to these challenges.

Results

The challenges reported by GCs included the uncertainty of outcomes in offspring after mosaic embryo transfer, limited guidelines available to assist clinicians with counseling about mosaic embryos, and ranking mosaic embryos by suitability for transfer. The contributing factors suggested by participants included limited outcome data, limited GC involvement in pretest counseling for preimplantation genetic testing for aneuploidy (PGT-A), and perceived inconsistency in counseling practices across clinics. Genetic counselors differed in their genetic testing recommendations for pregnancies conceived after mosaic embryo transfer. Amniocentesis and postnatal assessment were recommended by 85% and 49% of GCs, respectively, and 15% recommended chorionic villus sampling and noninvasive prenatal testing. Almost all (92%) reported a need for more resources, such as standardized guidelines, more outcome data, and continuing education on PGT-A and mosaicism.

Conclusions

This study describes challenges experienced by GCs while they counseled about mosaic embryos. Our findings demonstrate a need for more outcome data on mosaic embryo pregnancies and for evidence-based clinical guidelines. The differing recommendations for prenatal genetic testing among GCs in the study warrant further research into contributing factors. We strongly recommend that pretest counseling, including a discussion regarding mosaicism, is provided to all couples considering PGT-A to reduce counseling challenges and to promote patients' informed decision-making.