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Q&A

Genetics

Poster Session 2

(523) Fetal and Neonatal Outcomes after “Atypical Finding for Sex Chromosomes” on Cell-Free Fetal DNA Screening

Tuesday, February 13, 2024

3:30 PM – 5:00 PM

Location: Prince George's Exhibit Hall CDE, Lower Atrium Level

Primary & Presenting Author(s)

Jenny Y. Mei, MD (she/her/hers)

Maternal-Fetal Medicine Fellow
University of California, Los Angeles
Los Angeles, CA, United States

Coauthor(s)

AM

Aparna Murali, MS

Genetic Counselor, Division of Clinical Genetics, Department of Human Genetics
David Geffen School of Medicine, University of California Los Angeles
Los Angeles, CA, United States
AN

Alexa Nitka, MS

Genetic Counselor, Division of Clinical Genetics, Department of Human Genetics
David Geffen School of Medicine, University of California Los Angeles
Los Angeles, CA, United States
SK

Sung-Hae Kang, PhD

Associate Professor, Department of Pathology and Laboratory Medicine
David Geffen School of Medicine, University of California Los Angeles
Los Angeles, CA, United States
SS

Sulagna Saitta, MD, PhD

Clinical Professor, Division of Clinical Genetics, Department of Human Genetics
David Geffen School of Medicine, University of California Los Angeles
Los Angeles, CA, United States
Christina S. Han, MD (she/her/hers)

Associate Clinical Professor
David Geffen School of Medicine at UCLA
Los Angeles, CA, United States

Objective: Prenatal cell-free fetal DNA (cfDNA) screening is primarily used to identify pregnancies at risk for common autosomal trisomies (CAT). Common cfDNA results include low risk (LR) or high risk (HR) for CAT or sex chromosomal aneuploidies (SCA), and low fetal fraction (FF). In 2020, a new report output was noted on a common cfDNA platform, labeled “atypical finding for sex chromosomes” (AFSC), stratified as “no result for all” (AFSC-NR), “LR for other conditions, no fetal sex” (AFSC-LR), or “LR for other conditions, XX sex” (AFSC-LR-XX). We aim to identify the outcomes of AFSC results on cfDNA.

Study Design:

We performed a retrospective cohort study of AFSC results at a single referral center from 01/2020-12/2022. Exclusion criteria included HR for CAT/SCA, low FF, & AFSC of suspected maternal origin. All AFSC patients were offered diagnostic testing, or if declined, neonatal phenotyping. Maternal demographic and outcome data were abstracted from medical records. Independent sample t-test, ANOVA, Chi-square, and multinomial logistic regression were used to compare outcomes between groups as indicated.

Results:

Of 5050 cfDNA samples (4931 singletons; 118 twins), 38 (0.008%) patients with 43 fetuses (5 twins) yielded AFSC outputs: 17 (39.5%) AFSC-NR, 11 (25.6%) AFSC-LR, and 15 (34.9%) AFSC-LR-XX. Genetic testing overview and results are listed in Figure 1. Compared to AFSC-NR, AFSC-LR were more likely to have higher rate of genetic testing (p=0.008), abnormal diagnostic testing (p=0.033), lower gestational age at lab draw (p=0.035), lower rate of twins (p=0.021), and higher likelihood of a female fetus (p=0.034). AFSC-NR had higher likelihood of preterm birth (p=0.013) and NICU admission (p=0.03). After controlling for twins, these findings lost significance.

Conclusion:

Incidence of AFSC on cfDNA screening is low. Majority of cases result in normal genetic testing or neonatal phenotype. AFSC-LR is associated with abnormal results on karyotype or microarray. In this limited cohort, maternal & neonatal outcomes are overall reassuring.