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Q&A

Genetics

Poster Session 3

(766) Obstetric and fetal outcomes with high risk and non-reportable low fetal fraction cell-free DNA results

Wednesday, February 14, 2024
8:30 AM – 10:00 AM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Objective:

Low fetal fraction of cell-free fetal DNA (cfDNA) is associated with a risk for adverse pregnancy outcomes and aneuploidy. This study compares outcomes for pregnancies with non-reportable low fetal fraction (NR-LFF) versus high-risk low fetal fraction (HR-LFF) results.

Study Design:

Retrospective study of singleton pregnancies with LFF cfDNA results from a SNP-based platform from 1/2020 to 1/2023 at a single institution. Patients received a HR result (1/17 risk for trisomy 18, trisomy 13 or triploidy) or a NR result based on a fetal fraction-based risk (FFBR) model that incorporates maternal age, weight and gestational age into risk assessment. Primary outcomes included aneuploidy and live birth rate. Secondary outcomes included preterm delivery (PTD), small for gestational age (SGA) and preeclampsia (preE).

Results:

There were 214 women with LFF during the study period: 61 HR-LFF and 152 NR-LFF. Women in the HR-LFF group were older, had lower BMI, and lower fetal fraction (table). Those in the NR-LFF group were more likely to repeat the screen and those in the HR-LFF group were more likely to pursue diagnostic testing, likely representing differences in counseling. Aneuploidy rates were comparable between the two groups, including no pregnancies with trisomy 18, trisomy 13 or triploidy in the HR-LFF group. Pregnancy outcomes were available for 204 (95.3%) of the cohort and were similar between groups, although there was a trend towards a lower rate of liveborn neonates in the HR-LFF group. Rates of PTD and preE were high. Most miscarriages in the cohort did not have genetic testing, which may have limited sensitivity to detect aneuploidy.

Conclusion:

Rates of aneuploidy were low in both HR-LFF and NR-LFF groups, although they may be underestimated due to incomplete genetic testing. Live birth rates trended lower in the HR-LFF group suggesting a greater risk for pregnancy loss. Overall rates of adverse pregnancy outcomes were relatively high, although there was no difference in outcomes between the HR-LFF and NR-LFF groups, suggesting these metrics are not influenced by the FFBR model.