(463) Fetal fraction of cfDNA from noninvasive prenatal testing as a predictor for Placenta Accreta Spectrum

Unanticipated placenta accreta spectrum (PAS) disorders pose significant risks to maternal health, and current sensitivity of prenatal ultrasound for PAS ranges from 50% to 80-90% depending on clinical expertise. We aim to examine the clinical significance of fetal fraction (FF) from noninvasive prenatal screening in PAS disorder.

Study Design:

We conducted a matched case-control study comparing FF from cfDNA testing in patients who had histologically confirmed PAS to normal controls. Cases were identified based on ICD codes and chart review for histologically confirmed PAS and cfDNA testing with reported FF. Controls were matched to cases 2:1 by gestational age at cfDNA testing, maternal BMI, maternal age, and self-reported race. Multiple gestations and pregnancies with chromosomal abnormalities were excluded.

Results:

There were 102 patients with PAS from our institution from 2013-2023. Of these, 44 patients had undergone cfDNA testing but no fetal fraction reported for 12 of them. 32 singleton pregnancies who had undergone cfDNA testing with reported FF were included in the analysis. The FF of cfDNA in PAS was significantly higher than patients with normal placentation, 9.4% vs 7.9%, p=0.038. However, in a subgroup analysis of PAS with previa (n=13) and PAS without previa (n=19), there was no significant difference in FF compared to controls. Of all patients who underwent hysterectomy at time of CD, 36% were unplanned due to uncertainty regarding PAS diagnosis from prenatal imaging.

Conclusion:

FF was higher in patients with PAS compared to matched controls. The lack of significance in the subgroup analysis may be explained by small group numbers due to the frequency of PAS and limited reporting of fetal fraction until more recent years. More research is needed to assess the potential role for FF in cases of suspected PAS.