(460) Diagnostic value of cfDNA fetal fraction in patients with prenatally suspected placenta accreta spectrum disorder

This was a case-control study utilizing a large database of pregnancies with suspected or proven PAS delivered between 6/2012 and 7/2024 at a single academic institution. Pregnancies were excluded if FF was not reported. Other exclusion criteria were lack of suspicion for PAS on prenatal imaging, twins, fetal demise, abnormal NIPT, fetal structural anomalies, or postnatal diagnosis of a genetic/metabolic disorder. The primary outcome was mean FF in pregnancies with a final clinical diagnosis of no PAS or FIGO1-2 (less complex) versus FIGO3A-C (more complex). A generalized linear mixed model was used and FF was log-transformed to achieve normality. Results were reported as mean FF ± standard error of the mean. Adjusted means were also reported after assessing for confounders.  

Results: Of the 468 pregnancies assessed, 165 had NIPT results reporting FF. Of these, 128 met full inclusion criteria. The mean FF in the less complex group did not differ from the more complex group (9.6% ± 0.49, n=81 vs 10.7% ± 0.64, n=47; p=0.22). However, after adjusting for number of prior cesarean deliveries and maternal BMI, the mean FF in the less complex group was significantly lower than the more complex group (9.3% ± 0.48 vs 11.1% ± 0 .64, p=0.03). Other factors including maternal age, maternal medical comorbidities, gestational age at time of NIPT, and placenta previa were not found to correlate with FF or FIGO grade.

Conclusion: Higher FIGO grade PAS may be associated with a higher FF in pregnancies with prenatal suspicion for PAS. Thus, NIPT may have the potential to assist with delivery preparation and prognostication in this high-risk patient population.