(626) Is cell-free fetal DNA methylation patterning different among pregnancies affected with fetal growth restriction?

To assess whether there are significant differences in maternal-fetal circulating cell-free DNA 5-methylcytosine (5mC) patterns between people carrying growth-restricted fetuses those carrying non-growth restricted fetuses.
 

Study Design:
We conducted a prospective cohort study of patients above the age of 18 with a live, singleton affected with fetal growth restriction (FGR) above 20 0/7 weeks and unaffected singletons, matched by gestational age. After consent, 4 cc of venous blood was obtained by a trained study phlebotomist. Cell-free fetal DNA was extracted from maternal serum and subjected to fetal whole genome 5mC evaluation via Ultra-Mild Bisulfite sequencing and Linear Amplification of Bisulfite Sequencing techniques, aimed at improving the yield and specificity of analyses. The primary outcome was the difference in size of maternal-fetal cfDNA fragments, while the secondary outcome was the numerical difference in upregulated and downregulated genes in cffDNA. High-throughput sequencing data was analyzed for differentially methylated gene promotors, defined as statistically significant with 20% difference in mean methylation levels between cases and controls.

Results:

We recruited 10 participants (n=5 with FGR and n=5 unaffected), of whom 9 had sufficient cffDNA for analyses. The median gestational age at diagnosis was 29 weeks. For the primary outcome, cffDNA in the FGR group exhibited more total DNA at sizes below 230 basepairs when compared to unaffected fetuses (Figure 1, sections B-C). We further identified the promoters of 688 transcripts from 502 different genes to be differentially methylated between participants with FGR and healthy controls. 273 of these promoters were significantly more methylated in participants with FGR; 415 promoters were significantly more methylated in controls (Figure 2).

Conclusion:

In this pilot study, there are differences in cffDNA 5mC patterns among fetuses affected by growth restriction compared to unaffected fetuses. Future research should evaluate its association with maternal and perinatal outcomes in the setting of FGR.