(1153) Fetal Fraction in Patients with Autoimmune Diseases of the Gastrointestinal Tract

Objective: We sought to evaluate differences in fetal fraction (FF) in individuals with autoimmune diseases of the gastrointestinal (GI) tract compared to those without autoimmune disease. Additionally, we assessed whether use of immunomodulating medications (IM) at time of cell-free DNA (cfDNA) screening has any effect on FF for patients with autoimmune diseases of the GI tract

Study Design: We performed a retrospective cohort study of singleton pregnancies who had cfDNA testing 2017-2024. Patients without autoimmune disease served as controls and were matched to patients with GI autoimmune diseases (ulcerative colitis and Crohn’s) during pregnancy in a 3:1 fashion, controlling for gestational age and BMI. Exclusion criteria included those on anticoagulants, history of organ transplant, and/or high-risk cfDNA results concerning for aneuploidy. IM therapy included mesalamine, infliximab, vedolizumab, and adalimumab. We used the student t-test for normally distributed variables, chi-square and Fisher’s exact tests for categorical variables and ANOVA to compare three groups. Multivariate regression analysis was performed to evaluate the effect of immunomodulator use on fetal fraction, after adjusting for BMI and gestational age at the time of cfDNA draw.

Results: We included 300 patients in the study (75 with GI autoimmune disease and 225 without disease). Baseline demographics between the two groups were similar with respect to BMI, race, and smoking status (Table 1) with a statistically significant difference in age. Mean fetal fractions were similar in those with and without disease (Table 1). In the subset of individuals with GI autoimmune disease, use of IM medication did not result in higher fetal fraction compared to individuals with GI autoimmune disease not on IM medication, even after adjusting for gestational age and BMI (aβ .072, 95%CI -1.2, 2.3)

Conclusion: Contrary to other reports, this study found no effect of GI autoimmune disease on FF, even when adjusting for IM use. Further research is needed to assess the impact of various autoimmune diseases on FF.