Serum Chitinase 3-like-1 (CHI3L1) Has Good Correlation with Fecal Calprotectin Levels in Pregnant IBD Patients

Background: Monitoring inflammatory bowel disease (IBD) during pregnancy is challenging due tolimited use of invasive tools. While fecal calprotectin is considered reliable, its use is limited by patient adherence and availability. Blood-based markers, such as serum chitinase-3-like-1 (CHI3L1), offer a promising alternative. Aim: To evaluate whether serum CHI3L1 reflects disease activity in pregnant IBD patients, compared to standard markers and clinical questionnaires. Methods: Pregnant IBD patients were recruited from a multidisciplinary clinic. Blood samples were collected to assess inflammatory markers. Stool samples were used to measure calprotectin levels. Each visit was classified as a distinct sample for analysis. Correlations between CHI3L1 and disease activity markers were examined. Results: A total of 124 samples from 80 pregnant IBD patients were analyzed: 90 from Crohn's disease (CD) patients and 34 from ulcerative colitis (UC) patients. CHI3L1 levels showed a significant positive correlation with fecal calprotectin (r_p = 0.366, p = 0.008), ESR (r_p = 0.358, p = 0.001), CRP (r_p = 0.478, p < 0.001) and standardized clinical scoring questionnaires. Elevated CHI3L1 (>56.6 ng/mL) is a risk factor for active disease (OR 8.78, 95% CI 1.54-49.83, p = 0.014). Conclusions: Serum CHI3L1 is positively associated with established markers of inflammation and may serve as a useful non-invasive biomarker for monitoring IBD activity during pregnancy, a medical condition in which invasive procedures are not recommended. Based on CHI3L1 levels, personalized treatment for pregnant IBD patients can be tailored. However, further validation is recommended.