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P853 The gut microbiota of pregnant inflammatory bowel disease patients shows a low diversity, but stable profile throughout pregnancy

J. van der Giessen1, D. Binyamin2, O. Koren2, M. Peppelenbosch1, C. J. van der Woude1, G. M. Fuhler1

1Erasmus Medical Centrum, Gastroenterology and Hepatology, Rotterdam, The Netherlands, 2Bar-Ilan University, The Azrieli Faculty of Medicine, Safed, Israel


Pregnancy constitutes an altered maternal physiological state, which is not only associated with immunological changes, but also results in an alteration of the intestinal microbiota. Towards the third trimester the faecal bacterial diversity was shown to decrease, resembling an inflammation-associated dysbiosis with an overall increase in Proteobacteria and Actinobacteria. Such alterations closely resemble faecal microbiota abnormalities observed in patients with inflammatory bowel disease (IBD), where a reduced diversity, reduced butyrate-producing bacteria and increased Proteobacteria are some of the most consistently reported findings. How pregnancy affects microbial signatures in IBD patients is currently unknown. The aim of our study is therefore to characterise changes in gut microbiota that occur from first trimester to the third trimester in pregnant IBD patients.


We analysed stool samples of 46 IBD patients (32 Crohn's Disease [CD; 70%] and 14 ulcerative colitis [UC; 30%]) from our prospectively followed-up pregnancy cohort. For the control group 120 stool samples from healthy women were used (unpublished data). Bacterial 16S rRNA gene sequencing (V4 region) was performed on Illumina MiSeq and analysed using QIIME.


During pregnancy CD and UC patients showed a lower Evenness Alpha diversity than the control group (respectively q=8.18E−13 and q=4.83E−07), and IBD patients clustered separately from controls in both weighted and unweighted UniFrac principal coordinate analysis. For IBD patients, no differences in alpha or β diversity was seen between CD and UC patients. Overall, no changes in diversity were observed when comparing the different pregnancy trimesters in IBD patients. Microbial diversity was not associated with medication use or flaring of disease.


In this study, we found no significant changes in microbial diversity during pregnancy in IBD patients. As lower diversity is associated with a pro-inflammatory response, this stable microbiome could be beneficial for patients. In line with results on non-pregnant IBD patients, we found a lower diversity comparing the pregnant IBD (UC and CD) group and control group, and it is conceivable that a further decrease in diversity is therefore not observed in these patients.