Pregnant individuals diagnosed with inflammatory bowel disease (IBD) display higher levels of pro-inflammatory cytokines in their vaginal mucosa compared to healthy pregnant individuals, according to research published January 14, 2026, in PLOS One. The study was led by Ana Maldonado-Contreras from the University of Massachusetts Chan Medical School and her colleagues.
The researchers enrolled 48 pregnant participants in their third trimester, including 23 with IBD—18 with Crohn's disease and five with ulcerative colitis—and 25 without IBD. More than half of those with IBD were in remission at the time of recruitment. All participants provided vaginal swabs and participated in three nutrition assessments regarding their dietary intake.
The study found that although the bacterial composition of the vaginal mucosa was similar between both groups, those with IBD had higher expression of pro-inflammatory cytokines such as IL-6, IL-8, and IL-17. They also had lower levels of IFN-γ, an immune-regulating cytokine, and IL-4, an anti-inflammatory cytokine.
According to the authors: "pregnant individuals with IBD have a pro-inflammatory vaginal environment even when in remission, which may help explain their increased risk of preterm birth."
The research also observed that a diet higher in vegetables or lower in added sugars correlated with greater presence of Lactobacillus crispatus—a beneficial microbe—lower levels of pro-inflammatory IFN-γ, and increased anti-inflammatory IL-4 across all participants regardless of IBD status.
Despite its findings, the study acknowledges limitations due to its small sample size and data collection restricted to the third trimester. This limits broader conclusions about changes throughout pregnancy or definitive causation.
