Histologically, clinically active inflammatory bowel disease increases preterm birth risk

Histologically and clinically active inflammatory bowel disease increased the risk for preterm birth, especially for women with ulcerative colitis, researchers reported.

“Histologic remission — that is microscopic normal mucosa of the colon — is more and more recognized as a potential therapeutic target in inflammatory bowel disease, particular in ulcerative colitis, even though there are few data associating histologic remission with long-term prognostic outcomes of inflammatory bowel disease, including its influence on pregnancy outcomes,” Karl Mårild, MD, PhD, an associate professor of pediatrics at the Sahlgrenska Academy at the University of Gothenburg and a senior consultant pediatrician in the department of pediatrics at Queen Silvia Children's Hospital in Gothenburg, Sweden, told Healio.

Using the Swedish National Patient Register, Mårild and colleagues identified women diagnosed with inflammatory bowel disease (IBD) between 1990 and 2016 who had a colorectal biopsy examining histologic inflammation no more than 12 months before pregnancy. They evaluated pregnancy outcomes for these women and for women with IBD who gave birth between 2007 and 2016 who did and did not have clinically active IBD.

Specifically, the researchers determined the risks for preterm birth and small for gestational age.

In total, the researchers identified 1,223 births with histologic inflammation, 630 births without histologic inflammation, 2,110 births with clinically active IBD and 4,993 births without clinically active IBD.

Karl Mårild

“After examining prepregnancy colorectal biopsy data of women with IBD with histologic inflammation vs. histologic remission, we found a link to preterm birth,” Mårild said. “Of infants [born] to women with and without histologic inflammation, 9.6% and 6.5% were preterm, respectively. This corresponded to an almost 50% increased risk of preterm birth (adjusted RR = 1.46; 95% CI, 1.03-2.06).”

Analyses by IBD subtype revealed histologic inflammation was associated with preterm birth for women with ulcerative colitis (aRR = 1.64; 95% CI, 1.07-2.52), especially extensive colitis (aRR = 2.37; 95% CI, 1.12-5.02), compared with remission. Histologic inflammation was not associated with preterm birth for women with Crohn’s disease.

Among infants born to women with and without histologic inflammation, 9.6% and 8.9% were small for gestational age, respectively. Inflammation did not increase the risk for this outcome.

Women with clinically active IBD had a greater risk for preterm birth (aRR = 1.42; 95% CI, 1.2-1.69), but not small for gestational age compared with women without clinical activity.

Of note, women without clinical activity who had histologic inflammation did not have a greater risk for preterm birth.

“Our findings support recommendations to objectively assess IBD remission status, including histologic assessment, before pregnancy to be able to optimize management and prevent adverse outcomes of pregnancy and IBD,” Mårild said. “More research is needed to understand the importance of prepregnancy histologic activity in women without other clinical markers of disease activity.”