Microscopic Intestinal Inflammation Linked to Increased Risk of Preterm Birth in Women with Ulcerative Colitis

Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, is a chronic condition affecting about 3 million adults in the United States. The peak age of onset is between 15 and 35 years, coinciding with peak reproductive years in women. IBD has been associated with adverse pregnancy outcomes. Data have shown that people who have active IBD at conception or who have flare-ups during pregnancy have an increased risk of miscarriages, preterm birth, low-birth-weight infants, preeclampsia and a number of other adverse outcomes.

Due to these risks, it has been recommended that conception planning include an assessment of disease activity prior to pregnancy. People planning to become pregnant may be counseled to attempt to do so after achieving endoscopic remission to reduce the risk of negative pregnancy outcomes.

Still, it is known that microscopic histological inflammation can persist even after endoscopic remission and is a risk factor for disease flare-ups. Because of this, IBD treatment goals are shifting toward histologic remission, especially in patients with ulcerative colitis. It is unclear, however, whether histological inflammation affects pregnancy outcomes similar to active disease.

A Swedish study published last November in The Lancet’s eClinicalMedicine investigated the effects of histological inflammation on pregnancy outcomes. The study, led by Karl Marild, associate professor of pediatrics at Sahlgrenska Academy, University of Gothenburg, and senior consultant pediatrician at the Pediatric Gastroenterology Unit, Queen Silvia Children's Hospital, Gothenburg, analyzed register data from Swedish women diagnosed with IBS from 1990 through 2016 and their infants. The researchers identified a total of 7,374 women who met the diagnosis criteria and narrowed their search to those with intestinal biopsies collected up to 12 months before pregnancy. The sample consisted of 1,164 women who showed histological inflammation and 611 women with histological remission. They included 1,223 children born of women with histological inflammation and 630 children born of women with histological remission.

The study’s primary outcomes were preterm birth (less than 37 gestational weeks) and small for gestational age (less than 10th percentile of birth weight for gestational age and sex) birth. Secondary outcomes included very preterm birth (less than 32 gestational weeks), low birth weight (less than 5.5 pounds), gestational diabetes, preeclampsia, and others.

Among women with histological inflammation within 12 months before pregnancy, 9.6% had preterm births versus 6.5% of women with histological remission. The increased risk of preterm birth in women with microscopic inflammation was associated with ulcerative colitis and not with Crohn’s disease. Histological inflammation was not linked to other adverse pregnancy outcomes.

The authors conclude that histological inflammation is linked with preterm birth. They suggest that IBD treatment should be aimed at controlling clinical as well as histological disease activity to reduce the risk of adverse pregnancy outcomes, such as preterm birth.