Pregnant Women With Ulcerative Colitis Have a Higher Risk of Delivering Small-For-Gestational-Age Infants: The Japan Environment and Children's Study (JECS)

Aim

Ulcerative colitis primarily affects individuals of reproductive age, raising concerns regarding its impact on pregnancy, lactation, and postpartum outcomes. Although numerous international studies exist, research on the Japanese population remains limited. This study aimed to analyze data from a large-scale nationwide cohort in Japan.

Methods

Data were derived from a prospective birth cohort study conducted between 2011 and 2014 that recruited pregnant women in early pregnancy across Japan. Of the 97 075 pregnancies, 214 were complicated by ulcerative colitis. These were compared with 96 861 pregnancies without a history of ulcerative colitis in terms of background characteristics, perinatal outcomes, and neonatal findings.

Results

Pregnant women with ulcerative colitis were older and had a lower smoking rate than those without the condition. Gestational weight gain was lower in the ulcerative colitis group than in the control group. The proportion of small-for-gestational-age infants was higher in pregnancies complicated by ulcerative colitis. This risk is further elevated in patients with anemia or inflammation during early pregnancy.

Conclusions

There is limited research on the impact of ulcerative colitis on pregnancy in Japan. This study found that pregnancies complicated by ulcerative colitis were associated with a higher risk of delivering small-for-gestational-age infants. Further studies with more detailed data on disease status are needed to assess disease activity and perinatal risk better.