A 33-year-old woman with Crohn disease complained of diarrhea and hematochezia from the fifth week of her third pregnancy and was hospitalized. Because her CDAI indicated 307.1 points and colonoscopy showed multiple longitudinal ulcers in the distal colon, adalimumab therapy was initiated. The CDAI had decreased to 160.0 points and the colonic ulcers improved by 22 days after beginning the administration of adalimumab. Although adalimumab therapy was continued every 2 weeks during the third trimester, fetus growth was not affected and the woman delivered a healthy child. Adalimumab should be considered as one treatment for Crohn disease during pregnancy.