Refractory ulcerative colitis (UC) that does not respond to medical therapy often requires surgery even during pregnancy. Although surgical cases of UC during pregnancy were reported previously, the standard surgical strategy for both colitis and pregnancy was unclear. Herein, fetal and maternal safety as well as the strategy for this unusual surgical procedure during pregnancy in patients with UC are considered. A 28-year-old woman was diagnosed with left-sided moderate UC at 12 weeks of pregnancy; toxic megacolon was suspected, and surgery was required. Although the baby's gestational age was 23 weeks and 3 days, a cesarean section was performed before the colectomy. In a next case, a 28-year-old woman had a 2-year history of left-sided UC. Her colitis flared up at 11 weeks of pregnancy. Colectomy was performed because her colitis was unresponsive to conservative therapy, and the pregnancy was continued, with a transvaginal delivery at 36 weeks. In patients with UC, the need for surgery should be determined promptly based on disease severity, whether or not the patient is pregnant. The need for surgery should not be affected by pregnancy. The pregnancy should be continued for as long as possible when there are no fetal and maternal complications. Both cesarean section and colectomy should be performed independently if necessary.