Pancreatic neoplasms during pregnancy are rare. We describe two cases of mucinous cystic neoplasm (MCN) associated with pregnancy. A 34-year-old woman in the 26th week of pregnancy was given a diagnosis of MCN measuring 19 cm in diameter. We decided to resect it post partum in consideration of the risk of abortion. She had a healthy infant in the 40th week of pregnancy and three months later, distal pancreatectomy was performed. Pathological analysis revealed a mucinous cystadenoma of the pancreas. The second case was a 36-year-old woman. She was given a diagnosis of MCN, measuring 16 cm in diameter, post partum and distal pancreatectomy was performed. Pathologically, the tumor was an invasive mucinous cystadenocarcinoma of the pancreas. In this report, we did an extensive literature review and discussed the management of MCN during pregnancy with special reference to the timing of the operation and the relationship between tumor growth and sex hormones.