We describe two patients who developed progressive ascending paralysis associated with Guillain-Barré syndrome (GBS) during late pregnancy. A 25-year-old woman in the 30th week of gestation (GW) developed diarrhea followed by GBS and weakness of the bilateral facial muscles. Serum IgM antibody titers against cytomegalovirus (CMV) were high. Respiratory insufficiency developed at GW 31 requiring cesarean section and artificial ventilation. The facial palsy and limb paralysis persisted thereafter. Serum anti-GM2 IgM and anti-GalNAc-GD1a IgM antibodies were positive so immunoadsorption therapy (IAT) was applied. These antibody titers decreased with clinical improvement after IAT. The baby was healthy and did not have CMV. The other patient was a 24-year-old woman at GW 28 in whom GBS developed after a common cold. Right facial muscles were also weak and serum anti-GM2 IgM antibody was positive. Cesarean section was performed because of uterine bleeding. The clinical findings improved thereafter and the baby was healthy. The findings show that the course of GBS that develops after CMV infection can be severe and accompanied by respiratory insufficiency.