['Adequate visualization of the placenta or umbilical cord during fetoscopic procedures in complicated monochorionic twin pregnancies may be difficult because of placental position and spatial constraints, as well as stained amniotic fluid. Partial amniotic carbon dioxide insufflation (PACI) has made it possible to overcome these obstacles in other fetoscopic procedures, but its value has not yet been reported in monochorionic twins.', 'Partial amniotic carbon dioxide insufflation was carried out in five expectant women with complicated monochorionic twin pregnancies between 19 + 6 to 29 + 4 weeks of gestation when adequate fetoscopic visualization of pathological placental surface vessels or the umbilical cord was impossible because of stained or too little amniotic fluid. In four cases, five fetoscopic laser ablations of pathological placental vessels in twin-to-twin transfusion syndrome (TTTS) were performed. In one discordant twin pregnancy with TTTS, PACI was carried out in order to achieve umbilical cord ligation in a recipient with omphalocele and cardiac malformation.', 'Partial amniotic carbon dioxide insufflation offered superior visualization and did not result in any acute maternal or fetal complications. After fetoscopic laser coagulation, three women delivered one fetus at 27 + 5, two fetuses at 28 + 6, and two fetuses at 35 + 4 weeks of gestation, respectively. One set of twins with TTTS was lost. Following umbilical cord ligation, the surviving twin was delivered at 37 + 2 weeks of gestation.'] Does partial amniotic carbon dioxide insufflation ( PACI ) facilitate fetoscopic interventions in complicated monochorionic twin pregnancies?