[Monoamniotic twins: diagnosis and management].

Monoamniotic twin pregnancies are necessarily monochorionic and are defined by the development of two fetuses in a single amniotic cavity. This pregnancy is the result of a division of the egg between the 8th and 13th day after fertilization. The diagnosis can and should be performed during the first trimester of pregnancy. Apart from the small risk of fetal transfusion syndrome, the specificities of these pregnancies are linked to greater risk of perinatal mortality, malformations, prematurity and the persistent risk of entanglement cords until birth. Intensified obstetrical monitoring eventually requiring hospitalization followed by a premature birth around 34 SA is recommended to improve perinatal outcomes with a reduction in prenatal mortality. Reorientation toward a neonatal Level III, the proposal of a systematic course of corticosteroids and elective delivery once lung maturation is achieved are recommended. There is not enough argument to recommend specific delivery mode, although cesarean section is performed by most authors to reduce the funicular risks.