Capillary malformation arteriovenous malformation syndrome (CV-AVM) is marked by the appearance of vascular lesions on the skin, frequently found on the face and limbs. The main genetic defect in this syndrome is a mutation in the RASA-1 gene transmitted in an autosomal dominant manner. Besides, this syndrome is characterized by a wide intra- and interfamilial variability in clinical manifestations. In fact, little is known about prenatally diagnosed cases of CV-AVM. Here, we report the case of a 25 year-old woman admitted during her third pregnancy for management of unexplained polyhydramnios. Prenatal genetic analysis (Mendeliom sequencing from amniotic fluid), performed due to two previous unexplained fetal losses, showed a mutation in a heterozygous state in RASA-1 gene c.2367 C>T (p.Arg789*). Hence, an antenatal diagnosis of CV AVM was then made. An emergency cesarean section was performed at 31 5/7 weeks due to complications of the second amnioreduction. At birth, the neonate presented five erythematous lesions with diameters of 1-3 cm, similarly to those found on the father. No signs of arteriovenous malformations was detected on MRI of the brain and spine. No other anomaly has been found. Despite its autosomal mode of transmission, CV-AVM is still underrecognized due to its variable clinical presentation. Our report underlines that CM-AVM should be considered at the first clinical examination of a neonate revealing atypical capillary malformations especially in the context of unexplained polyhydramnios, previous fetal losses, or family history of clinical presentation of CM. When genetic diagnose is made a follow-up should be organized during the period of early childhood.