Late third trimester diagnosis of congenital giant hemangioma complicated by the Kasabach-Merritt phenomen: a case report and literature review.

To describe the case of a large cervical mass diagnosed in the late third trimester with development of Kasabach-Merritt phenomenon (KMP) in the immediate postnatal period, along with a literature review.. Description of case-report and literature search through Medline/Pubmed, performed from inception to December 2022 for articles relating to the pre and postnatal diagnosis of KMP. A 36-year-old multiparous woman was admitted to hospital for contractions at 40 weeks of gestation, in an otherwise uneventful pregnancy. Admission's ultrasound showed the presence of a voluminous mass of 14x15 cm of the posterior side of the neck, highly vascularized, and no signs of hemodynamic imbalance. Postnatally, blood tests showed the presence of severe anemia and thrombocytopenia requiring several transfusions of blood, plasma, platelets and clotting factors. Due to the association of congenital hemangioma and thrombocytopenia a diagnosis of KMP was made. After attempts of conservative treatment, surgical removal was needed to stop the hematological cascade with regression of symptoms. The review of the literature identified 14 articles including 9 cases of prenatally suspected KMP and 6 diagnosed in the immediate postnatal period and without signs of fetal hydrops. Adverse perinatal outcome, in terms of postnatal death/termination of pregnancy, was observed in 67% of cases (6/9) in the prenatally suspected group and 33% of cases in those with a postnatal diagnosis of KMP. Fetal hydrops was present in 83% of cases with adverse perinatal outcome. The Kasabach-Merrit syndrome is a rare condition, which can have a dangerous evolution when it develops in utero or in the immediate postnatal period carrying a risk of perinatal mortality of approximately 50%. Even if the fetus shows no signs of anemia or heart failure, the risk of developing it in the immediate postnatal period is high and should be mentioned to the couple.