by skin edema (greater than 5 mm thick). A diagnosis can also be made by identifying excess serous fluid in two potential spaces without accompanying edema. Prenatal ultrasound scanning enables early recognition of hydrops fetalis and has been enhanced with the introduction of MCA Doppler. Treatment The treatment depends on the cause and stage of the pregnancy. Severely anemic fetuses, including those with Rh disease and alpha thalassemia major, can be treated with blood transfusions while still in the womb. This treatment increases the chance that the fetus will survive until birth. Therapy for Cardiac tachyarrhythmia, supraventricular tachycardia, atrial flutter, or atrial fibrillation etiologies are maternal transplacental administration of antiarrhythmic medication(s). This type of treatment is recommended unless the fetus is close to term. Therapy for Fetal anemia caused by a parvovirus infection or fetomaternal hemorrhage is fetal blood sampling followed by intrauterine transfusion. This treatment at an advanced gestational age poses risks and should not be performed if the risks associated with delivery are considered to be less than those associated with the procedure. Fetal hydrothorax, chylothorax, or large pleural effusion associated with bronchopulmonary sequestration should be treated using a Fetal needle drainage of effusion or placement of thoracoamniotic shunt. This procedure can be performed prior to delivery if gestational age is advanced. Hydrops Fetalis resulting from fetal CPAM can be treated using either a fetal needle drainage of effusion or placement of thoracoamniotic shunt or a maternal administration of corticosteroids, betamethasone 12.5 mg IM q24 h × 2 doses or dexamethasone 6.25 mg IM q12 h × 4 doses. Therapy for hydrops fetalis derived from TTTS or TAPS requires laser ablation of placental anastomoses or selective termination. Therapy for hydrops fetalis derived from TRAPS requires percutaneous radio frequency ablation. See also Mirror syndrome References Disorders originating in the perinatal period Neonatology it:Idrope