Hydrops Fetalis

Hydrops fetalis is abnormal fluid in at least two fetal compartments: ascites, pleural effusion, pericardial effusion or generalized skin edema. It is an ultrasound pattern, not a single disease. Formal sonographic criteria define a pericardial effusion as >2–3 mm and generalized skin edema as skin thickness >5 mm. Associated findings that support the assessment but are not themselves diagnostic criteria include placental thickness ≥4 cm in the second trimester or ≥6 cm in the third trimester, and polyhydramnios with a deepest vertical pocket ≥8 cm or amniotic fluid index ≥24 cm. Use the radiology or maternal-fetal medicine interpretation rather than independently diagnosing hydrops from measurements. One fetal effusion is not yet hydrops, but it can be part of the same disease spectrum. Notify the responsible obstetric physician or nurse practitioner promptly about a newly identified effusion and arrange the ordered specialist assessment; do not wait for a second compartment to become involved. A useful handover states gestational age, every compartment affected, fetal observations, maternal symptoms and the responsible obstetric service. Distinguish fluid within fetal tissues or cavities from excess amniotic...