Non‐immune hydrops fetalis: a practical guide for obstetricians

Hydrops fetalis is the accumulation of two or more fetal fluid collections, including pericardial effusion, pleural effusion(s), ascites and skin oedema. In the absence of red cell alloimmunisation, hydrops fetalis is non‐immune and affects approximately 1 in 2000 pregnancies. Non‐immune hydrops fetalis (NIHF) is associated with severe perinatal morbidity/mortality and significant maternal risks, including maternal mirror syndrome. Priorities for clinicians are determining the cause antenatally to optimise management and discuss treatment options, if available. Systematic reviews have indicated that a cause can be identified prenatally in ~60% cases. Recent evidence indicates fetal exome sequencing can provide a diagnosis in 30% of previously unexplained cases.