Fetal Hydrops (Immune/Non-immune) Diagnostic Workflow

Step-by-step decision

Choose step by step as prompted; reaching an endpoint gives the management recommendation. You can go back a step or restart anytime.

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Full pathway

1. [Decision] Immune vs non-immune + cause-directed
   Immune vs non-immune + cause-directed? (Hydrops = ≥2 abnormal fluid collections (ascites, pleural effusion, pericardial effusion >2–3 mm, skin edema >5 mm); associated (non-diagnostic) placentomegaly (≥4 cm mid-trimester/≥6 cm third trimester), polyhydramnios, hepatosplenomegaly. First screen maternal antibodies to separate immune (alloimmune, now rare) vs NIHF (85–95%).)
   • Maternal antibody positive (Rh/other blood-group alloimmunization) → Immune → MCA-PSV + intrauterine transfusion
   • Non-immune — MCA-PSV suggests anemia (>1.5 MoM) → NIHF with anemia → intrauterine transfusion
   • Non-immune — cardiovascular/arrhythmia or monochorionic complication or chest mass → Cardiac/monochorionic/chest mass
   • Non-immune — cause unclear (initial workup negative) → Cause unclear → systematic evaluation
2. [End] Immune → MCA-PSV + intrauterine transfusion
   Immune hydrops (red-cell alloimmunization): MCA-PSV monitoring for anemia, intrauterine transfusion (IUT) treatment; maternal antibody titer + paternal antigen; timely anemia correction can reverse hydrops; Rh prophylaxis in future pregnancies.
3. [End] NIHF with anemia → intrauterine transfusion
   NIHF with anemia (MCA-PSV >1.5 MoM): causes such as parvovirus B19, alpha-thalassemia (high prevalence in the Far East), fetomaternal hemorrhage (Kleihauer-Betke), alloimmunization; cordocentesis confirmation + intrauterine transfusion; parvovirus is often self-limited, transfusion support can reverse it.
4. [End] Cardiac/monochorionic/chest mass
   NIHF cardiac/monochorionic/chest mass: fetal echocardiography (structure + rhythm) — tachyarrhythmia → transplacental antiarrhythmics; TTTS/TAPS → laser; large chest mass (CPAM/sequestration/effusion) → shunt/laser/steroids; individualized by cause.
5. [End] Cause unclear → systematic evaluation
   NIHF cause unclear: systematic evaluation — detailed anatomy + echocardiography + MCA-PSV + infection screen (parvovirus/CMV/toxoplasma/syphilis) + Kleihauer-Betke + chromosomal microarray ± karyotype; if still unclear, exome sequencing; maternal vigilance for mirror syndrome (preeclampsia-like); treat treatable causes, prognosis varies widely by cause.

Source guidelines & references

• Non-immune fetal hydrops evaluation and management (SMFM Consult #75, 2026; NEJM 2020 exome)

This pathway is our own synthesis of the decision logic in the guidelines above (not the guideline verbatim); thresholds and workflows change as guidelines update — in practice follow the latest guideline, your institution's protocol and the individual patient.

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