32-week fetus: reduced fetal movements/hypotonia + AFI 30 cm + no contractures
| Finding / Condition | Fetal Movements | Contractures | AFI | Stomach | Other Useful USG Clues | Relevance in This Case |
|---|---|---|---|---|---|---|
| SMA, severe phenotype | Markedly reduced/absent | May be absent early; may develop later | ↑, especially with bulbar weakness | Often small/poorly filling if swallowing impaired | Reduced limb movement, weak breathing movements, normal CNS | Important DD |
| SMA, intermediate/milder | Reduced but present | Usually absent | Usually normal; may be ↑ | Usually normal filling | No major structural abnormality | Possible, but AFI 30 less typical |
| Congenital myopathy | Reduced | Variable, often absent | May be ↑ | Usually normal or reduced swallowing | Weak movements, sometimes abnormal facial/tongue movements | Important DD |
| Congenital muscular dystrophy | Reduced | May be absent | May be ↑ | Variable | Muscle weakness ± brain/eye abnormalities depending on gene | DD |
| Fetal akinesia deformation sequence | Severely reduced/absent | Usually prominent | Often ↑ | May be small | Arthrogryposis, abnormal limb position, facial abnormalities, small thorax | Less likely because no contractures |
| GLDN-related lethal congenital contracture syndrome | Severe reduction | Usually present | ↑ | Swallowing impairment common | Severe akinesia, contractures, abnormal thoracic/respiratory movements | Less likely without contractures |
| Myotonic dystrophy | Reduced | May occur | May be ↑ | Poor swallowing may occur | Polyhydramnios, reduced movements; maternal myotonia may provide clue | DD |
| Neuromuscular junction disorder | Reduced | Usually absent | May be ↑ | Swallowing may be impaired | Reduced facial, swallowing and respiratory movements | DD |
| Esophageal atresia | Usually normal | Absent | ↑ | Small/absent or intermittently visible | Absent/poorly visualized stomach, pouch sign | Consider if stomach repeatedly small |
| Duodenal obstruction | Usually normal | Absent | ↑ | Persistently enlarged stomach ± double-bubble | Double-bubble, proximal duodenal dilatation | Consider if stomach is persistently large |
| Pyloric/antral obstruction | Usually normal | Absent | May be ↑ | Persistently distended stomach | Enlarged stomach without typical double-bubble | Consider with persistently large stomach |
| CNS disorder | Reduced | Variable | May be ↑ | Variable | Brain malformation, abnormal tone/posture | Must exclude |
| Chromosomal/genetic syndrome | Variable | Variable | Variable | Variable | Multiple anomalies, FGR/overgrowth, abnormal CNS/cardiac findings | DD depending on phenotype |
| Isolated polyhydramnios | Normal | Absent | ↑ | Normal cyclic filling/emptying | No structural abnormality | Possible if movements are actually normal |
Important interpretation of the stomach
| Stomach Finding | Interpretation |
|---|---|
| Full at one scan | Usually physiological |
| Fills and empties during observation | Supports normal swallowing and gastric emptying |
| Persistently small/absent + polyhydramnios | Suggests impaired swallowing or upper GI obstruction |
| Persistently large/distended + polyhydramnios | Suggests gastric outlet/duodenal obstruction |
| Normal stomach + polyhydramnios + objectively reduced movements | Neuromuscular disease remains possible, but significant bulbar dysfunction is less likely |
D/D
1. SMA / congenital myopathy
2. Neuromuscular junction disorder
3. Myotonic dystrophy
4. CNS disorder
5. GI obstruction if the stomach is persistently abnormal
6. Fetal akinesia sequence, although absence of contractures makes it less typical