On ultrasound evaluation of a fetus at 20 weeks gestation, the amniotic fluid index (AFI) is 5 cm. This indicates:

• A Normal amniotic fluid volume
• B Polyhydramnios — associated with fetal anomalies and maternal diabetes
• C Borderline low — requires repeat scan but no immediate action
• D Oligohydramnios — associated with renal agenesis, IUGR, and post-dates pregnancy ✓

Explanation

AFI (sum of deepest vertical pocket in each of 4 uterine quadrants) of ≤5 cm indicates oligohydramnios at any gestational age. Oligohydramnios is associated with renal agenesis (Potter sequence), posterior urethral valves, severe IUGR (reduced fetal urine output), prolonged rupture of membranes, and post-dates pregnancy. Polyhydramnios is AFI >25 cm (or single deepest pocket >8 cm), associated with fetal anomalies (esophageal atresia, anencephaly, neuromuscular disorders causing swallowing difficulty) and maternal diabetes. Normal AFI is 8-25 cm; borderline is 5-8 cm.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.