Polyhydramnios or oligohydramnios on routine US
Recommended: Detailed Obstetric Ultrasound + AFI / SDP measurement is the preferred imaging study for polyhydramnios or oligohydramnios on routine us. AFI > 24 = polyhydramnios; AFI < 5 = oligohydramnios.
Recommended study
Detailed Obstetric Ultrasound + AFI / SDP measurement
AFI > 24 = polyhydramnios; AFI < 5 = oligohydramnios. Search for fetal or maternal cause.
If the default doesn't apply
Polyhydramnios + structural anomaly suspected
MRI
Fetal MRI
No contrast
Watch-outs
Polyhydramnios + diabetes / TEF
Maternal diabetes (most common); fetal swallowing problems (TEF, neuro disorders); twin-twin transfusion.
Oligohydramnios + IUGR
Indicates placental insufficiency; consider doppler studies (umbilical, MCA, ductus venosus).
Pearls
- Idiopathic in 60% of polyhydramnios.
- Anhydramnios is severe — usually renal cause (bilateral agenesis / PUV) or PROM.
- Amnioreduction for symptomatic polyhydramnios.