This site is targeted at medical and radiology professionals, contains user contributed content, and material that may be confusing to a lay audience. Use of this site implies acceptance of our Terms of Use.

Oligohydramnios

Dr Yuranga Weerakkody and Dr Mohamed Refaey et al.

Oligohydramnios refers to a situation where the amniotic fluid volume is less than expected for gestational age. Often these fetuses have < 500 mls of amniotic fluid.

Epidemiology

The estimated prevalence can be up to ~ 6% of pregnancies ⁴.

Pathology

Causes

The causes of oligohydramnios are protean and one way to simplify it is by using the following mnemonic >> DRIPPC

d -
- demise
- drugs: e.g protaglandin inhibitors (Indomethacin)
r - renal abnormalities (from decreased urine output)
I - IUGR (intra-uterine growth restriction) : 80%: may occur from decreased renal perfusion due to sparing effect
p - premature rupture of membranes
- premature rupture of membranes (PROM)
- pre term premature rupture of membranes (PPROM)
p - post dates
c - chromosomal anomalies (especially if other anomalies are found)

Associations

Potter sequence
underlying fetal hypoxia and fetal cardiovascular compromise : from preferential flow to the fetal brain at the expense of renal shut down
twin pregnancy related complications :
- twin to twin transfusion syndrome : in pump twin
maternal dehydration

Radiographic assessment

Antenatal ultrasound

Several sonographic criteria can be used which include

four quadrant amniotic fluid index (AFI) - < 5
two diameter pocket method - < 1 x 1 cm or < 15 cm²
maximum vertical pocket depth - < 2 cm

Complications

first trimester oligohydramnios can result in failure of pregnancy in up to 95% from complications such as
- pulmonary hypoplasia - implies a very poor prognosis
- fetal limb contractures

Treatment and prognosis

Development of oligohydramnios early is pregnancy is generally a poor prognostic marker. An amnio-infusion can be carried in severe cases in the appropriate situation.