ABSTRACT
Oligohydramnios occurs in 0.5-1% of pregnancies. The diagnosis is usually made subjectively. It is defined as an amniotic fluid index (AFI) of less than 5 cm or a deepest single pocket measurement of 1 cm or less. Oligo-anhydramnios is caused because there is reduced production of fetal urine (e.g. placental insufficiency, renal agenesis), or because the fetus cannot urinate due to an obstruction (e.g. posterior urethral valves), or because the fluid that is produced drains away due to rupture of the membranes (ROM). Anhydramnios means that no amniotic fluid is seen. With anhydramnios there is marked fetal deformation due to fetal compression, including a flattened face, hypertelorism, low-set ears, and micrognathia (Potter syndrome).
