Oligohydramnios

Oligohydramnios is defined as decreased amniotic fluid volume (AFV) for gestational age and is associated with increased rates of neonatal morbidity. AFV is typically assessed via transabdominal ultrasound using either the amniotic fluid index (AFI) or the single deepest vertical pocket (DVP) techniques. Oligohydramnios is defined as an AFI ≤5 cm or DVP, also referred to as the maximum vertical pocket (MVP) or single deepest pocket (SDP), <2 cm. Oligohydramnios develops when the mechanisms that regulate AFV are disrupted. Most often, this is due to reduced fetal urination, uteroplacental insufficiency, or loss of amniotic fluid with membrane rupture. However, in many cases, an etiology is never identified. As oligohydramnios is a symptomatic reflection of an underlying etiology, patients should be evaluated to identify the abnormal condition resulting in low AFV. Oligohydramnios assessment comprises a targeted history and physical examination, detailed ultrasound imaging, and amniocentesis for genetic testing if fetal anomalies or history-based risk factors are identified. The management and prognosis of oligohydramnios primarily depend on the underlying pathophysiology and the gestational age at diagnosis. Increased antepartum surveillance and early delivery are typically indicated in patients with idiopathic disease.