Reduced volume of amniotic fluid, expected for gestational age, that surrounds the fetus. It is the opposite of another pregnancy complication, namely, hydramnios. Too little fluid for an extended period of time can result in abnormal physical and behavioral development. The amount of fluid is derived from ultrasound examination, the most common measurement being the amniotic fluid index: fluid level of less than 5 cm. (or less than the 5th percentile) is taken as a diagnosis of oligohydramnios. Other indicators include the absence of a fluid pocket of 2-3 cm in depth, or fluid volume of less than 500mL at 32-36 gestation (when it is most common during pregnancy). Some 8% of pregnant women display low levels of amniotic fluid, with about 4% of them being diagnosed with oligohydramnios, with complications arising in 12% of pregnancies beyond 41 weeks. Maternal risk factors involve diabetes, hypertension and pre-eclampsia. Complications during the first half of pregnancy include, for example, miscarriage or stillbirth, and compression of fetal organs. During the second half, they include cord compression, musculoskeletal anomalies, preterm birth and intrauterine growth restriction. In severe cases, the prognosis is poor, and is usually fatal. There are a number of treatments, the most common one being maternal re-hydration with oral fluids.
See Amniotic fluid, Fetal akinesia deformation sequence (FADS), Gestational age, Hydramnios (or polyhydramnios), Intrauterine growth restriction (or retardation), Pre-eclampsia