Oligohydramnios is defined as an AFI of 5 cm or less, or liquor amnii is deficient in amount to the extent of less than 200 ml at term. Congenital Anomalies Associated with Oligohydramnios: Amnionic band syndrome Cardiac: Fallot tetralogy, septal defects Central nervous system: holoprosencephaly, meningocoele, encephalocoele, microcephaly Chromosomal abnormalities: triploidy, trisomy 18, Turner syndrome Cloacal dysgenesis Cystic hygroma Diaphragmatic hernia Genitourinary: renal agenesis, renal dysplasia, urethral obstruction, bladder exstrophy, Meckel-Gruber syndrome, ureteropelvic junction obstruction, prune-belly syndrome Hypothyroidism Skeletal: sirenomelia, sacral agenesis, absent radius, facial clefting TRAP (twin reverse aerial perfusion) sequence Twin-twin transfusion VACTERL (veebral, anal, cardiac, tracheo-esophageal, renal, limb) association Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 21. Disorders of Amnionic Fluid Volume. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.