This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Amniotic Fluid Dynamics, Subject name: Gynaecology & Obstetrics
Oligohydramnios is seen in: 
Select and explain. 
A. Renal agenesis, B. Cholangioma of placenta, C. Spina bifida, D. Esophageal atresia
A: Renal agenesis
Answer: A: Renal agenesis 
Explanation: Oligohydramnios can be caused by - Renal anomalies Uteroplacental insufficiency: IUGR ACE inhibitors Premature rupture of membranes Amniocentesis (leak) Pre-ecclampsia Amnion nodosum NSAIDs Post term pregnancy over estimated gestational age The sonographic diagnosis of oligohydramnios is usually based on an AFI < 5 cm or a single deepest pocket of amnionic fluid of < 2 cm