This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hydramnios and Oligo Hydramnios, Subject name: Gynaecology & Obstetrics
Polyhydramnios is seen in all except: 
Select and explain. 
A. Diabetes me1litus, B. Anencephaly, C. Trachea- esophageal fistula, D. Renal agenesis
D: Renal agenesis
Answer: D: Renal agenesis 
Explanation: Ans: D (Renal agenesis) Ref: Ian Donald: Practical Obstetric Problems 6th ed. Pg 366, D.C.Dutta's Textbook of Obstetrics, 7th ed. pg. 211,215.Explanation:The main source for amniotic fluid is fetal urine.So, when there are no kidneys, there is no urine.So, it results in oligohydramnios.Hence. D (Renal agenesis) is the answer.Causes for HydramniosFetal malformationsCNS defects -AnencephalySpina bifidaHydrocephalus Cardiac defectsVSDASDPulmonary stenosisCraniofacialCleft lipCleft palateChoanal atresiaThoraxDiaphragmatic herniaGastrointestinalOesophageal atresiaTracheo-esophageal fistulaMaternal causesDiabetesMultiple pregnancy.