Oligohydramnios is associated with
Etiology of oligohydramnios: 

Intrauterine growth restriction
Post-term pregnancy 
Premature rupture of membrane 
Drugs like ACE inhibitors and prostaglandin inhibitors 
Renal anomalies 
Renal Agenesis 
Infantile polycystic disease 
Upper urinary tract obstructions 
Lower urinary tract obstructions
Renal agenesis
Neural tube defects
Postmature birth
Premature birth