In general, oligohydramnios occurs in 3–5% of pregnancies and can have multiple causes, such as placental insufficiency, premature rupture of the membranes, renal or urinary tract malformations, maternal treatment with ACE inhibitors or angiotensin II type 1 receptor blockers, fetal chromosomal anomalies, or intrauterine infections [37,38]. This evidence concerns the gene ACE and placental insufficiency.