- To compare the placental pathologies and perinatal outcomes in fetal growth restriction (FGR) pregnancies with and without oligohydramnios. A retrospective cohort study, comparing placental findings in all singleton deliveries with FGR. Macroscopic placental findings were available for 1,104 singleton FGR pregnancies. A total of 397 placentas were microscopically examined; of which 89 placentas were of FGR neonates who had oligohydramnios. No significant differences in placental vascular mal-perfusion were found between pregnancies with and without oligohydramnios (69.3 vs. 74.3%; P = 0.357). Likewise, no significant differences were noted between the groups regarding diffuse villous fibrosis (10.1 vs. 4.9%; P = 0.573), and amnion cell metaplasia (65.9 vs. 64.3%; P = 0.779). Cases of FGR complicated with oligohydramnios had significantly higher rates of perinatal mortality (9.9 vs. 5.9%; P = 0.028), preterm deliveries (34.9 +/- 3.4 vs. 35.4 +/- 3.1 weeks of pregnancy; P = 0.041), and lower birth weight (1,737 +/- 542 vs. 1,845 +/- 467 g; P = 0.002) compared to FGR without oligohydramnios. Oligohydramnios is a significant risk factor for adverse perinatal outcome in FGR pregnancies; nevertheless, no significant differences in placental pathologies were noted.