Introduction: Prescribing routine Iron supplementation during pregnancy has been done regardless of their need for many years. Considering the possibility of adverse pregnancy outcomes with unnecessary consumption of iron supplementation in pregnant women, this study was performed with aim to assess the effect of iron supplementation in pregnant women with high hemoglobin on neonatal jaundice. Methods: This double-blind controlled randomized clinical trial was performed on 140 nonsmoker healthy pregnant women with gestational age of 14-18 weeks and singleton pregnancy with Hb >13.2 g/dL and ferritin >15 µg/l in Ardabil during 2016-17. Mothers were randomly assigned to 50 mg ferrous sulfate and placebo groups from 20th weeks of pregnancy. Also, 24 hour after delivery, the neonates were assessed in terms of bilirubin level (by photometric method using BT3500 device) and jaundice. Data were analyzed by SPSS software (version 16) and independent t-test, Chi-square, and exact fisher test. P<0.05 was considered statistically significant. Results: There was significant difference between two groups in Hb (P=0.03) and ferritin (P=0.04) levels after the intervention, but no significant difference was found between two groups in the incidence of anemia (Hb<11 g/dl) (P<0.001). In addition, the incidence of neonatal jaundice was more in interventional group than placebo (P=0.005). The incidence of neonatal jaundice was associated with first-trimester ferritin (P=0.01). Conclusion: Iron supplementation in pregnant women with Hb >13.2 g/dl is associated with increased risk of neonatal jaundice; therefore, routine prescribing of iron supplementation should be done with caution in pregnancy.