Objective It has been reported that nitric oxide (NO) might play an important role in the development of intrauterine growth retardation (IUGR). This paper aims at investigating the effect of L arginine (L Arg) on NO levels of maternal and neonatal umbilical blood in IUGR. Methods Sixty six pregnant women with IUGR were recruited. Thirty six cases were given routine therapy (Routine therapy group), and the other 30 cases were given L Arg combined with routine therapy (L Arg group). Another 30 cases with normal pregnancy were used as Normal control group. The NO levels of maternal and neonatal umbilical blood were monitored before and after treatment. Results After the treatment, the maternal serum NO level in the L Arg group was significantly higher than that of the Routine therapy group ( 58.42 ± 23.12 μmol/L vs 43.49 ± 20.27 μmol/L) (P< 0.01 ). The umbilical blood NO level in the L Arg group was alao significantly higher than that of the Routine therapy group ( 25.23 ± 12.05 μmol/L vs 16.95 ± 11.19 μmol/L) (P< 0.01 ). Conclusion L Arg can increase serum NO levels of both maternal and umbilical blood in IUGR.