Diclofenac sodium is one of the most commonly used non-steroidal anti-inflammatory drugs. It may cause alteration in the nervous system during neuronal development. However, there is no investigation concerning its role in the cervical spinal cord. Pregnant rats were divided into two groups, namely drug-treated and control (saline-injected) groups. To obtain the offspring of the drug-treated group, a dose of 1 mg/kg daily diclofenac sodium (Voltaren, 75 mg/3 ml ampoule, Novartis) was injected into the pregnant rats beginning from the 5th day after mating to the 20th day of the pregnancy. To obtain the control group of offspring, serum physiological at a 1 ml/kg daily dose was injected into the pregnant control rats during the same period. Male offspring were obtained after delivery and each group was divided into two subgroups: 4-week-old and 20-week-old. The total neuron number in diclofenac sodium-treated rats was significantly lower than in the control group animals. The total volume of the cervical spinal cord segments (C1-C4) was also estimated. There was a significant difference between the volumes of the two groups, especially in the 20-week-old subgroup. This may suggest that development of neurons and volume of cervical spinal cord are affected in prenatal animals after administration of diclofenac sodium. (C) 2011 Elsevier Inc. All rights reserved.