BACKGROUND AND OBJECTIVE: Considering the high sensitivity of embryo and fetus to toxic agents and increasing use of nanomaterials such as iron oxide nanoparticles in medicine, this study aimed to determine the effects of iron oxide nanoparticles and iron ions on reproductive indices of pregnant Syrian rats and neuro-behavioral development of their newborns.

METHODS: This experimental study was conducted on 49 pregnant Syrian rats, which were divided into one control and three study groups. The study groups were subcutaneously injected 100 and 1000 µg/kg of iron oxide nanoparticles and 1000 µg/kg of ferric iron ions (equivalent to the amount of iron ions in 1000 µg/kg of iron oxide nanoparticles), respectively. Injections were performed four days before mating until delivery on alternate days. Reproductive indices of pregnant rats, as well as neuro-behavioral and physical development of newborns, were evaluated with respect to sex; newborns’ development was recorded in days.

FINDINGS: Multiple neuro-behavioral reflexes and developmental indices were delayed in the study groups, especially in the group receiving 1000 µg/kg of iron oxide nanoparticles, compared to the control group. Based on the findings, cliff-drop aversion reflex (1.35±0.13 and 2.70±0.13, respectively; p<0.001),  level or vertical stick reflex(2.55±0.20 and 3.45±0.20, respectively; p<0.01), negative geotaxis (2.60±0.22 and 3.50±0.22, respectively; p<0.01), bar holding reflex (5.85±0.44 and 7.30±0.44, respectively; p<0.05), running (7.75±0.23, 8.70±0.23; p<0.01), fur development (5.90±0.18 and 6.85±0.18, respectively; p<0.001), eye opening (14.25±0.22 and 15.25±0.22, respectively; p<0.01), and testes descent (21.20±0.18 and 22.40±0.18, respectively; p<0.001) were delayed in rats receiving 1000 µg/kg of iron oxide nanoparticles, compared to the control group. However, in most cases, shorter delays were observed in groups receiving 100 µg/kg of iron oxide nanoparticles and 1000 µg/kg of iron ions, respectively.

CONCLUSION: The present study revealed that exposure to iron oxide nanoparticles in the embryonic period could lead to severe complications; also, iron oxide nanoparticles were shown to be more toxic than iron ions