The purpose of this study was to investigate the effects of titanium dioxide nanoparticles (\(TiO_{2}NPs\)) on pregnant mice and their embryos. \(TiO_{2}NPs\) ( 25nm, anatase) were administered orally (3500, 4500, or 5500 mg/kg) to pregnant mice daily from the \(7^{th}\) to the \(18^{th}\) gestation days. At the \(18^{th}\) gestation day, the mice were euthanized, necropsied, and pathological examination of the mice and their embryos was done. Low and medium doses of \(TiO_{2}NPs\) increased the activity of pregnant mice while high dose decreased it. Abortions occurred at a rate directly proportional to dose of \(TiO_{2}NPs\). Fetal malformations included cleft lip, cleft palate, exencephalon, exophthalmos, anencephaly, anencephalon, meningocoele, encephalomeningocoele, myelocoele, spina bifida and macromelia. Microscopically, \(TiO_{2}NPs\) induced degenerative, necrotic, and inflammatory lesions in the kidneys, liver, lungs, and brain of pregnant mice. The embryos showed delayed development of the urinary, nervous, and respiratory systems as well as degenerative and necrotic changes in the viscera. Results of this study indicated that \(TiO_{2}NPs\) in the doses used caused behavioral changes, toxic lesions, abortions, fetal malformations, and histopathological changes in both pregnant mice and their embryos.