Deltamethrin (DEL) is a synthetic pyrethroid insecticide used extensively to control insect pests of field crops and in public health programs. Women, during gestation and/or lactation periods may get exposed to low doses of DEL from different sources, and this may affect the mother’s health and her baby. Here, we test the effect of two different doses of DEL on some hepato-renal functions, and oxidative stress biomarkers, as well as the histopathological changes in selected organs. The possible protective role of selenium was also investigated. A total of twenty-four pregnant rats at gestational day 0 (GD 0) that are not exposed to any pesticides until parturition (PND) 0 were segregated equally into six groups. After parturition (PND 0), two groups were assigned for DEL-1/10 LD50 and 1/100 LD50, two other groups for DEL + selenium (Se), one group was administered Se and the sixth group served as negative control (water). The doses of DEL and Se were given to the dams orally by gavage for 21 days (lactation period). Compared with the control, animals treated with DEL recorded high elevation in alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), creatinine and malondialdehyde (MDA) levels, as well as severe decline in the levels of butyryl cholinesterase (BuChE), urea, superoxide dismutase (SOD) and in total antioxidant capacity (TAC). Also, DEL produced noticeable histopathological changes in liver, kidney and ovary. Co-administration of Se in conjunction with DEL improved the enzyme levels of liver and kidney as well as the antioxidant biomarkers. It was concluded that low doses of DEL may induce oxidative stress to the rat dams and their offspring, but selenium may alleviate such hazards to a great extent.