Marginal iodine deficiency is a major health problem in pregnant women, but its impact on nerve and intelligence development in offspring has been rarely reported. Our study aimed to investigate the effects of maternal marginal iodine deficiency on nerve and cognitive development in offspring and the related mechanisms. Marginal iodine-deficient rats were given 3 μg iodine per day, while normal control rats were given 4 μg iodine daily. Western blot was used to detect the amounts of brain-derived neurotropic factor (BDNF) and early growth response protein 1 (EGR1) in the hippocampus of each group. Immunohistochemistry was used to measure c-jun and c-fos expression in the hippocampal CA1 region. Finally, the water maze method was used to measure spatial performance. Free thyroxine (FT4) levels in marginal iodine-deficient rats decreased by about 30%. Seven days after birth, EGR1 and BDNF protein levels significantly decreased in the hippocampus of marginal iodine deficiency rats compared with the normal control group. In addition, c-jun and c-fos expression in the hippocampus of 40-day-old rats was decreased in marginal iodine-deficient rats, compared with control. The spatial learning and memory ability of 40-day-old marginal iodine-deficient rats had a downward trend compared with the normal control group. FT4 significantly decreased after pregnancy in rats with marginal iodine deficiency, affecting the expression of related proteins in the brain of offspring.