Technical Abstract: Senna occidentalis is a toxic weed that affects a number of animal species. Very little is known about the effects of prolonged exposure to low doses of S. occidentalis on developmental toxicology. Thus, the present study evaluated the perinatal toxicity of S. occidentalis seeds in goats. Twenty one pregnant goats were fed rations containing 0% (control), 1% (So1 group), 2% (So2 group) and 4% (So4 group) mature S. occidentalis seeds from day 27 of gestation until parturition; weight gains and serum biochemistry were evaluated. Fetuses were evaluated using ultrasonographic measurements; neonates were evaluated by body morphometry, weight gains, and serum biochemistry. Fetal resorption occurred in 2 So4 dams and one dam died. Only a few minor alterations in serum biochemistry occurred in dams and kids; even so one So4 group dam had vacuolations in hepatocytes and kidneys. There was also necrosis in skeletal and cardiac muscles. For the first time lesions were observed in sciatic nerve cells. No relevant alterations in body morphometry were observed. This study suggests that 4% S. occidentalis seeds is toxic for pregnant goats, but levels of seeds less than 4% have little impact on fetal and post birth body development.