Highlights ► The unmetabolized compound was detected in the plasma of the rat treated with LMG. ► LMG entered the amniotic fluid through the placental barrier. ► LMG at 160mg/kg/day caused embryolethality in rats. ► LMG at 80–160mg/kg/day caused fetal developmental toxicity in rats. ► In this study, the maternal and developmental toxicity NOAEL of LMG was 10mg/kg/day.