In utero PTU treatment caused a slight decrease in crown-rump lengths in rat fetuses. Fetal tissues from rat dams treated with vehicle, PTU, or MMI from GD 6–19 were analyzed at GD 20. A) No effects on placenta weights were observed with PTU or MMI treatment. B) The higher dose of PTU (100 mg/kg) resulted in lower fetal weights. C) Both PTU (50 and 100 mg/kg) and the higher MMI (20 mg/kg) dose significantly reduced the mean crown-rump lengths of fetuses compared to vehicle controls. Rat dams were treated with vehicle (n = 9), 50 mg/kg PTU (n = 11), 100 mg/kg PTU (n = 8), 10 mg/kg MMI (n = 10), and 20 mg/kg MMI (n = 10). *p ≤ 0.005.