Thanatophore dysplasia is a rare lethal bone dysplasia. It is caused bya genetic mutation. There are two subtypes which are very similar in their distinct radiological characteristics and genetic mutations. Early diagnosis is imperative and based on antenatal ultrasound data.We report a case of type I thanatophore dysplasia diagnosed at 32 weeks of amenorrhea and 14 days by a routine antenatal ultrasound in an 18-year-old woman, with no known family malformation history, at the commune II reference health center. of the district of Bamako. The objective of this work is to clarify the contribution of ultrasound in the diagnosis of thanatophore dysplasia.