<qa>  What is the most widely used type of sonography in obstetrics and gBackground Trans vaginal sonography TVS is widely used in obstetrics and gynecology. Because of the relative lack of data, there is no universal agreement on how to prevent the transmission of pathogens and the risk of infection through TVS. Whereas American guideline are more stringent, French health authorities recommend low-level disinfection of the probe between two patients with the use of probe cover, and intermediate level disinfection at least once daily and in case of visible contamination of the probe, or rupture of the probe cover. For the coupling gel, guidelines do not agree on whether or not it should be sterile. 