Postpartum endometrial echogenicity usually refers mainly to polyps, gestational sacs, menstrual residuals, or uterine fluid, which need to be treated as soon as they are detected. The absence of echoes in the uterine cavity is usually abnormal, and may be due to the presence of polyps in the endometrium, as the polyps themselves liquefy and may bleed to manifest the absence of echoes. Secondly, the anechoic area observed during pregnancy may also be the gestational sac, and of course, it may be due to the residual fluid from the menstrual period that is not eliminated, which manifests itself as anechoic. In addition, in some older people, due to adhesions at the cervical opening, the fluid formed in the uterine cavity will not be discharged, which can be clinically diagnosed as uterine fluid, which can also show anechogenicity in the uterine cavity.