From the Research
The normal ultrasonographic appearance of the uterine wall during pregnancy shows a three-layered structure consisting of the decidua, myometrium, and serosa, with the myometrium typically measuring between 7-15mm in thickness during the first trimester and gradually thinning as the uterus expands. The decidua appears as a hyperechoic (bright) inner layer lining the gestational sac, while the myometrium appears as a homogeneous, medium-echogenic layer that gradually thickens as pregnancy progresses [ 1 ]. As pregnancy advances, the uterine wall demonstrates increased vascularity, which can be visualized using color Doppler imaging [ 2 ]. Some key features to note include:
- The junction between the placenta and myometrium should appear clear and well-defined throughout pregnancy
- Any focal thinning, irregular thickening, or disruption of the normal layered appearance may indicate pathology such as placenta accreta, uterine dehiscence, or other abnormalities that require further evaluation
- The myometrial thickness can vary depending on the location and stage of pregnancy, with the lower uterine segment tend to be thinner than the upper segment [ 3 ]
- A highly positive correlation between lower uterine wall thickness and cervical length has been observed, suggesting that lower uterine wall thickness may be a useful marker for predicting preterm labor [ 4 ]. Understanding the normal sonographic appearance of the uterine wall is essential for accurately identifying potential complications during pregnancy [ 5 ].