An example of the placental-myometrial interface in a second trimester fetus. This fetal evaluation was for an intrathoracic finding on ultrasound. At no point was the placenta considered abnormal and the delivery was normal.
The normal gravid myometrium has three layers:
- T2 hypointense outer layer
- T2 hyperintense middle layer
- T2 hypointense inner layer
In some images, the interface between the placenta and the inner myometrium may be blurred, but this is not uncommon and usually artifactual. Make sure you can see placental-myometrial abnormality in two planes before suggesting placental invasion. In this case, there is a small amount of blurring of the interface on the sagittal image, but it does not hold up on the axial image.
The placenta normally has homogeneous signal intensity when <24 weeks.