Can birthmarks be detected during a four-dimensional ultrasound?

Under normal circumstances, a four-dimensional ultrasound examination, which is part of a comprehensive anomaly scan, can detect whether the fetus has structural abnormalities in various body parts, but it cannot identify birthmarks. The detailed explanation is as follows:

A four-dimensional ultrasound uses sound wave reflections to create images and observe fetal structure and movement. It can clearly display the fetal surface morphology, such as facial contours, limbs, spine, and the spatial relationships of other anatomical structures. However, birthmarks are caused by skin pigmentation or vascular malformations. Since ultrasound imaging primarily focuses on the internal structure and physical morphology of tissues and organs, it is difficult to distinguish superficial features such as changes in skin color or subtle vascular differences.

There are several types of birthmarks, including Mongolian spots, café-au-lait spots, and port-wine stains. These are mainly due to abnormal distribution of skin pigment cells or vascular abnormalities. Ultrasound examinations are unable to accurately detect skin pigmentation or minor irregularities in blood vessel distribution.

If a birthmark affecting appearance is found on the face after birth, laser therapy can be considered later when the child is older to remove it.