Final answer:
Pregnancy striae, or stretch marks, are most prominent in the later stages of pregnancy, appearing as red or purple marks that fade post-childbirth. The dermis is stretched to accommodate the body changes during pregnancy, which may also include chloasma and linea nigra.
Step-by-step explanation:
Pregnancy striae, commonly known as stretch marks, become most prominent in the later stages of pregnancy when the dermis is stretched extensively to accommodate the growing uterus, breast tissue expansion, and increased fat deposits on the thighs and hips. These marks typically present as red or purple on the abdomen during pregnancy and then fade to a silvery white color in the months following childbirth.
Besides stretch marks, pregnant women often experience other integumentary system changes such as chloasma, also known as the "mask of pregnancy," which presents as blotchy brown patches on the face, and the linea nigra, a dark line of pigment extending from the umbilicus to the pubis.