[2]The decidua has a histologically-distinct appearance, displaying large polygonal decidual cells in the stroma.

Decidualization includes the process of differentiation of the spindle-shape stromal fibroblasts into the plump secretory decidual cells, which create a pericellular extracellular matrix rich in fibronectin and laminin (similar to epithelial cells).

The large granular lymphocytes (CD56 bright) are called uterine natural killer cells| (uNK cells).

After ovulation, in placental mammals, the endometrial lining becomes hypertrophic and vascular under the influence of the sex hormones, estrogen and progesterone.

As the maternal interface to the embryo the decidua participates in the exchanges of nutrition, gas, and waste with the gestation.

In invasive placental disorders like placenta accreta decidualization have been consistently found to be deficient.

Among its products are hormones commonly associated with other organs such as cortisol, CRF, GnRH, prolactin, and relaxin.