Decidua

The decidua is the uterine lining during pregnancy

The decidua is the modified mucosal lining of the uterus (endometrium) that forms in preparation for and during pregnancy. It plays a crucial role in supporting the developing embryo and fetus and is shed during childbirth.

Structure

The decidua is divided into three regions based on their location relative to the embryo and placenta:

• Decidua basalis: This is the part of the decidua that interacts directly with the chorion and contributes to the formation of the placenta. It is located beneath the implanted embryo.

• Decidua capsularis: This portion surrounds the embryo and amniotic sac, covering the side facing the uterine cavity. As the gestational sac grows, the decidua capsularis stretches and eventually fuses with the decidua parietalis.

• Decidua parietalis: This is the remaining part of the decidua lining the rest of the uterine cavity. It eventually fuses with the decidua capsularis as the pregnancy progresses.

Function

The decidua serves several important functions during pregnancy:

• Nutritional support: It provides nutrients to the developing embryo before the placenta is fully functional.

• Immunological protection: The decidua helps protect the embryo from the maternal immune system, which might otherwise recognize it as a foreign body.

• Hormonal support: It produces hormones such as prolactin and relaxin, which are important for maintaining pregnancy.

• Structural support: The decidua helps anchor the placenta and provides a stable environment for the developing fetus.

Development

The transformation of the endometrium into the decidua is known as decidualization. This process is triggered by the hormone progesterone following ovulation and is further stimulated by the implantation of the blastocyst. Decidualization involves changes in the endometrial stroma, including increased vascularization and the accumulation of glycogen and lipids in the stromal cells.

Clinical significance

Abnormalities in the decidua can lead to complications in pregnancy, such as miscarriage, preeclampsia, and placental abruption. Proper formation and function of the decidua are essential for a successful pregnancy.

Related pages

• Endometrium
• Placenta
• Pregnancy
• Embryo
• Fetus