Endometrial changes in pregnancy

During pregnancy, the endometrium undergoes adaptive changes such as decidualization, vascular proliferation, and gland expansion to provide support for embryo implantation and placenta formation.

1. Decidualization reaction

After the fertilized egg implants, the endometrial stromal cells differentiate into decidual cells, forming decidual tissue rich in glycogen and lipids. This process is regulated by progesterone, and decidual cells secrete substances such as prolactin and insulin-like growth factors, which can inhibit maternal immune rejection and provide nutritional support for early embryos. Abnormal decidualization may lead to recurrent miscarriage or preeclampsia.

2. Vascular remodeling

Endometrial spiral arteries undergo vascular remodeling in early pregnancy, with diameter expansion and vascular smooth muscle layer replaced by trophoblasts. This change increases blood flow 10-15 times, ensuring adequate perfusion of the placenta. Vascular growth factors such as VEGF and placental growth factor are involved in regulation, and vascular remodeling disorders may cause fetal growth restriction or gestational hypertension.

3. Gland expansion

Under the action of progesterone, the endometrial glands increase in size and curvature, enhance secretory activity, and produce uterine fluid rich in glycoproteins and immune factors. These secretions constitute the "tissue nutrient fluid" that maintains embryonic development until the placenta is formed. Glandular insufficiency is associated with early pregnancy loss, while oversecretion may indicate an inflammatory response.

4. Immune regulation

The proportion of natural killer cells and regulatory T cells in the endometrium is significantly increased, forming an immune tolerance microenvironment. Decidual tissue highly expresses immune regulatory molecules such as HLA-G to prevent the fetus from being attacked by the maternal immune system. Disruption of this immune balance may lead to unexplained infertility or recurrent miscarriage.

5. Matrix remodeling

The extracellular matrix of the endometrium is restructured under the action of metalloproteinases, and the collagen fibers are loosely arranged, making the endometrium more stretchable to adapt to fetal growth. Matrix metalloproteinase inhibitors are simultaneously activated to prevent excessive degradation leading to uterine fragility. Abnormal matrix remodeling is associated with abnormal placental implantation.

It is recommended that pregnant women undergo regular ultrasound examinations to monitor endometrial thickness and blood flow, maintain a balanced diet to ensure protein and iron intake, and avoid strenuous exercise or abdominal pressure. If abnormal vaginal bleeding or abdominal pain occurs, you should seek medical treatment promptly. If necessary, intervene with progesterone preparations or low-molecular-weight heparin. Endometrial changes during pregnancy are dynamic processes and their adaptability needs to be evaluated through continuous monitoring.