What Is a Yolk Sac in Pregnancy?

The yolk sac is a small, fluid-filled sac attached to the fetus by the umbilical cord. It is present during the early stages of pregnancy and is responsible for providing nourishment to the developing embryo. The yolk sac is visible on an ultrasound scan and is often used to confirm a pregnancy.

What are the functions of the yolk sac?

The yolk sac plays a vital role in early pregnancy, providing the developing fetus with:

* Nutrients: The yolk sac contains a liquid that is rich in nutrients, such as proteins, carbohydrates, and fats. These nutrients are absorbed by the fetus through the umbilical cord.

* Oxygen: The yolk sac also provides the fetus with oxygen. The oxygen diffuses from the mother's blood through the placenta and into the yolk sac.

* Waste products: The yolk sac helps to remove waste products from the fetus. These waste products are transported through the umbilical cord to the placenta and then expelled from the mother's body.

When does the yolk sac disappear?

The yolk sac typically disappears by the 12th week of pregnancy. This is because the fetus is now receiving all of the nutrients and oxygen it needs from the placenta.

What happens if the yolk sac doesn't disappear?

In rare cases, the yolk sac may not disappear completely. This is known as a persistent yolk sac. A persistent yolk sac is usually not harmful, but it can sometimes be associated with certain medical conditions, such as fetal chromosomal abnormalities.

If you are concerned about the size or presence of your yolk sac, talk to your doctor.