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Fetal Development
Blood Types

Can the mother's blood mix with the fetus's blood?


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January 06, 2008 12:20AM

Yes and No. During the normal course of a pregnacy, No. The mothers and babies blood does not mix or circulate together. The umbilical cord attaches to the placenta. The placenta is the "container" that keeps the baby "isolated" from the mother. The fetal blood flows through the baby, out the umbilical cord to the placenta and no further.

The placental membrane separates maternal blood from fetal blood.

Oxygen and nutrients in the maternal blood in the intervillous spaces diffuse through the walls of the villi and enter the fetal capillaries. (this unfortunately means that bad things like alcohol and drugs diffuse through the membrane, also.)

Carbon dioxide and waste products diffuse from blood in the fetal capillaries through the walls of the villi to the maternal blood in the intervillous spaces.

Just like the walls of your own digestive system, the food you eat does not come into direct contact with your blood, but the nutients get into your blood and are transferred to all parts of your body. Now for the Yes part of the answer. Certain circumstances can cause them to mix, like miscarriage, abortion, and birth. This is when diseases can be transmitted, or problems with blood RH incompatibility can occur, but that's a whole other WikiSubject.