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Pregnancy & Prenatal Testing

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First Trimester: Hemoglobin

Hemoglobin is the protein in red blood cells (RBCs) that gives blood its red color. It binds to oxygen in your lungs, transports it throughout the body, and releases it to the cells and tissues. During pregnancy, a woman's hemoglobin must transport enough oxygen to meet both her and her fetus' needs. If a woman has insufficient hemoglobin, she is said to be anemic. Many pregnant women will experience some degree of anemia. Anemia can be caused by decreased RBC production, increased RBC destruction, or increased RBC (blood) loss.

Mild anemia can make you feel tired and weak, while severe anemia may cause you to lose consciousness and, in extreme cases, can cause death. Anemia in a pregnant woman can cause a fetus to receive too little oxygen to support normal development. To prevent these problems, the hemoglobin level of a woman's blood should be checked before pregnancy, if possible, at the beginning of pregnancy, and one or more times during pregnancy. The first baseline concentrations will be compared to later values to look for changes that could indicate increasing anemia.

Often, a hemoglobin test will be run as part of a Complete Blood Count (CBC). The CBC also measures the actual number of RBCs, the number and type of white blood cells (WBCs), the number of platelets, and the hematocrit.

Iron deficiency is the most common cause of anemia, but vitamin deficiency, kidney disease, inherited hemoglobin disorders, and other illnesses can also cause anemia. It is also possible to have a higher than normal hemoglobin level. This is usually caused by dehydration but may also result from a variety of diseases. Treatment for the unexpected hemoglobin level will depend upon the medical cause of the problem.

March of Dimes: Pregnancy complications – Anemia