Theoretically, if your blood count is in the upper normal range and your body iron storage is full you may give blood once during your pregnancy. However, most women start their pregnancies with a negative iron balance, due to monthly menstruation. Because of fetal iron needs, pregnant women are vulnerable to anemia with advancing gestation. Although maternal blood volume increases during pregnancy by almost 50% most of it is new plasma (watery part of blood). Also, the earlier blood is donated during the course of the pregnancy the lesser the risk to the baby. The baby's increasing needs for oxygen are met by means of increasing maternal blood volume. Therefore, it is not recommended that pregnant women be regular donors during the course of their pregnancy.