What is the underlying cause of pregnancy-induced megaloblastic anemia?

The underlying cause of pregnancy-induced megaloblastic anemia is related to blood and bone marrow abnormalities, specifically the need for increased folate during pregnancy. Megaloblastic anemia is typically characterized by the presence of larger than normal red blood cells due to impaired DNA synthesis. This impairment is often due to a deficiency in vitamin B12 or folate, which are crucial for the proper formation of red blood cells.

During pregnancy, the demand for folate increases significantly to support fetal development and placental growth. If the dietary intake does not meet this increased requirement, it can result in insufficient folate levels, leading to megaloblastic anemia. The bone marrow responds to the lack of folate by producing larger, immature red blood cells that are not effective in oxygen transport.

In contrast, impaired iron absorption, hemolytic reactions, and dehydration generally do not lead directly to megaloblastic anemia. Impaired iron absorption typically results in microcytic anemia, hemolytic reactions are associated with destruction of red blood cells rather than their production, and dehydration primarily impacts blood volume and concentration but does not cause the specific changes seen in megaloblastic anemia. Therefore, blood and bone marrow abnormalities related to folate deficiency are central to understanding this