30 Obstetrics and Gynecology Board Review •••
❍ What is the total iron requirement per day necessary in the latter half of pregnancy?
6 to 7 mg/day.
❍ Describe the utilization of iron in the body during pregnancy.
The total iron content of a healthy woman is 2 g; however, the iron stores are only about 300 mg. The fetus
and placenta take 300 mg. Normal excretion accounts for 200 mg. The increase in total volume of circulating
erythrocytes (450 mL) requires another 500 mg.
❍ Why is supplemental iron necessary in pregnancy?
The iron stores and the iron absorbed from the diet are not enough to provide for the increase in red cells and as
plasma volume increases, anemia will result unless exogenous iron is provided.
❍ Does the reticulocyte count normally change during pregnancy?
Yes. It increases after 20 weeks due to moderate erythroid hyperplasia in the bone marrow, correlated with
increased erythropoetin levels.
❍ Describe the changes in serum transferrin levels during pregnancy.
Transferrin levels increase during pregnancy as do other carrier proteins. The level may increase by as much as
100% by the end of the second trimester. This is the reason that the total iron-binding capacity (TIBC) also
increases 25% to 100%.
❍ Does iron supplementation decrease the TIBC to prepregnancy levels?
No.
❍ What is thought to be the etiology of the increase in binding proteins (like transferrin and thyroid-binding
globulin) during pregnancy?
Increased levels of circulating estrogens are thought to stimulate the liver to increase binding proteins. Women
taking oral contraceptives also have increased levels of binding proteins.
❍ During pregnancy, how much do the total erythrocyte volume (TEV), hemoglobin, hematocrit, and mean
erythrocyte volume (MCV) change both with and without iron supplementation?
Iron Supplementation No Iron Supplementation- TEV increases by 30%
- Hemoglobin decreases by 2%
- Hematocrit decreases by 3%
- MCV increases to an average of 89.7 mm^3
- TEV increases by 15%
- Hemoglobin decreases by 10%
- Hematocrit decreases by 5%
- MCV does not change from prepregnancy
mean = 84.6 mm^3
❍ Does the MCV change during pregnancy?
Without iron supplementation, the MCV does not change. With iron supplementation, the MCV increases.