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Evaluation of Anemia in Pregnancy

Jul 2013 – by J. Hansen, MD

Anemia in pregnancy is defined as a value ≤11 g/dl. The most common cause of anemia in pregnancy in the Unites States is iron deficiency. Risk factors include low socio-economic status, malnutrition, multiple gestations, history of menorrhagia, and a short interval between pregnancies. Other causes of anemia include sickle cell and thalassemia, G6PD deficiency, chronic disease related to chronic liver disease, thyroid disease, uremia, chronic infections or malignancies.

All pregnant patients should have hemoglobin (Hgb) or hematocrit (Hct) and a mean corpuscular volume (MCV) drawn at the first obstetrical visit, and in the third trimester. An MCV < 80 should be evaluated with a serum ferritin level and hemoglobin electrophoresis. A low ferritin is diagnostic of iron deficiency anemia and the patients should be started on iron supplementation. The hemoglobin electrophoresis will determine if sickle cell disease (Hb AS, SC SS or SC) or other hemoglobinopathies (Hb C, D or E) are present.

A hemoglobin electrophoresis with an Hb A2 > 3.5% with a normal ferritin level is found in women with beta-thalassemia. A Hb A2 <3.5% is found in women with alpha-thalassemia, hemoglobin H disease and chronic anemia. In both cases the partner should be tested to assess carrier status, and the couple referred for genetic counseling if both are carriers of thalassemia and/or sickle cell disease.

When the Hgb is <11 and the MCV is ≥80 a reticulocyte count should be performed. A low reticulocyte count with a normal MCV is suggestive of combined iron and folate, iron and B12 deficiency, or chronic disease anemia. A low reticulocyte count with an MCV ≥100 is consistent with folate or B12 deficiency, and serum levels of folate and B12 should be evaluated. A high reticulocyte count suggests hemolysis and should prompt a peripheral smear, direct Coombs test and hemoglobin electrophoresis. The hemolysis could be due to glucose-6-phosphate dehydrogenase (G6PD) deficiency or blood loss. A diagnosis of G6PD deficiency should be considered in women of Mediterranean, Asian, Middle Eastern, Hispanic , West Indies and African descent. If blood loss is suspected based on history, a source of the loss must be identified.

Resources:

Feisullin, K. 2007. Maternal Anemia. Pg 86-90 in Maternal-Fetal Evidence Based Guidelines (First Ed.) Editor V. Berghella. Informa Healthcare

Strong, J. 2010. Hematinic Deficiencies. Pg 13-27 in The Obstetric Hematology Manual. Editor S. Pavor and B. Hunt. Cambridge University Press.

Mueller, B. 2013 Prenatal testing for the hemoglobinopathies and thalassemias. Pg. 1-12 in www.uptodate.com Editor L Wilkins-Haug, S Mahoney, V Barss. Wolters Kluwer Health.