Mean Corpuscular Volume (MCV)

The Mean Corpuscular Volume (MCV) is a tool that helps you distinguish between microcytic and macrocytic anemia types. This can help narrow down the type of differentiation etiology. ​MCV increases or decreases, along with increases and decreases in mean corpuscular hemoglobin (MCH), are significant findings for cobalamin (vitamin B12), folate (vitamin B9), pyridoxine (vitamin B6), copper, and iron deficiencies. 

MCV Testing

​MCV measures the volume occupied by a single red blood cell or the average size of an individual red blood cell.

MCV = Total Volume of Blood/Total Number of Red Blood Cells

It is an essential component of a complete blood count (CBC) that is expressed in femtoliters. 

MCV in Pregnancy

MCV levels increase by approximately 4 fL throughout pregnancy, reaching a peak between 30 and 34 weeks. This is explained by an increase in the production and release into circulation of larger immature red blood cells.

This does not indicate a cobalamin (vitamin B12) or folate (vitamin B9) deficiency issue unless the increase is greater than 4 fL or if there are other symptoms.

If a woman experiences postpartum hemorrhage, it may impact the red blood cell indices, including MCV. With blood loss and hypoxia, immature red blood cells are produced and released, increasing the MCV value.

​Iron deficiency from blood loss can also cause a sharp decrease in MCV after immediate blood loss recovery.

High MCV in Pregnancy

An elevated MCV is a marker for macrocytic anemia.

• In pregnancy, this is defined as an MCV >100 fL and a hemoglobin <11 g/dL.
  
• This form of anemia accounts for 40% of pregnancy anemia cases.

Macrocytic anemia is divided into two distinct categories: megaloblastic and non-megaloblastic. 

Megaloblastic anemia means there are very large blood cells but not very many of them, and they are deformed. Megaloblastic anemia is caused by deficiency or impairment of the utilization of vitamin B12 or folate. This is the primary cause of macrocytic anemia and should be tested in these cases. Often, this is due to genetics. 

Non-megaloblastic anemia means the blood cells are very large, there are not many of them, and they are not deformed. It may result from liver dysfunction, alcoholism, myelodysplastic syndrome (MDS), or hypothyroidism.

Most Common Causes of High MCV in Pregnancy

• Vitamin B12 (Cobalamin) Deficiency
• Vitamin B9 (Folate) Deficiency
• Hypothyroidism
• Hypoxia
• Sleep Apnea
• Liver Inflammation
• Hemolysis
• Adrenal Hyperfunction
• Genetics

Low MCV in Pregnancy

MCV is a marker for microcytic anemia.

​You’ll see different resources saying anywhere from <80 fL to <85 fL is diagnostic for microcytic anemia in pregnancy, due to the normal increase in MCV. 

Microcytic anemia is defined as the presence of smaller-than-normal RBCs or less RBC production. Microcytic anemia is divided into three subtypes.

• Hypochromic means the RBCs have less hemoglobin, causing them to be smaller than normal.
  
• Normochromic means the RBCs have normal hemoglobin but lower RBC counts.
  
• ​Hyperchromic means the RBCs have more hemoglobin than normal. This is a very rare condition known as sideroblastic anemia. This is primarily a genetic disorder related to iron utilization in the cells. It can be secondary to nutritional deficiency, antibiotics, heavy metals, and drug use. This pattern is characterized by a low MCV and MCH and elevated RDW.

Most Common Causes of Low MCV in Pregnancy

• Iron Deficiency
• Vitamin B6 (Pyridoxine) Deficiency
• Copper Deficiency
• Vitamin C Deficiency
• Rapid and Excess Weight Gain
• Heavy Metal Exposure
• Hypochlorhydria
• Hyperthyroidism
• Thalassemia
• Certain Medications (recent antibiotics)
• Genetics

Want to Know More...

Check Out My Advanced Lab Analysis in Pregnancy Practitioner Course
​MEAC Continue Education Credits Available

start learning today!

---

Copyright © 2024 Functional Maternity, all rights reserved.
The content in this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding your medical condition. ​

---