Iron Deficiency Anemia in Pregnancy: Why a CBC Doesn't Always Tell the Whole Story
- Jun 22nd, 2026
Midwife Talks
Pregnancy places extraordinary demands on the body. One of the most common nutritional deficiencies during pregnancy is iron deficiency, which can progress to iron deficiency anemia if left untreated. Many pregnant women are told they are "anemic" based on a routine Complete Blood Count (CBC), while others are reassured that their blood counts are normal even though they are experiencing symptoms of iron deficiency. The truth is that a CBC is only one piece of the puzzle. To truly understand iron status during pregnancy, it's important to look beyond hemoglobin and hematocrit and evaluate a full iron panel whenever appropriate. Iron deficiency anemia occurs when the body does not have enough iron to produce adequate hemoglobin, the protein inside red blood cells that carries oxygen throughout the body. During pregnancy, iron needs increase significantly because your body must support: In fact, blood volume increases by approximately 40-50% during pregnancy, making iron requirements substantially higher than before pregnancy. Iron deficiency is not just about feeling tired. When iron stores become depleted, pregnant women may experience: Severe anemia during pregnancy has also been associated with: The good news is that iron deficiency can often be identified and treated before it becomes severe. Most pregnant women have a CBC performed at least once (mostly twice) during prenatal care — once with the initial labs and again at the 26-28 week mark, when the gestational diabetes screen is done. A CBC includes (but is not limited to): These numbers can suggest iron deficiency, but they do not actually measure iron stores. Think of a CBC as looking at the consequences of iron deficiency rather than the cause. By the time hemoglobin drops, iron stores may have been depleted for months. Many women experience symptoms long before anemia appears on a CBC. The way it was explained to me once is thinking in terms of a "checking account" and a "savings account." To maintain adequate numbers in your checking account you can move money from your savings account. So your checking account numbers may look great, but your savings account is being eaten away. When there's nothing left in your savings, then you'll start seeing the numbers go down in your checking account. Hemoglobin measures the oxygen-carrying protein in red blood cells. During pregnancy, anemia is generally defined as: However, a "normal" hemoglobin does not guarantee adequate iron stores. Hematocrit measures the percentage of blood made up of red blood cells. Pregnancy naturally causes blood volume expansion, which can lower hematocrit even when iron levels are adequate. This is sometimes called physiologic anemia of pregnancy. Mean Corpuscular Volume measures the average size of red blood cells. Iron deficiency often causes smaller red blood cells (low MCV), but this change may not occur until iron deficiency is more advanced. When evaluating possible iron deficiency, a full iron panel provides much more information than a CBC alone. Ferritin is the body's iron storage protein. This is often the most useful test for detecting iron deficiency before anemia develops. Low ferritin can indicate depleted iron stores even when hemoglobin remains normal. Many people with symptoms of iron deficiency have normal CBC results but low ferritin levels. Serum iron measures the amount of circulating iron in the bloodstream at the time the blood sample is drawn. Because it fluctuates throughout the day, it should not be interpreted alone. TIBC measures how much iron the body is trying to transport. When iron stores are low, TIBC often increases because the body is attempting to capture more iron. Transferrin saturation reflects how much of the body's iron transport protein is actually carrying iron. Low transferrin saturation can help confirm iron deficiency. Imagine two pregnant people: Many people assume Person B has the bigger iron problem because her hemoglobin is lower. However, Person A may actually have significantly depleted iron stores and be at greater risk of developing anemia later in pregnancy. This is why evaluating ferritin and iron studies can be so valuable. Remember the "checking" and "savings" analogy. The earlier iron deficiency is identified, the easier it is often to correct. When iron stores are addressed early, people may experience: Waiting until severe anemia develops may require more aggressive treatment, including intravenous iron infusions in some situations. If you are experiencing symptoms of iron deficiency, consider discussing the following with your provider: Every person is different, and lab results should always be interpreted in the context of symptoms, medical history, and stage of pregnancy. One of the things I value most in my midwifery practice is taking the time to truly listen to my clients. Pregnancy comes with many changes and symptoms that are often considered "normal" parts of pregnancy. While these symptoms may be common, they are not always something we should simply dismiss as "normal." Sometimes these symptoms are a result of the incredible physiologic changes occurring during pregnancy. Other times, they can be clues that the body needs additional support or that further evaluation is necessary. Rather than ordering the same tests for every client at the same time, I tailor care to each individual's history, symptoms, and clinical picture. A routine CBC is an important screening tool, but there are times when a more comprehensive evaluation — including ferritin levels, iron studies, vitamin levels, thyroid testing, or other laboratory assessments — can provide valuable information. Listening carefully to symptoms allows us to look beyond a single lab value and understand what may be contributing to how someone is feeling. My goal is to help my clients feel their best throughout pregnancy, prepare for birth, and enter the postpartum period with the strongest possible foundation for recovery. Our bodies are always communicating with us. Our job is to pay attention and respond appropriately so the body can heal, recover, and function optimally. Pregnancy is not a one-size-fits-all experience, and prenatal care shouldn't be either. By combining thoughtful listening, individualized assessment, and evidence-based care, we can often identify concerns early and create a plan that supports both maternal and fetal wellbeing. A CBC is an important screening tool, but it does not tell the whole story about iron status during pregnancy. Understanding ferritin, serum iron, TIBC, and transferrin saturation can help identify iron deficiency before it progresses to anemia. As midwives, we want to look at the complete picture — not just one number on a lab report — so that pregnant women can feel their best, support healthy pregnancies, and prepare for a strong postpartum recovery. If you have questions about your prenatal lab work or iron status during pregnancy, speak with your healthcare provider about whether additional testing may be appropriate for you.
What Is Iron Deficiency Anemia?
Why Iron Matters During Pregnancy
Why a CBC Alone Is Not Always Enough
Understanding the Numbers
Hemoglobin (Hgb)
Hematocrit (Hct)
MCV
The Iron Studies That Matter
Ferritin
Serum Iron
Total Iron Binding Capacity (TIBC)
Transferrin Saturation
A Common Scenario in Pregnancy
The Importance of Early Detection
What Should Pregnant People Ask Their Provider?
Why Listening to Symptoms Matters
The Bottom Line