Anemia during pregnancy is far more common than many women realize, and iron deficiency accounts for 75 to 95 percent of anemia cases in pregnant people. While some degree of blood dilution is normal during pregnancy, true anemia,where hemoglobin levels drop too low,can trigger serious complications for both mother and baby. The good news: early detection and treatment can prevent many of these risks .

What Happens to Your Blood During Pregnancy?

During pregnancy, your body undergoes a dramatic shift in blood composition. Your blood volume increases significantly, but plasma (the liquid part of blood) expands more than red blood cells do. This creates what doctors call "hemodilution," or blood thinning. As a result, hemoglobin levels naturally drop during pregnancy, which is why doctors use different thresholds to define anemia in pregnant women compared to non-pregnant women .

In an iron-replete population (meaning adequate iron stores), anemia is defined as hemoglobin levels of 11 grams per deciliter or less in the first trimester, 10.5 grams per deciliter or less in the second trimester, and 11 grams per deciliter or less in the third trimester. For comparison, non-pregnant women typically have hemoglobin levels between 12 and 16 grams per deciliter .

Why Does Iron Deficiency Anemia Happen So Often in Pregnancy?

Pregnancy dramatically increases your body's iron demands, and many women simply don't have enough iron stores to meet those needs. Your growing baby, expanding blood volume, and the placenta all require substantial amounts of iron. The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant people supplement their diet with 60 milligrams of elemental iron daily .

When deficiency is detected, treatment typically involves higher doses of oral iron sulfate. Once-daily dosing is preferred because more frequent supplementation can cause constipation .

What Are the Real Consequences of Untreated Pregnancy Anemia?

The stakes of untreated anemia during pregnancy are significant. Research shows that pregnant people with anemia during the first trimester face at least a twofold higher risk of requiring blood transfusions and experiencing severe postpartum hemorrhage compared with those without anemia. Additionally, these women have approximately a 45 percent increased risk of non-transfusion-related severe maternal complications and placental abruption, a serious condition where the placenta separates from the uterine wall .

The effects extend to the baby as well. Infants born to mothers with untreated anemia are at higher risk for low birth weight and poor mental and psychomotor development. One particularly striking finding: children whose mothers had iron deficiency anemia diagnosed at 30 weeks of pregnancy or earlier showed increased risks of autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), and intellectual disability .

How to Protect Your Health During Pregnancy

• Get screened early: ACOG recommends screening all pregnant people for anemia at their first prenatal visit, ideally during the first trimester, and again at 24 to 28 weeks of gestation to catch deficiencies before they cause harm .
• Take daily iron supplementation: ACOG recommends low-dose iron supplementation for all pregnant people, except those with certain conditions like hemochromatosis, to prevent deficiency and reduce maternal anemia at term .
• Ensure adequate folate intake: Taking 0.4 milligrams of folate daily is recommended for all women contemplating pregnancy to reduce the risk of neural tube defects; women with a history of a prior fetus with neural tube defects should take 4 milligrams daily .
• Monitor for symptoms: Clinical symptoms of iron deficiency anemia include fatigue, headache, restless legs syndrome, and unusual cravings (pica), which should prompt discussion with your healthcare provider .

What Other Types of Anemia Can Occur During Pregnancy?

While iron deficiency dominates, other forms of anemia can develop during pregnancy. Folate deficiency anemia, though less common than iron deficiency, can cause elevated hemoglobin levels and may require oral folate supplementation. Vitamin B12 deficiency can also occur and requires specific workup to rule out pernicious anemia, a condition where the body cannot absorb B12 properly .

In some cases, anemia results from infections such as parvovirus B-19, cytomegalovirus (CMV), HIV, hepatitis viruses, Epstein-Barr virus (EBV), malaria, or hookworm infestation. If your medical history suggests exposure to any of these infectious agents, your healthcare provider should perform appropriate laboratory testing .

Certain genetic conditions also affect pregnancy. Women with sickle cell disease or sickle cell trait, which occurs in 1 in 12 African Americans and is also found in populations from Greece, Italy, Turkey, the Arab world, Iran, and Asia, require specialized care during pregnancy. These conditions involve abnormalities in hemoglobin structure and function that can complicate pregnancy significantly .

The Bottom Line: Why Screening Matters

Pregnancy anemia is preventable and treatable when caught early. The difference between a woman who receives screening and supplementation versus one who doesn't can mean the difference between a healthy pregnancy and serious complications for both mother and baby. If you're pregnant or planning to become pregnant, discuss anemia screening and iron supplementation with your healthcare provider at your first prenatal visit. Early detection and treatment are among the most effective ways to protect your health and your baby's development .