Anemia during pregnancy increases the risk of complications for both you and your baby, ranging from excessive bleeding after delivery to preterm birth and low birth weight. About 35.5% of pregnant women worldwide are affected, making it one of the most common pregnancy conditions. Most cases are caused by iron deficiency, though low levels of folate or vitamin B12 can also be responsible.
Why Pregnancy Makes Anemia More Likely
Your blood volume increases by roughly 50% during pregnancy to support the growing placenta and baby. Your body needs significantly more iron to produce all that extra blood, and if your stores can’t keep up, your hemoglobin drops. Hemoglobin is the protein in red blood cells that carries oxygen, so when levels fall too low, your tissues and your baby’s tissues get less oxygen than they need.
The thresholds for anemia shift slightly by trimester. In the first and third trimesters, a hemoglobin level below 11 g/dL is considered anemic. In the second trimester, the cutoff drops slightly to 10.5 g/dL because blood volume peaks and naturally dilutes your red blood cells. These numbers are lower than the standard cutoff for non-pregnant women (12 g/dL), which sometimes causes confusion.
Symptoms You Might Notice
Mild anemia often produces no obvious symptoms, which is why routine blood work during prenatal visits matters. As it progresses, you may feel persistent fatigue that rest doesn’t fix, notice a fast or pounding heartbeat, feel short of breath during light activity, or look unusually pale. These symptoms overlap with normal pregnancy tiredness, so many women dismiss them. If your energy level feels disproportionately low, it’s worth mentioning at your next appointment rather than assuming it’s just pregnancy.
Risks to You During and After Delivery
The most well-documented maternal risk is postpartum hemorrhage, or excessive bleeding after birth. A large cohort analysis published in The Lancet Global Health found that the risk of significant postpartum bleeding was 6.2% in women with moderate anemia and jumped to 11.2% in women with severe anemia. For every 10-point drop in hemoglobin before delivery, the odds of postpartum hemorrhage increased by about 29%.
Severe anemia carries even graver consequences. Women with severe anemia had seven times higher odds of death or a life-threatening near-miss event compared to those with moderate anemia. The body simply has less reserve to cope with the blood loss that naturally occurs during delivery. This is why treating anemia before your due date, rather than after, is so important.
How Anemia Affects Your Baby
Babies born to anemic mothers face a substantially higher chance of being born too early or too small. A large meta-analysis found that women with normal hemoglobin levels were roughly four to five times less likely to deliver a low-birth-weight baby or have a preterm birth compared to anemic women. Low birth weight and prematurity are linked to longer hospital stays, feeding difficulties, and health challenges in infancy.
The type of nutrient deficiency matters, too. When anemia is caused by low folate or low vitamin B12, the risks extend to neural tube defects, which are serious birth defects affecting the brain and spinal cord. These include spina bifida, where the spine doesn’t close properly, and anencephaly, where parts of the brain and skull don’t form. Folate deficiency also raises the risk of placental abruption, a dangerous condition where the placenta separates from the uterine wall before delivery.
Effects on Your Child’s Development
The impact doesn’t necessarily end at birth. A prospective cohort study tracking mothers and infants found that children born to women who were iron-deficient in early pregnancy (around 15 to 20 weeks) scored lower on both language and motor development assessments at age two. The language scores were about 6 to 7 points lower, and motor scores were about 4 to 6 points lower, compared to children of iron-sufficient mothers. Notably, these effects were seen even in mothers who were iron-deficient but hadn’t yet become technically anemic, suggesting that waiting until hemoglobin drops into the anemic range may already be too late for optimal fetal brain development.
Treatment and What to Expect
Oral iron supplements are the first-line treatment. The WHO recommends 30 to 60 mg of elemental iron daily for pregnant women, typically paired with 400 micrograms of folic acid. If you’re already anemic rather than just supplementing preventively, your provider will likely recommend a higher dose. Iron is best absorbed on an empty stomach or with vitamin C, and it commonly causes constipation or nausea, which leads many women to take it inconsistently.
If you’re taking your supplements regularly, you should see your hemoglobin begin to rise within about two weeks. Your provider will typically recheck your levels two to four weeks after starting treatment to confirm it’s working. Rebuilding your iron stores fully takes longer, often several months, which is why early detection gives you the most time to recover before delivery.
When oral iron isn’t enough, whether because of side effects, absorption problems (common in women with inflammatory bowel disease), or because delivery is less than three weeks away, intravenous iron becomes an option. IV iron isn’t given during the first trimester due to the risk of allergic reactions, but it’s generally considered safe after 14 weeks and works faster than oral supplements. It’s typically reserved for women with hemoglobin below 8 g/dL, those who can’t tolerate pills, or those at high risk for major blood loss during delivery.
Iron Deficiency vs. Other Types
Iron deficiency causes the vast majority of pregnancy anemia, but it’s not the only kind. Folate deficiency anemia produces abnormally large, poorly functioning red blood cells and is particularly dangerous in early pregnancy when the neural tube is forming (typically weeks 3 through 4). This is why folic acid supplementation is recommended starting before conception if possible.
Vitamin B12 deficiency anemia works similarly and also raises the risk of neural tube defects. It’s more common in women who follow vegan or strict vegetarian diets, since B12 is found almost exclusively in animal products. Both folate and B12 deficiencies can exist alongside iron deficiency, which is why prenatal bloodwork usually checks for all three.
What You Can Do
Preventing anemia is far easier than treating it mid-pregnancy. Taking a prenatal vitamin with iron and folic acid before or as soon as you learn you’re pregnant builds your reserves early. Iron-rich foods like red meat, lentils, spinach, and fortified cereals help, though plant-based iron is absorbed less efficiently than iron from animal sources. Pairing plant-based iron with something acidic, like tomatoes or citrus, improves absorption.
If you’ve been diagnosed with anemia, consistency with your supplements matters more than anything else. The side effects are real, but spacing doses, taking them with a small amount of food if needed, or switching formulations can help. Your hemoglobin levels at the time of delivery are what determine your risk profile, so the weeks you spend building those levels back up are directly protective for both you and your baby.