Iron might not be the first nutrient that comes to mind when you think about pregnancy, but it’s one of the most important for both your health and your baby’s development. From delivering oxygen to your growing baby to supporting their developing brain, iron plays an essential role in some of the most fundamental processes happening throughout pregnancy.

And here’s what makes iron particularly interesting: your body doesn’t need the same amount of it throughout all nine months. As pregnancy progresses, your blood volume expands, your baby grows, and the demand for iron increases dramatically. The iron stores you enter pregnancy with may look very different from what you have available by your third trimester.

Despite this, standard prenatal care doesn’t always provide a complete picture of iron status. Most pregnant women have a complete blood count (CBC) performed twice during pregnancy to screen for anemia, but ferritin, the marker that helps us understand how much iron the body has stored, isn’t routinely included unless there’s a specific reason to investigate further.

At Parenthood Wellness, we believe there’s value in understanding iron status before deficiency progresses to anemia. That’s why we favor checking ferritin alongside a CBC in each trimester, using that information to understand changing needs and guide individualized recommendations in collaboration with your prenatal provider.

First, why is iron so important?

To understand why iron requirements increase so dramatically during pregnancy, it helps to understand what iron actually does in the body.

One of iron’s most important jobs is helping transport oxygen. Iron is an essential component of hemoglobin, the protein inside red blood cells that binds oxygen in the lungs and carries it throughout the body. Every tissue, organ, and cell depends on a steady supply of oxygen to produce energy and function properly. Without enough iron, the body eventually struggles to produce sufficient healthy red blood cells, reducing its capacity to deliver oxygen where it’s needed.

During pregnancy, this oxygen-delivery system becomes even more important. Your body is supporting not only your own organs and tissues, but also the placenta and a rapidly developing baby. Oxygen and nutrients are transferred through the placenta to support fetal growth, making healthy maternal circulation and red blood cell production essential.

But iron does much more than help make red blood cells. It’s also involved in mitochondrial energy production, DNA synthesis, immune function, and the production of certain neurotransmitters. These roles are particularly relevant during pregnancy because your baby’s brain and nervous system are developing at an extraordinary pace.

Iron is involved in processes such as myelination, which helps nerve cells communicate efficiently, and the development of neurotransmitter systems involved in learning, attention, and behavior. This is one reason researchers are so interested in the relationship between iron availability during pregnancy and neurodevelopment later in childhood.

In other words, iron isn’t simply a nutrient we need to avoid anemia. It’s an essential building block for healthy growth and development.

Your iron needs change dramatically throughout pregnancy

One of the most fascinating physiological changes during pregnancy is the expansion of maternal blood volume. By late pregnancy, total blood volume has typically increased by approximately 40–50%, although the degree of expansion varies between individuals. Your body increases its production of red blood cells to help accommodate this change, and making those additional cells requires substantial amounts of iron.

At the same time, the placenta is developing, your baby is growing, and iron is being transferred across the placenta to support fetal tissues and build their own iron reserves. Together, these processes create a progressively increasing demand on maternal iron availability.

For nonpregnant women ages 19–50, the recommended dietary allowance for iron is 18 mg per day. During pregnancy, that recommendation increases to 27 mg per day, reflecting the much greater total iron requirement. However, that 27 mg recommendation is designed to cover pregnancy as a whole. The actual physiological demand for absorbed iron changes considerably from one trimester to the next.

These figures represent iron that must actually be absorbed and used by the body, not the amount someone should take in a supplement. Dietary iron absorption varies depending on iron status, the type of iron consumed, and other dietary and physiological factors. In fact, the body normally adapts to pregnancy by increasing its capacity to absorb iron as demand rises.

But these adaptations aren’t always enough. If someone enters pregnancy with limited iron reserves, consumes insufficient iron, or has difficulty absorbing it, the growing demands of the second and third trimesters can begin to outpace the body’s available supply.

That’s why an iron level that looks perfectly adequate early in pregnancy doesn’t necessarily tell us what will be happening several months later.

Just how common is iron deficiency during pregnancy?

More common than many people realize.

In a large analysis of U.S. National Health and Nutrition Examination Survey data collected between 1999 and 2006, researchers found that approximately 18% of pregnant women had iron deficiency. What’s particularly interesting is how dramatically prevalence changed as pregnancy progressed.

These are historical estimates, and prevalence can vary depending on the population and the laboratory criteria used to define deficiency. Still, the pattern is important: iron depletion becomes considerably more common as pregnancy progresses. Globally, the World Health Organization estimated that approximately 35.5% of pregnant women had anemia in 2023, although not all anemia is caused by iron deficiency.

It’s also important to distinguish iron deficiency from iron-deficiency anemia, because they’re not the same thing.

Iron deficiency occurs when the body’s available iron supply becomes inadequate, often beginning with the depletion of stored iron. Iron-deficiency anemia develops when that shortage becomes significant enough to interfere with normal hemoglobin production.

That means someone can have declining iron stores long before their hemoglobin becomes low enough to meet the diagnostic criteria for anemia.

And this distinction is one of the biggest reasons we believe ferritin deserves more attention during pregnancy.

Ferritin: the piece of the picture we don’t always see

Ferritin is a protein that stores iron inside cells. Measuring ferritin in the blood gives us an estimate of the body’s iron reserves, making it one of the most useful markers for identifying iron deficiency.

A complete blood count, on the other hand, tells us about the blood cells themselves. It includes measurements such as hemoglobin, hematocrit, and red blood cell indices, which can help identify anemia and provide clues about its cause.

Both tests are valuable, but they’re answering different questions.

Here’s why that difference matters:

“

Ferritin can become depleted before hemoglobin falls below the normal range.

As iron reserves are used to support expanding maternal blood volume and fetal development, the body may initially maintain hemoglobin production by drawing from stored iron. Eventually, if demand continues to exceed supply, those reserves may become insufficient and anemia can develop.

Imagine entering pregnancy with a ferritin level of 45 ng/mL. A value like this doesn’t automatically indicate a problem, but it also doesn’t guarantee that iron reserves will remain adequate for the rest of pregnancy. As demands increase, ferritin may decline substantially over the following months, even while hemoglobin remains within an acceptable range.

This is also why looking at trends can be useful. A ferritin result provides information about iron stores at one point in time, while repeat measurements can help us understand how those reserves are changing as pregnancy progresses.

Ferritin isn’t a perfect standalone marker, however. It can rise in response to inflammation or infection, sometimes making iron stores appear more adequate than they truly are. Pregnancy-related changes also affect how laboratory markers are interpreted. For that reason, ferritin should be evaluated alongside the CBC, medical history, and other iron studies when appropriate.

Why we believe ferritin is worth checking every trimester

Standard prenatal care in the United States generally includes a CBC during the first trimester and another around 24–28 weeks. This is an important screening strategy that helps identify anemia during pregnancy, particularly as iron requirements increase.

However, a CBC alone may not identify iron depletion in its earlier stages. Ferritin is not universally included in routine prenatal bloodwork, and many practices reserve iron studies for patients who already have anemia, concerning symptoms, or other risk factors.

At Parenthood Wellness, we take a more proactive approach to understanding iron status. We believe that checking ferritin alongside a CBC during each trimester can provide useful information about how the body’s iron reserves are responding to the changing demands of pregnancy.

The goal isn’t to find a reason to prescribe more iron. It’s to understand whether the amount of iron someone is consuming is appropriate for their current needs.

For someone whose ferritin is declining substantially, additional evaluation and targeted iron support may be warranted before anemia develops. For someone whose iron stores are adequate and stable, those results may help avoid unnecessary escalation of supplementation. And for someone receiving treatment for iron deficiency, follow-up testing can help evaluate whether the approach is working.

There isn’t currently a universal recommendation that every pregnant person undergo ferritin testing each trimester, and stronger evidence is needed to determine whether this exact screening schedule improves clinical outcomes. Still, given how quickly iron demands change during pregnancy, we see value in using ferritin to support more individualized conversations about iron intake and supplementation.

Your baby is building their own iron stores, too

One of the most fascinating reasons iron matters during pregnancy has to do with what happens after your baby is born.

While you’re pregnant, your baby is doing more than using iron for immediate growth and development. They’re also accumulating iron reserves that will help support their needs during the first several months of life.

A significant portion of this iron accumulation occurs during the third trimester, when iron is actively transferred across the placenta and stored in the developing baby’s body. These reserves are especially important because babies grow rapidly after birth, and their developing brains and bodies continue to require iron for normal function.

Although the iron in human milk is well absorbed, the total quantity is small. Healthy, full-term babies generally rely on the iron stores they accumulated before birth, along with their ongoing dietary intake, to meet their iron requirements during early infancy. By around six months of age, those stores are often becoming depleted, and infants need additional dietary sources of iron, such as iron-rich complementary foods or supplementation when recommended by their pediatrician.

This makes the third trimester an especially important period for fetal iron accumulation. Babies born prematurely miss part of that late-pregnancy window, which is one reason they’re at greater risk for low iron stores. Maternal iron status can also influence the amount of iron available to the baby, particularly when maternal deficiency is significant.

Of course, fetal iron regulation is complex. The placenta has mechanisms that help prioritize iron transfer to the developing baby, so a mild reduction in maternal iron stores doesn’t necessarily mean the baby will be iron deficient. However, those compensatory mechanisms have limits, and maintaining appropriate maternal iron status remains an important part of supporting fetal development.

The connection between iron and your baby’s brain

Your baby’s brain begins developing very early in pregnancy, and the process continues rapidly throughout gestation and the first years of life. Iron plays a particularly important role during this period because it’s involved in several processes necessary for healthy neurological development.

For example, iron supports the production and function of neurotransmitters such as dopamine, contributes to mitochondrial energy metabolism within developing brain cells, and is essential for myelination. Myelin is the protective coating that develops around nerve fibers and helps electrical signals travel efficiently through the nervous system.

Research has linked inadequate iron availability during important developmental periods with differences in cognitive, motor, and behavioral outcomes in children. Studies evaluating maternal iron deficiency and anemia have also identified associations with aspects of offspring neurodevelopment, although findings vary and are influenced by factors such as the timing and severity of deficiency, maternal health, and the child’s postnatal environment.

It’s important to be careful with how we interpret this research. An association between low maternal iron status and a developmental outcome doesn’t mean that a particular ferritin value will predict a child’s future learning, attention, or behavior. Nor does it mean that every child exposed to lower iron availability during pregnancy will experience developmental challenges.

But the biological importance of iron during brain development is well established, and identifying and appropriately managing iron deficiency during pregnancy is one meaningful way to support both maternal and fetal health.

Iron matters for mom, too

With so much focus on supporting the developing baby, it’s easy to overlook how dramatically pregnancy changes the mother’s body.

Iron deficiency can affect energy levels, exercise tolerance, concentration, and general well-being. As deficiency progresses to anemia, symptoms may include significant fatigue, dizziness, weakness, shortness of breath, and heart palpitations. These symptoms can be especially difficult to recognize during pregnancy because some overlap with changes many women experience even when their iron status is normal.

More significant maternal anemia has been associated with adverse pregnancy outcomes, including preterm birth, low birth weight, and an increased risk of blood transfusion around delivery. Entering labor with inadequate hemoglobin can also make it more difficult to tolerate blood loss, which is particularly important if postpartum hemorrhage occurs.

I also think it’s worth considering maternal recovery after delivery. Childbirth involves blood loss, and the postpartum period places substantial physical demands on the body. Entering that stage with depleted iron reserves can make an already challenging recovery more difficult, especially if anemia develops or persists.

Supporting maternal iron status isn’t simply about preventing a low laboratory result. It’s about helping the body meet the substantial physiological demands of pregnancy, childbirth, and postpartum recovery.

More iron isn’t always better

With all this discussion about iron deficiency, it might seem logical to simply take as much iron as possible during pregnancy. But that’s not how iron works, and it’s another reason I love using laboratory testing to help guide individualized care.

Iron is essential, but excess iron can also be problematic. Because iron participates in chemical reactions that can generate reactive oxygen species, excessive amounts of available iron have the potential to contribute to oxidative stress and cellular damage.

This doesn’t mean that taking a standard prenatal vitamin containing iron is harmful. Iron supplementation during pregnancy has well-established benefits for reducing the risk of maternal iron deficiency and iron-deficiency anemia, and many prenatal vitamins contain approximately 27 mg of iron to help meet pregnancy requirements.

However, not everyone needs additional high-dose iron beyond their prenatal vitamin. Someone with substantial iron reserves may have different needs from someone who enters pregnancy with low ferritin, and those needs may change as pregnancy progresses. Higher supplemental doses can also cause nausea, constipation, and other gastrointestinal symptoms, which can be particularly frustrating during pregnancy.

Research into the potential effects of unnecessary high-dose iron supplementation in iron-replete pregnancies is ongoing. Although oxidative stress is one proposed concern, evidence of clinically important harm from routine prenatal iron intake remains limited and should not be overstated.

The key is to distinguish between meeting normal pregnancy requirements and treating a documented deficiency. When iron deficiency or iron-deficiency anemia is identified, therapeutic doses may be necessary and appropriate, even when they exceed the usual daily recommended intake. Those decisions should be made with a healthcare professional who can evaluate the broader clinical picture.

“

Our goal isn’t to maximize iron levels. It’s to maintain an appropriate iron supply for the changing needs of pregnancy.

A more individualized approach to iron during pregnancy

What I find so valuable about monitoring iron throughout pregnancy is that it helps us move away from a one-size-fits-all approach.

Two women can be at the same stage of pregnancy, take the same prenatal vitamin, and have very different iron needs. One may begin with strong iron reserves and maintain them throughout pregnancy, while another may enter pregnancy with low ferritin following years of heavy menstrual bleeding, dietary insufficiency, or a recent pregnancy.

Those differences matter, and laboratory testing can help us understand them.

At Parenthood Wellness, our philosophy is to look at iron status as something that can evolve throughout pregnancy rather than treating it as a single measurement taken early on. By following ferritin and the CBC across each trimester, we can better understand whether iron reserves are declining, whether supplementation is adequate, and when additional medical evaluation may be warranted.

This approach complements, rather than replaces, standard prenatal care. Your obstetrician or midwife remains responsible for diagnosing and managing pregnancy complications, including iron-deficiency anemia, and iron supplementation should always be coordinated with your prenatal provider.

The bigger picture

Pregnancy asks the body to do something extraordinary. Over the course of nine months, your circulation adapts to support an entirely new life, your baby develops a complex nervous system, and essential nutrients are transferred across the placenta to support growth and prepare for life after birth.

Iron is woven into nearly every part of that process. It’s necessary for healthy oxygen delivery, maternal red blood cell production, fetal development, and the accumulation of iron reserves that help carry your baby through the first months of life.

And because iron requirements change so dramatically throughout pregnancy, understanding your status early on doesn’t necessarily tell us what your body will need later.

That’s why we believe ferritin deserves a place in the conversation throughout pregnancy. Not because every woman needs more iron, but because

“

every pregnancy is different, and having more meaningful information can help us make more thoughtful decisions.

At Parenthood Wellness, we believe that thoughtful monitoring, individualized support, and strong nutritional foundations can help families navigate pregnancy with greater understanding and confidence.

Because supporting your baby’s development and caring for your own health should always go hand in hand.