When a woman finds out she’s pregnant, the first recommendation a doctor usually gives is to take a prenatal vitamin.
Prenatal vitamins contain essential nutrients like folate, vitamin B12, vitamin A, etc. They are recommended to prevent nutrient deficiencies during pregnancy, because even mild deficiencies can interfere with fetal development, increase the risk of complications, and affect the long-term health for both mother and baby. During pregnancy, a woman’s nutrient needs dramatically increase because her body is undergoing intense physiological changes.
Blood volume expands by up to 50%, placing higher demands on iron, B vitamins, and protein. The developing baby draws on the mother’s stores of calcium, magnesium, and other minerals to build bones, organs, and the brain. Metabolic rate increases, hormone levels shift, and the body’s need for antioxidants, methylation support, and oxygen-carrying capacity all rise.
Iron is one of the most emphasized nutrients in prenatal supplements because blood volume increases during pregnancy. This raises her need for iron to support red blood cell production and oxygen transport to the baby.
The Recommended Dietary Allowance (RDA) for iron during pregnancy is 27 mg per day, and most prenatal vitamins meet or exceed that amount, often containing up to 30–50 mg. But this assumes the woman isn’t getting iron from her diet, which is rarely the case. Iron is already added to a wide range of processed foods.
Most flours, cereals, and grain products in the U.S. are fortified with iron, so many women may be getting additional iron from multiple sources without realizing it.
On top of this, estrogen increases iron absorption. When pregnant, the higher estrogen levels cause them to absorb about nine times as much as men (Peat, 2006). This is the body’s natural way of preparing for the increased demands of pregnancy.
However, this also means that iron overload can become a real risk, particularly when combined with high-dose supplementation or iron-fortified foods.
Excess iron can promote oxidative stress, feed pathogens, and contribute to complications like gestational hypertension, inflammation, and altered fetal development. So, for women without iron deficiency or anemia, high-dose iron supplementation may not be necessary and could do more harm than good.
Both too little and too much iron during pregnancy may pose risks: “Two cohort studies have confirmed a U-shaped risk curve of maternal hemoglobin, reflecting a higher risk of adverse pregnancy outcomes among women with highest or lowest hemoglobin concentrations in pregnancy” (Cassel et al., 2021).
Researchers found that elevated maternal iron levels were associated with:
- Reduced infant length-for-age at six months.
- Lower cognitive scores in infants at six months.
- An increased risk of childhood Type 1 diabetes
Some prenatal supplements contain both omega-3 fatty acids (like DHA and EPA) and high levels of iron in a single capsule. But, combining them in one formula can create a chemical problem.
Omega-3 fatty acids are chemically fragile and highly prone to oxidation. Iron, especially in its free or unbound form, acts as a pro-oxidant: it triggers reactions that generate free radicals, which can break down delicate fats like DHA and EPA, both during manufacturing and after ingestion.
When omega-3s oxidize, they can become harmful. Oxidized fats generate inflammatory byproducts and increase oxidative stress.
This added oxidative burden can interfere with nutrient delivery to the baby, disrupt hormone balance, and strain the body’s antioxidant defenses at a time when they are already in high demand.
So, what should women do?
Check thyroid health. Thyroid hormone needs increase by up to 30–50% during pregnancy, especially in the first trimester. A well-functioning thyroid supports red blood cell production and helps prevent anemia—not just iron. Low thyroid function can mimic iron deficiency, so getting a full thyroid panel (including TSH, Free T3, Free T4, and thyroid antibodies) is a smart starting point.
Ensure adequate copper and zinc intake. These two minerals are often overlooked but are essential for regulating iron metabolism. Copper is needed to move iron through the body (via the protein ceruloplasmin), while zinc helps balance absorption. Deficiencies in either can lead to functional iron issues, even if your iron levels appear normal.
Swap fortified grains for real sources of bioavailable iron. Many packaged cereals, breads, and flours are fortified with synthetic iron that’s harder to absorb and may irritate the gut. Red meat and organ meats offer heme iron, the most bioavailable form, and come with the necessary cofactors like B12 and zinc to support healthy blood building.
Avoid prenatals with both iron and omega-3s in the capsule. If your labs don’t show iron deficiency, it may be better to avoid prenatals that combine iron and DHA, as this combo can lead to oxidation and reduce the quality of both nutrients. We should only supplement iron if and when it’s truly needed.
The most important thing women can do is to eat well. The best foundation for a healthy pregnancy is built on nutrient-dense whole foods, clean water, sunshine, deep rest, and low stress:
- Milk and cheese for calcium, vitamin K2, and vitamin B2
- Red meat for B-vitamins, heme-iron, zinc, taurine, etc.
- Eggs for choline, selenium, vitamin D
- Liver (in moderation) for folate, bioavailable vitamin A, copper, and CoQ10
- Bone broth and gelatin for glycine, proline, and collagen to support connective tissue, skin, and gut health
- Fruits and vegetables for easily digestible carbohydrates, potassium, and antioxidants
- Seafood (low in mercury) for iodine, zinc, and selenium
In a perfect world, nutrient demands would be met through diet. Unfortunately, many pregnant women are not meeting nutrient needs. And today, more women are exposed to stressors that increase those demands even further. Prenatal supplementation has become a safety net.
Iron is a really common nutrient in many prenatal vitamins, but more isn’t always better. While it’s important for supporting the increased blood volume and growth that happens during pregnancy, not every woman needs high doses. These supplements are often given without considering what a woman is eating or evaluating her actual iron status. In some cases, excess iron can lead to digestive issues, gut imbalances, and added oxidative stress, and iron overload during pregnancy has been linked to health problems in offspring later in life.
The foundation for a healthy pregnancy starts with the basics: nutrient-dense food, clean water, rest, sunshine, and low stress. Supplements can absolutely play a helpful role, but the quality, form, and individual fit matter. Some women may need iron, while others don’t. Pregnancy is a critical time and what we take can have lasting effects on both mom and baby. Being informed and intentional about what we put into our bodies during this time is important.