Do All Pregnant Women Need To Take Iron Supplements?

As you are likely experiencing, pregnancy can feel a little overwhelming, especially when it comes to how to support your health and your baby’s. So today, I wanted to chat a little bit about the importance of iron during pregnancy. 

Now, we know that during pregnancy there is an immense amount of fetal growth and development. However, although we may assume our body is just “built for this”, this growth requires major changes in your biological, chemical and physiological state. In fact, your maternal nutritional and metabolic status can have a significant impact on the development and growth of your baby and can also lead to epigenetic changes that can impact gene expression. These changes can be beneficial to your child or can increase the risk of disease development during a child’s life, both during childhood, but also during adulthood.

So, what is iron and do all pregnant women need to take an iron supplement? 

Iron is a mineral needed for growth and development, not only to help grow a baby but, also for your own health as well. In fact, our body uses iron to make hemoglobin, which is a protein found in red blood cells that allows us to carry oxygen from the lungs to all parts of our body. Iron also helps support myoglobin production, a protein that provides oxygen to our muscles. And although we naturally find iron in the red blood cells of our bloodstream, iron is also stored in the body in the form of ferritin. Ferritin is found most commonly in the liver, spleen, muscle tissues and bone marrow. Ferritin is delivered throughout the body by a protein known as transferrin. This is important because in order to properly assess someone's iron status, we must take into consideration both their serum iron, as well as, ferritin status. 


During pregnancy, our need for iron increases, primarily to supply the growth of the growing baby and the placenta. Iron is also necessary for fetal brain development. Unfortunately, without proper iron intake, pregnant women are more susceptible to experiencing iron deficiency anemia. In the United States alone, it is estimated that about 19% of pregnant women will experience some form of iron deficiency anemia during their pregnancy. Of those who experience iron deficiency anemia during pregnancy, about 7% are diagnosed during their first trimester while about 30% will be diagnosed during their third trimester. 

These high rates of iron deficiency seen in pregnancy is also the reason your prenatal should generally contain between 30-60mg of elemental iron, as recommended by the WHO. This is also important to mention because the amount of iron you need during pregnancy may not be met with a standard multivitamin. Instead, looking for a high quality prenatal will most likely be more beneficial. Now although we do get iron from food, it is estimated that in the United States, pregnant women will consume only about 17mg/day of iron, resulting in about 36% of pregnant women consuming less than the requirement daily dietary intake of iron. This means that even in a developed country like the United States, supplementing with a high quality prenatal is often necessary. 

Dietary Sources of Iron

There are two dietary forms of iron; heme and non-heme iron. The most bio-available form found in food is heme iron, which is most commonly found in meat, poultry and fish. Non-heme iron, which comprises about 60% of the iron in animal foods and all of the iron in plant foods is less bio-available and less easily absorbed, which would also explain why those who are vegan or vegetarian, are more at risk of developing iron deficiency anemia. 

It is also important to know that iron absorption can be inhibited by certain foods including: phytates in whole-grain cereals, calcium and phosphorus in milk, tannin in tea and polyphenols in many vegetables. These particular foods specifically decrease the absorption of iron by decreasing the intestinal solubility of nonheme iron from your meal. The addition of even relatively small amounts of meat and ascorbic acid (vitamin-C) containing foods can substantially increase the absorption of iron. 

Symptoms of Iron Deficiency Anemia During Pregnancy

  • Pale skin, lips and nails. 

  • Fatigue 

  • Weakness 

  • Dizziness or lightheadedness 

  • Shortness of breath 

  • Craving or chewing ice

Are all iron supplements the same? 

The short answer is, no. The absorption of iron supplements is largely influenced by the type of iron used, the timing of dosing, and whether or not the iron is given alone or as part of a vitamin-mineral supplement. When determining the dose of iron supplements, the label on the bottle can be a little deceiving. For example, a 300mg tablet of ferrous iron sulfate, doesn’t actually contain 300mg of active iron, it contains about 60 mg of active iron. Most ingredient lists should list the amount of active iron provided with each dose. Studies have also found that iron tablets (other than slow release formulas) are generally more readily absorbed between meals rather than with meals. This is important to mention because most prenatals will contain instructions that tell you to take your prenatal with food. This is where in patients with iron deficiency anemia, a prenatal or even multivitamin supplement, may likely not be the best way to correct their iron deficiency anemia and instead, they may benefit from a single sourced form that can be taken on its own. I wouldn’t advise taking your prenatal on an empty stomach because prenatals do contain a high amount of B-vitamins that may cause nausea if taken without food. Instead, if you have been diagnosed with iron deficiency anemia, a separate iron supplement may be favored. 

What are the side effects of taking iron supplements? 

Although iron is necessary in pregnancy, iron supplements can cause a few important side effects including constipation, dark stools, stomach upset and heartburn in some cases. If you are already struggling with constipation during your pregnancy, please note taking iron supplements may make your symptoms worse. In some cases, where iron deficiency is severe, your doctor may recommend iron IV infusions as a better alternative. It is also extremely important to keep your iron supplements away from small children, as accidental overdose of iron-containing products is a leading cause of fetal poisoning in children 6 years or younger. Keep iron containing supplements out of the reach of children and in case of accidental overdose, call a doctor and poison control center immediately. 

About the Author: Meet Dr. ZenAlissia Zenhausern- Pfeiffer, NMD, FABNE, (commonly known by her patients as Dr. Zen), is a licensed naturopathic doctor board certified in naturopathic endocrinology and the founder of NMD Wellness of Scottsdale, a premier naturopathic medical practice that focuses on helping women to take a proactive approach to their hormone and fertility health. Dr. Zen has been featured as a lead expert in Forbes, Shape Magazine, and Instyle and is deeply passionate about bridging the gap between traditional and natural medicine in the world of fertility. She works with a variety of hormone related issues including PCOS, endometriosis and unexplained infertility. Her goal is to help more women get back into the driver’s seat of their own health to make lasting transformational changes to their health to bring more cute and adorable babies into this world. Read More About Dr. Zen...