Be Careful About Iron Supplementation in Pregnancy

This is a question that comes up a lot in pregnancy. . .”What kind of iron supplements should I be taking? My practitioner says I’m anemic.” It turns out that a lot of practitioners mistakenly diagnose anemia based on old information and lack of understanding of the physiology of the pregnant woman.

This information from Dr. Michel Odent is very helpful:

    Question for Dr. Michel Odent:

My hemoglobin is now 11.4 in week of gestation 19. A friend of mine has 7.8. Do I have to take ferrum? Is there a hemoglobin-limit?

    Answer from M. Odent

It is probable that from now on your hemoglobin concentration will decrease. The placenta – which is ‘the advocate of the baby’ – will send you hormonal messages so that you dilute your blood in order to make it more fluid. Your blood volume will increase dramatically (up to 40% to 50%). Although you’ll still have the same amount of hemoglobin available, its concentration in your blood will be lower if the placenta is working well. The most authoritative published study on this issue involved more than 150 000 thousands births (Steer P, Alam MA, Wadsworth J, Welch A. Relation between maternal hemoglobin concentration and birth weight in different ethnic groups. BMJ 1995; 310: 389-91). According to this huge study a hemoglobin concentration between 8.5 and 9.5 during the second half of a pregnancy is associated with the best possible birth outcomes. Furthermore, when the hemoglobin concentration fails to fall below 10.5 there is an increased risk of low birth weight, premature birth and pre-eclampsia.

The regrettable consequence of misinterpreting this test is that, all over the world, millions of pregnant women are wrongly told that they are anemic and are given iron supplements. There is a tendency both to overlook the side effects of iron (constipation, diarrhea, heartburn, etc.) and to forget that iron inhibits the absorption of such an important growth factor as zinc. Furthermore, iron is a powerful oxidative substance that can exacerbate the production of free radicals. The disease pre-eclampsia is associated with an ‘oxidative stress’. Pregnant women need antioxidants (provided in particular by fruit and vegetable) rather than oxidative substances.

You should print the abstract of the study I mentioned (you’ll find it via PubMed, for example) in order to be in a position to discuss with practitioners who might tell you that you are anemic and that you need iron supplements. Don’t take iron supplements as long as your iron deficiency has not been proven by specific tests (ferritin in particular).

I cannot comment on the hemoglobin concentration of your friend, first because I don’t know if she is at the beginning or at the end of her pregnancy, and also because data regarding her lifestyle and data provided by a clinical exam should prevail upon the results of one laboratory test; this test should probably be repeated and completed, according to the context. (end of Dr. Odent’s comments)


Here is the link to the study he talks about:

This study is another piece of the puzzle that more women should know about:

University of Turin researchers have found that women who take iron
supplements during mid-pregnancy have a higher risk of gestational diabetes,
hypertension and metabolic syndrome. The study assessed iron
supplementation, along with other factors, for 1000 women-half with
gestational diabetes and half with normal glycemic levels-between 24 and 28
weeks gestation. Of the women studied, 212 were taking iron supplements,
mostly in the form of ferrous sulphate.

The researchers concluded, “Routine iron supplementation in pregnancy is a
matter of controversy and debate. The increasing reporting of harmful
effects for unnecessary iron supplementation should be carefully considered.
Further studies on larger cohorts are warranted to confirm these results,
but glucose values should at least be monitored in iron-supplemented
pregnant women.”

The full report can be accessed online at:

– American Journal of Obstetrics and Gynecology, 201(2): 158.e1-6, 2009

12 thoughts on “Be Careful About Iron Supplementation in Pregnancy

  1. This is why I completely reject all man-made supplements (including Floradix and Spatone) in favour of Spirulina. It is a whole food and has minerals (including iron and iodine), vitamins (including the full range B vitamins and folate) and protein. It is highly absorbable (without the gastrointestinal symptoms) and what you don’t need doesn’t accumulate, because all the micronutrients work in concert with each other. If a woman is symptomatic with anaemia (dizziness, short of breath, fatigue, racing heartbeat) I do recommend at least 10 grams of Spirulina (powder or tablets) daily which generally helps quickly. However, whereas haemoglobin can increase within days, the increase of iron stores (indicated by ferritin levels) needs to be worked on for weeks and months at a time. While I think we over-diagnose anaemia greatly, I am always watchful because if a woman is anaemic when she is lactating, it can affect milk supply over the long term, apart from the danger of postpartum haemorrhage and slow recovery from the birth when iron levels are too low.

    • Spirulina isn’t the way to go either though, algae is spore-based and scum of the earth but everything is going spore-based so I doubt my warning means anything. Why not use alfalfa or other great herbs instead that are seed-based.

  2. Hello, I came across your wonderful website through a friend’s social media network. I haven’t taken a pregnancy test yet, my period isn’t due for another week. I do, however, feel the changes happening in my breasts, abdomen and have been nauseous. I’ve started taking pre-natal vitamins as suggested by a friend who is a mother. I will be seeing my doctor next week. In the meantime, is it a good idea to take pre-natal vitamins? There are 28 mg of iron in each tablet. I eat an organic diet which includes leafy greens, and proteins such as red meat and chicken. Thank you for your time.

    • The problem with all supplements is that the nutrients (which may be synthetically produced) are all jumbled in together. This means that, even though there might be a lot of iron, it might not be absorbed well because of the presence of calcium, for example. This is why I prefer (by far) that pregnant women get their nutrients from whole foods, where the micronutrients are in balance and are in a form which is more easily utilised by the body. SO source your food well – organic (if possible), whole, unprocessed and fresh. Plenty of greens and coloured vegies. Lots of water. That’s it!

  3. Hi Gloria

    am from Vancouver but recently moved to Montreal with my fiance and became pregnant. I am having a difficult time connecting with a midwife here as services are limited. I was wondering if you knew of any midwives in Montreal who might be willing to take me on, or any doula’s that you would recommend.


  4. I have always had an issue with absorbing iron (ferritin levels are extremely low) I have been having iron injections for years under care of a dr and naturopath. Through out my pregnancy I have still followed my routine injections and in between corses really good highly bioavailable iron tablets.
    Just wondering what your thoughts are on iron injections and if there is anything I should be checking on inperticular.

  5. Hi there,
    I am so confused.. It seems that if I don’t take iron supplements I get to the point I can’t do every day life because I’m so drained. My last pregnancy I didn’t take them and ended up being dangerously low after my cesarean.. This time I started out taking a natural supplement but felt nauseous and was told the supplement needs to be in a release form. . . I was taking 4 a day since they only contain a quarter of the iron of the prescribed one. I then tried the prescription one (ferrograd) rather reluctantly.. I’ve been slightly nauseated for the last 5 days but was increasing in energy slowly… until today I just feel like I’ve crashed again. I feel queasy, have diarrhea, no appetite, low energy, irritable, breathless and light headed. I’m also breastfeeding and trying to maintain a reasonable level of exercise.. both seem to contribute to draining iron more. I feel like either way it’s catch 22 and don’t want to end up how I was after my last birth, especially with 3 kids. Do you have any suggestions as google is no help so far!



    • Are you in the UK, Milly? I looked up Ferrograd online and it appears to be a form of ferrous sulphate. Prenatal vitamins should be either ferrous fumerate or ferrous gluconate. Ferrous sulphate can make you have all those symptoms.

    • Ferrous sulfate is very poorly absorbed and is prescribed at high doses. If you’re taking a more natural iron supplement, you will need a much lower dose, and you should not exceed the dosing on the package label without consulting a knowledgeable and experienced healthcare professional who understands dosing of different forms of iron and can apply that information to your individual situation.

Leave a Reply

Your email address will not be published. Required fields are marked *