Iron Infusions in Pregnancy

Iron deficiency is incredibly common in pregnancy, and more women are being offered iron infusions than ever before, in some cases almost as routinely as oral supplements. But should they be? Infusions can rapidly correct anaemia, yet they don’t always align with the body’s natural physiology, and they carry real risks.

This blog explores when iron infusions are necessary, when they aren’t, who should avoid them, and how to support healthy iron levels naturally before and during pregnancy.

Pregnancy naturally changes how iron looks on blood tests. Because plasma volume expands by up to 50%, haemoglobin levels drop, which is a normal, adaptive change called physiological anaemia of pregnancy (Frayne et al., 2019). This does not mean the mother is truly iron deficient.

It’s important to distinguish between the following:

1.     Physiological Anaemia of Pregnancy

·       Haemoglobin is slightly lower due to blood dilution from 20 weeks’ gestation onwards

·       Ferritin and iron stores may still be normal

·       No IV iron is needed because this is a natural adaptation to support blood flow to the placenta and baby. IV iron in cases of physiological anaemia is not just unnecessary, but potentially harmful because it bypasses natural regulation.

2.     Iron Deficiency Without Anaemia

·       Ferritin (iron storage) is low, but haemoglobin is still within range

·       Common in women with iron deficiency before conception

·       Infusions are not appropriate here because the deficiency is correctable with dietary, lifestyle and supplemental support

3.     Iron Deficiency Anaemia

·       Both ferritin and haemoglobin are low

·       This is where symptoms start to appear and where treatment matters most

·       When all other avenues of diet, lifestyle and oral iron supplements have been applied, a consideration to do IV iron might be discussed with your maternal care provider

4.     Anaemia of Chronic Disease or Inflammation

·       Inflammatory states (e.g. autoimmune disease, infections, gut inflammation) raise hepcidin, blocking iron absorption and trapping iron in storage

·       Ferritin may look normal or even high, but iron is not being utilised properly (Zhuang et al., 2014)

·       This is why testing inflammatory markers like CRP can give us a whole picture of iron and able us to distinguish between the different iron deficiency terms, so appropriate treatment is used

·       In this case, IV iron won’t solve the issue because the block is regulatory, not due to lack of supply

Why I Don’t Recommend Iron Infusions in Pregnancy

As discussed during pregnancy, plasma volume expands significantly, which naturally lowers haemoglobin concentration, this is a normal change known as physiological anaemia of pregnancy (Frayne et al., 2019). At the same time, the placenta actively prioritises iron transport to the baby, even when the mother’s stores are low.

Iron infusions bypass these natural checks and balances by delivering a rapid iron load that the body may not be equipped to process.

Infusions deliver large amounts of iron in one sitting (sometimes 1000–2000mg within 15 minutes). Compare this to your standard iron supplement which is 24mg daily dosage.

You might be asking why iron infusion over oral iron?

Some maternal care providers favour iron infusions, especially in settings where oral iron supplementation is perceived as ‘less effective’. This is important to unpack because a comprehensive systematic review and meta-analysis published in Blood analysed data from multiple randomized controlled trials comparing intravenous (IV) iron to oral iron supplementation in pregnant women with iron deficiency anemia (IDA). The study found no significant difference in maternal and neonatal outcomes between the two treatment methods (Sachdeva et al., 2024).

Further to this, large studies (SMFM, 2025) show IV iron raises haemoglobin faster, but outcomes on birthweight, preterm birth, and maternal wellbeing are not consistently superior compared to oral supplementation.

Another argument is that infusions provide a quick and direct method of replenishing iron stores, which may be appealing in cases where patients have difficulty adhering to oral supplementation regimens. And whilst this is true, they aren’t without risk.

Potential Immediate Risks

·       Muscle aches, fever, nausea, headaches, dizziness

·       Permanent skin staining at the injection site

·       Anaphylaxis (3.6 per 1,000 women)

Potential Medium to Long Term Risks

·       Iron overload: ferritin can spike to 400 µg/L and remain high for months after a single infusion (consider that ferritin above >150 µg/L to >200–300 µg/L, depending on the guideline you follow is considered overload in women)

·       Oxidative stress: excess iron drives free radical activity

·       Infection risk: iron overload suppresses immune response and can increase bacterial virulence

·       Hypophosphataemia: particularly with carboxymaltose infusions, leading to bone weakness, low vitamin D, and impaired phosphate metabolism

·       High haemoglobin post-infusion: associated with preterm birth, perinatal death, low birthweight

·       Research published in Nutrients indicates that high doses of iron supplementation can induce lipid peroxidation and DNA damage, which may impair insulin secretion and contribute to gestational diabetes (Zhuang et al., 2014)

·       A review in Longdom highlights that adverse maternal outcomes, including preeclampsia, have been linked to iron overload during pregnancy (Delahunty et al., 2024)

Large trial datasets and observational series included in reviews (thousands of pregnancies across multiple IV formulations in the 2nd/3rd trimester) have not shown a consistent increase in neonatal mortality or common complications directly attributable to iron infusions but the reviews stress many trials were small, heterogeneous, and focused on haematologic endpoints rather than long term infant health (Sachdeva et al., 2024).

Because of the risks, the lack of proven benefit in outcomes for mothers and babies, and the frequent misapplication of iron infusions outside of true deficiency anaemia, I do not confidently recommend them to clients.  

Who May Benefit with an Iron Infusion as a Last Resort

Whilst I cannot confidently recommend iron infusions in pregnancy, I also cannot confidently recommend iron deficiency anaemia in pregnancy.  

Too much iron can be just as harmful as too little. Research shows a U-shaped relationship:

·       Too little iron can lead to anaemia, fatigue, poor oxygen delivery, impaired foetal development, increase risk of post-partum haemorrhage

·       Too much iron can lead to oxidative stress, tissue damage, gestational diabetes, preeclampsia, and poor perinatal outcomes

The only scenario in which I would consider an iron infusion is for severe and true iron deficiency anaemia late in pregnancy, when oral iron has not been effective and there is limited time before delivery.

In my experience, this situation often arises because maternal care providers do not monitor iron status frequently enough. Waiting until the standard 28 week check is problematic, as research and clinical experience show that many women’s iron levels can drop significantly much earlier (sometimes as early as 13–20 weeks).

Who Should Avoid Iron Infusions Completely

·       First trimester women: IV iron is contraindicated before 16 weeks due to lack of safety data

·       Women with normal ferritin but low haemoglobin: This may indicate another type of anaemia (e.g. B12 deficiency, folate deficiency, or anaemia of inflammation). An infusion will not correct the underlying issue and may delay proper diagnosis

·       Women with autoimmune conditions: Iron overload can worsen inflammation and immune dysregulation

·       Women with already high iron stores: Ferritin >150 µg/L suggests risk of overload. An infusion here can trigger oxidative stress, infection risk, and tissue damage

Understanding Iron Testing in Pregnancy from a functional perspective

In my clinical experience working with mothers in pregnancy, so commonly I see ferritin alone being tested and you can see from the above how much more information we are missing and how harmful it could be if used without a complete picture of iron within the body.

What to Request

·       Full iron studies (not ferritin alone like commonly prescribed by maternal care providers)

·       Haemoglobin

·       CRP (C-reactive protein) to check if inflammation is skewing ferritin results

When to request it

·       Preconception: 3 months before conceiving, to identify and treat deficiencies early (some studies suggest that women with ferritin below 70 µg/L are more likely to develop iron deficiency anaemia during pregnancy or postpartum Banerjee et al., 2024).

·       During pregnancy: 12, 20, 28, and 36 weeks’ gestation

Why Testing Matters

·       Prevents unnecessary infusions

·       Detects early declines before they become severe

·       Distinguishes iron deficiency anaemia from other causes (e.g. B12 deficiency, anaemia of inflammation)

Optimising Iron Before and During Pregnancy

Prevention is better than infusion. Building strong iron stores before conception makes pregnancy smoother and reduces the likelihood of anaemia.

Preconception Strategies

·       Diet rich in bioavailable iron and essential cofactors like B12, zinc, and copper which help regulate iron transport and red blood cell production

·       Support gut health for optimal absorption: inflammation, dysbiosis, low stomach acid, and celiac/IBS-like symptoms can impair iron uptake.

·       Supplementing if needed (with practitioner guidance)

During Pregnancy

·       Continue nutrient dense foods (3–4 serves red meat/week, vitamin C rich foods, essential cofactors)

·       Use well formulated practitioner supplements if diet alone isn’t sufficient. Look for iron bisglycinate as a highly bioavailable and gentle form of iron for your stomach (not constipation causing)

·       Test regularly, iron levels can decline rapidly as pregnancy progresses

·       Be proactive, not reactive: correcting deficiency early avoids the need for infusions

Resources: 

Banerjee, A., Athalye, S., Shingabe, P., Khargekar, V., Mahajan, N., Madkaikar, M. (2024). Efficacy of daily versus intermittent oral iron supplementation for pregnant women with iron deficiency anaemia. eClinicalMedicine, 54, 101774. https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(24)00321-3/fulltext

Delahunty, M., Sadek, B., & Yerigeri, K. (2024). Maternal-fetal outcomes of hemochromatosis and iron supplementation in pregnancy. Journal of Clinical & Experimental Cardiology, 15, 880. https://www.longdom.org/open-access-pdfs/maternalfetal-outcomes-of-hemochromatosis-and-iron-supplementation-in-pregnancy.pdf

Frayne, J., & Pinchon, D. (2019). Anaemia in pregnancy. Australian Journal of General Practice. The Royal Australian College of General Practitioners. https://www1.racgp.org.au/ajgp/2019/march/anaemia-in-pregnancy.

Journal of Nutrition. (2022). Iron and oxidative stress in pregnancy. The Journal of Nutrition. Retrieved from https://jn.nutrition.org/article/S0022-3166(22)15930-4/

Sachdeva, A., Manuel, P., Kishibe, T., Fralick, M., Kuderer, N. M., Tang, G., & Sholzberg, M. (2024). Is it safe to correct iron deficiency anemia with intravenous iron in pregnancy? A systematic review and meta-analysis. Blood, 144(Supplement 1), 5262. https://ashpublications.org/blood/article/144/Supplement%201/5262/526800/Is-It-Safe-to-Correct-Iron-Deficiency-Anemia-with.

SMFM. (2025). Large study finds IV iron treatment during pregnancy safe and effective for anemia. Society for Maternal-Fetal Medicine. https://www.smfm.org/news/large-study-finds-iv-iron-treatment-during-pregnancy-safe-and-effective-for-anemia

Zhuang, T., Han, H., & Yang, Z. (2014). Iron, oxidative stress and gestational diabetes. Nutrients, 6(9), 3968–3980. https://www.mdpi.com/2072-6643/6/9/3968