Study Summary
3 minute readIron is needed for the ovaries, for the lining of the womb and for a growing pregnancy. Still, low iron is a commonly overlooked aspect of fertility. The usual approach only flags iron as a problem once both ferritin and haemoglobin levels are low. This study, however, looked at women with infertility whose ferritin was low (30 or under) regardless of their haemoglobin status, then gave them a single iron infusion and compared their results before and after.
After the infusion, the share of women who conceived rose from 65% to 77%, the live birth rate went from 26% to 51%, and the miscarriage rate fell from 28% to 13%. After adjusting for age and other factors, correcting the iron deficiency was linked to more than three times the odds of a live birth and about a two-thirds lower chance of miscarriage.
- Hypothesis: that treating iron deficiency (that is, ferritin at 30 or under, regardless of haemoglobin status) with an iron infusion improves conception, live birth and miscarriage rates in women with infertility.
- Study Type: a retrospective before-and-after study of 292 women under 43 with iron deficiency who were trying to conceive using fertility treatments (IUI and IVF), each compared with her own results before the infusion. Using each woman as her own comparison is useful, but with no untreated control group, time and other changes can also play a part, so it shows a strong association rather than causation.
- Conclusion: fixing low ferritin, even when haemoglobin was normal, was linked to markedly higher conception and live birth and much lower miscarriage.
Try it with a result
Pick an outcome to see the before and after the single iron infusion. The comparison is each woman against her own earlier result, not a separate control group.
The study
This study recorded conception, live birth and miscarriage before and after the iron infusion.
Study population
292 women under 43 years old, doing IUI and IVF, with a history of infertility and a current iron deficiency (defined as ferritin at 30 micrograms per litre or under) were included. In general, the women had average BMI and average AMH levels.
Anyone with infertility whose ferritin is 30 or under, including women whose haemoglobin and standard iron levels look normal, since ferritin can be low while those are still in range.
If your ferritin is already over 30, topping it up further was not shown to help.
Methodology
- Each woman's conception, live birth and miscarriage results after the iron infusion were compared with her own results before it, drawn from the clinic's records. Ferritin was measured before and after to confirm the stores had actually been replenished.
- The main analysis then adjusted for age, whether genetic testing of embryos was used and whether more than one infusion was needed, so the iron effect is estimated after allowing for those.
What they found
Correcting iron roughly doubled the live birth rate
Live birth went from 26% before the infusion to 51% after, and conception from 65% to 77%. In the adjusted model, treating the deficiency was linked to more than three times the odds of a live birth.
Miscarriage rates were more than halved
The miscarriage rate fell from 28% to 13%, and the adjusted odds of miscarriage were about two-thirds lower. So iron seemed to act on both getting pregnant and staying pregnant.
Ferritin is the key, regardless of haemoglobin
The women were selected on their ferritin being at or below 30, irrespective of normal haemoglobin. A normal blood count does not rule out low iron stores, and ferritin is the test that catches it.
What it means for older women
Iron deficiency is common across women of all reproductive ages, driven mostly by monthly blood loss, diet, and previous pregnancies or losses, and this study did not find that it impacted older women more. The reason it matters for older women is that the effect held after adjusting for age, and it acts on the two things that get harder with age anyway, implantation and miscarriage.
For an older woman where every embryo counts, correcting a low iron level is one concrete way of giving each transfer the best chance at succeeding.
Evidence strength
The effect sizes are large across conception, live birth and miscarriage, but there is one thing the paper glosses over. The headline miscarriage figure (odds 0.32) comes from a simpler model; once every other factor is accounted for, the miscarriage benefit shrinks and loses statistical significance (odds 0.52, not significant), while the live birth benefit holds up in both models (odds 2.98 to 3.19). The study is also retrospective and before-and-after, with no untreated control group, and it was funded in part by the maker of the iron infusion (Vifor Pharma). The findings are strong enough to justify checking ferritin and treating a deficiency that matches the study criteria, and not strong enough to treat iron as a cure or to suggest an iron infusion in women whose ferritin is over 30.
Things you can discuss with your doctor
- If your ferritin is 30 or under, discuss correcting it before a transfer with your doctor. In some countries such as Australia this can start with a free (bulk-billed) test through a GP (family physician).
- Know that correction takes time: oral iron or an infusion needs weeks to lift your stores, so if your doctor agrees, build it into your transfer timeline rather than leaving it to the last minute.
- Don't assume normal iron or normal haemoglobin means normal ferritin, because this study's benefit was in women selected on ferritin.
Source: Tulenheimo-Silfvast A, Tiitinen A, Vuento M, et al. Iron deficiency and the effect of iron supplementation on fertility outcomes in women with infertility. Acta Obstet Gynecol Scand, 2025.
Written by
Michelle Bourke
Founder of Better IVF. I went through IVF over 38 myself, and I write these guides to be the clear, properly-sourced resource I wish I'd had, more honest than the forums and deeper than the clinic pages.