Ferritin and fertility: correcting low iron roughly doubled live birth

The study

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.

Methodology

• Each woman with ferritin under 30 was given one 500 mg intravenous ferric carboxymaltose infusion (Ferinject®)
• 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.
• The study did not report the average time from the infusion to conception. It re-checked ferritin on average 110 days (about 3.7 months) after the infusion, and conception followed in the treatment cycles after that.
• The analysis accounted for other factors that could influence pregnancy outcomes. For live birth, these were age, embryo genetic testing (PGT-A), and whether repeated iron infusions were required. For miscarriage, the analysis accounted for age, the reason for infertility, and the woman’s total number of pregnancies.

What they found

Correcting iron roughly doubled the live birth rate

Live birth went from 25% 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.

Needing a second or third infusion meant lower odds of a live birth

Women who needed more than one infusion had a 43% reduction in their odds of live birth compared with women who needed only one infusion. The authors suggest a fairly straightforward explanation: women who needed repeated infusions may have had greater or ongoing iron loss, meaning the standard 500 mg dose of ferric carboxymaltose was not enough to fully correct their deficiency. In practical terms, this does not mean that receiving extra iron caused poorer fertility outcomes. More likely, needing repeated infusions identified a group with more severe or harder to correct iron deficiency, possibly because of ongoing blood loss, poor absorption, or conditions such as endometriosis.

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.

Another limitation is the substantial increase in ERA use (8% before vs. 34% after infusion), which could confound implantation and live-birth outcomes but was neither adjusted for nor discussed as a limitation. A further limitation is that the “unexplained infertility” group included women with social infertility (that is, were in homosexual relationships), making this subgroup clinically heterogeneous and harder to interpret.

Things you could 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 and citizen researcher. Infertility diagnosis at 36, two children via IVF (first at 37 and second at 41). Leveraged research to shift euploidy rate at age 40 from average 43 year old to average 25-30 year old.

✓Reviewed for accuracy by Dr. Rida Asghar, MBBS, Resident Medical Officer (BS-17) OBGYN, Women & Children Teaching Hospital, Gomal Medical College