IV iron tied to higher risk of adverse perinatal outcomes in women with maternal IDA

In a study presented at SMFM 2026, IV iron therapy is associated with a higher risk of certain adverse maternal and neonatal complications in women with iron deficiency anaemia (IDA) in pregnancy and postpartum.

The investigators conducted a repeated cross-sectional analysis of women aged 13–50 years with pregnancy and delivery data at >20 weeks’ gestation available from a large research database from 2011 to 2021. Using the International Classification of Diseases insurance claims codes, 110,719 pregnancies complicated by IDA were identified. Approximately 8,000 of these women with IDA had received IV iron therapy.

Women receiving IV iron therapy were older than those who were not (median age 31 vs 30 years; p<0.001), but gestational age at delivery was similar between groups (median age 37.5 vs 37.67 years; p=0.113). [SMFM 2026, abstract 302]

Looking at pregnancy complications at baseline, participants who were receiving IV iron therapy in pregnancy or through 6 weeks postpartum had a lower incidence of foetal growth restriction (5.13 percent vs 7.7 percent; p<0.001) than those who were not, but more women on IV iron underwent assisted reproductive technology (4.07 percent vs 2.7 percent; p<0.001).

Regarding maternal comorbidity index (MCI), those on IV iron had fewer incidences of placenta previa (3.2 percent vs 4.4 percent), previous Caesarean section (10.8 percent vs 12.13 percent), and diabetes (pre-existing: 4.27 percent vs 5.7 percent; gestational: 13.51 percent vs 15.15 percent; p<0.001 for all) than those who were not.

Conversely, participants who had IV iron therapy had higher incidences of asthma (8.24 percent vs 6.51 percent), chronic hypertension (9.68 percent vs 8.35 percent), and pre-existing cardiac disease (6.09 percent vs 4.2 percent) compared with those who had not (p<0.001 for all).

Maternal, neonatal outcomes by IV iron therapy

After adjusting for age, rurality, and MCI, IV iron therapy was associated with higher odds of postpartum depression (5.55 percent vs 3.77 percent; adjusted odds ratio [aOR], 1.50, 95 percent confidence interval [CI], 1.36–1.66), postpartum haemorrhage (4.68 percent vs 3.74 percent; aOR, 1.25, 95 percent CI, 1.12–1.40), and severe maternal morbidity (5.47 percent vs 4.8 percent; aOR, 1.14, 95 percent CI, 1.03–1.26).

Using Cox proportional hazards model, IV iron therapy was also associated with a markedly increased risk of neonatal IDA (58.97 percent vs 41.1 percent; aOR, 1.78, 95 percent CI, 1.73–1.83).

IV iron therapy did not appear to influence the incidences of maternal blood transfusion (2.26 percent vs 2.04 percent; aOR, 1.12) and admission to the neonatal intensive care unit (0.08 percent vs 0.1 percent; aOR, 0.71).

Contrasting evidence

Anaemia during pregnancy is a common occurrence among women in developing nations; it affects over two-thirds of expectant mothers, with 95 percent of cases being caused by iron deficiency. Iron supplementation during pregnancy has become a common practice for preventing IDA. [Cureus 2022;14:e28918]

The use of IV iron in women of reproductive age has rapidly increased as newer preparations with shorter administration times have become available. [Med J Aust 2020;213:85-86] However, evidence regarding its safety shows conflicting evidence. [Eur J Haematol 2024;113:842-851; Blood 2025;146: 2703]

“[The current] findings may reflect residual confounding with more severe anaemia in those receiving IV iron therapy, which could not be evaluated or controlled for in this dataset,” noted Dr Monica Sosa from the University of Utah Health, Salt Lake City, Utah, US, and colleagues. The researchers called for further investigation to improve the management of maternal IDA.