(519) Maternal and Fetal Adverse Reactions with Iron Infusions

As oral iron is poorly tolerated and inefficient, intravenous (IV) iron has become an increasingly common strategy to manage iron deficiency in pregnancy. While generally considered safe, emerging reports have resulted in FDA warnings regarding fetal bradycardia. We sought to characterize the maternal and fetal effects of adverse reactions observed during IV iron infusions at our institution.

Study Design:

We reviewed all adverse drug reaction events in pregnancy during IV iron infusions from 2018-2024 using the institutional event reporting system. Data was extracted from electronic medical records and external fetal monitoring (EFM) tracings if performed; institutional policy utilizes continuous EFM during infusions in viable pregnancies. We evaluated the incidence of maternal reactions and compared characteristics between patients who did/did not experience EFM changes.


Results:

Of 2,994 infusions in pregnancy during the study period, 41 (1.4%) adverse maternal reactions occurred. Most occured with iron dextran (93%). The most common maternal symptoms were shortness of breath (59%) and chest pain/tightness (37%); the majority of patients had no prior history of drug or food allergies (61%). EFM decelerations were documented in 19 cases (46%). Between those with and without decelerations, there were no differences in age, race, gestational age, or prior allergies; there were also no differences in iron formulation, pre-medication or test dose (Table). Most decelerations occurred within 5 minutes of infusion (68%) and all occurred 1-2 minutes after start of maternal symptoms. The median time required for resolution back to fetal baseline was 5 minutes (range: 1 to >10 minutes); 2 patients experienced prolonged fetal bradycardia unresponsive to resuscitation and delivered via emergent cesarean.

Conclusion:

Maternal adverse events during IV iron transfusion may be associated with concerning EFM changes, regardless of iron formulation and premedication. Further large studies should assess whether continuous EFM during iron infusion is needed.