(484) Swiss Solutions to Pregnant Problems: Evaluating the Ganzoni Formula in Anemic Individuals Receiving IV Iron

Objective:
Iron deficiency anemia (IDA) during pregnancy affects 14-56% of pregnant women globally. In the U.S., IDA affects from 6.9% (1^st trimester) - 28.4% (3^rd trimester) of pregnancies. Maternal mortality / feto-maternal morbidity are directly (20%) and indirectly (50%) attributed to IDA. Since 1970, the Ganzoni formula (GF) has been widely used to calculate total iron deficit in other medical specialties but has not yet been applied in pregnancy. We aimed to assess the utility of the GF in pregnant patients with IDA receiving IV iron.

Study Design:
We conducted a retrospective review of pregnant patients who delivered at our level IV center from 7/2020 – 7/2025 and received IV iron for IDA. GF was calculated as: body weight (kg) x [target hemoglobin (Hb) – actual Hb (g/dL)] x 2.4 + 500mg (iron stores), with a 2.4 factor derived from assumptions of blood volume (7% of body weight) and Hb iron content of 0.34%. Weight at initial iron transfusion was used. Pre- and post-transfusion Hbs were compared to determine treatment efficacy, with a target Hb of 11g/dL at delivery. Exclusion criteria included hemoglobinopathies. ROC analysis identified an initial GF threshold at which primary outcome was achieved.

Results:
Of 857 pregnant individuals who received IV iron, 250 delivered >=6 weeks after initial transfusion (29.2%). Mean index Hb was 8.68g/dL [range 6.3-12.5] with mean delivery Hb of 11.07g/dL [range 6.2-14.0]. Patients received an average of 781.3mg [range 200-1600] of IV iron across 1-5 separate, inpatient / outpatient infusions. GF deficits ranged from 372.8-2259.7mg. ROC analysis identified 1117.28mg as predictive threshold to achieve target Hb of >=11g/dL (p = 0.0002), regardless of dose frequency.

Conclusion:
GF, though previously untested in pregnancy, can be utilized to evaluate iron deficits in patients with known IDA. Patients with a GF deficit of < 1117mg were less likely to achieve a target Hb of 11g/dL regardless of treatment dosage and frequency. Our findings support the utility of GF in a pregnant population, though further validation is needed.