1. Acute Iron Overdose in the Setting of Active Labor with Fetal Umbilical Cord Serum Iron Concentration
William Eggleston, Pharm.D.1 and Christine M. Stork, Pharm.D., DABAT1,2
1Upstate Medical University, Upstate NY Poison Center, Syracuse, NY, 2Upstate Medical University, Department of Emergency Medicine, Syracuse, NY,
DISCUSSION
Iron supplementation is common during pregnancy, but overdose is uncommon during the third trimester
There is limited literature describing iron toxicity in pregnant females
Fetal toxicity after iron overdose is not well understood
Available literature suggests worse fetal outcomes with higher serum iron concentrations
Mechanism of toxicity is unclear
Possibly due to fetal iron toxicity or maternal hypotension and acidosis
There is limited human literature discussing iron’s ability to cross the placenta
Two human case reports with umbilical cord serum iron concentrations were within the normal range
Single case report of fetal autopsy after maternal iron overdose revealed negative iron staining of organs and placenta
Iron administration to pregnant ewes did not result in detectable fetal serum iron concentrations
Teratogenetic effects of deferoxamine are unclear
Animal studies suggest skeletal malformations, but results are conflicting
Spontaneous abortions reported with chronic use
Benefits likely outweigh the risk in the setting of acute iron overdose meeting criteria for chelation
INTRODUCTION
Numerous OTC and prescription preparations contain iron
Available in numerous salt forms with varying elemental iron concentration (Figure 2)
Commonly supplemented during pregnancy
Toxic effects in overdose are well described
Largely gastrointestinal irritant with subsequent hypotension, altered mental status, and lactic acidosis
Risk of fetal toxicity is unknown after overdose
Case
Fetal Outcome
-30 yo female at 36 weeks gestation1
-Fetus delivered 31 hours post-ingestion
-Umbilical cord serum iron: 14 micro-mol/L (79.8 mg/dL)
-Deferoxamine administered
-Survived without complication
-17 yo pregnant female2
-Patient expired on hospital day 3
-Iron stains performed on fetal organs and placenta during autopsy were negative
24 yo female at 34 weeks gestation3
Spontaneous labor 8 hours post-ingestion
Successful delivery 14 hours post-ingestion
Umbilical cord serum iron: 115 mcg/dL (normal, mcg/dL)
-Iron staining of the placenta did not demonstrate significant deposition
CASE
A 28 year-old 32-week pregnant female presented to the Emergency Department with vomiting, lethargy, and respiratory depression after a reported ingestion of an unknown amount of an unidentified iron supplement within the previous 10 hours. Vital signs included: blood pressure, 107/75 mmHg; heart rate, 63 beats per minute; temperature, 36.4⁰ Celsius. Significant physical examination findings included: mental status depression, pallor, and repeated vomiting. Laboratory assessment was notable for: iron, 470 mcg/dL; potassium, 3.3 mEq/L; lactate, 1.9 mmol/L; pH, 7.4; pCO2, 28.7; HCO3, 22 mEq/L. An abdominal radiograph was negative for tablets. The fetal heart rate was strong and regular. Multiple boluses of 0.9% saline were infused without hemodynamic improvement. Mental status worsened and active labor began (2 to 5 cm dilation over 1 hour) after which hypotension (90/50 mmHg) prompted deferoxamine administration. She tolerated deferoxamine without complication and hemodynamics improved over the next 3 hours. Repeat lactate was 1.4 mmol/L 6 hours after presentation, although the patient remained altered.
The neonate was delivered 8 hours after presentation without complication. Venous umbilical cord blood showed an iron concentration of 67 mcg/dL (normal ≈ 100 mcg/dL). The neonate had a transient acidosis with a pH, 7.17; pCO2, 49; pO2, 62; which resolved with airway management.
Approximately 24 hours after presentation, the patient’s mental status improved, laboratory derangements resolved, and deferoxamine was stopped. She was discharged home without sequelae.
Figure 1: Review of the human literature pertaining to iron’s ability to cross the placenta in overdose.
Iron Source
Elemental Iron (%)
Ferrous chloride 28
Ferrous fumarate 33
Ferrous gluconate 12
Ferrous lactate 19
Ferrous sulfate 20
Carbonyl iron* 98
Polysaccharide iron* 46
CONCLUSION
Iron overdose during pregnancy is rare, and fetal toxicity is poorly understood
Limited data suggests higher serum concentrations are linked to worse fetal outcomes
Available literature, along with this case report, suggest that iron does not readily cross the placenta in overdose
Figure 2: Elemental iron concentrations (%) of selected iron preparations.
*Despite their high iron content, non-ionic iron sources have limited gastrointestinal absorption resulting in reduced toxicity
Citations
Olenmark M et al. Fatal iron intoxication in late pregnancy. J Toxicol Clin Toxicol. 1987; 25(4):
Strom RL et al. Fatal iron poisoning in a pregnant female. Minn Med. 1976; 59(7):483-9.
Rayburn WF et al. Iron overdose during pregnancy: successful therapy with deferoxamine. Am J Obstet Gynecol. 1983; 147(6):717-8.