Introduction to workshop on iron screening and supplementation in iron-replete pregnant women and young children

Iron Homeostasis During Pregnancy: Maternal, Placental, and Fetal Regulatory Mechanisms

Pregnancy entails a large negative balance of iron, an essential micronutrient. During pregnancy, iron requirements increase substantially to support both maternal red blood cell expansion and the development of the placenta and fetus. As insufficient iron has long been linked to adverse pregnancy outcomes, universal iron supplementation is common practice before and during pregnancy. However, in high-resource countries with iron fortification of staple foods and increased red meat consumption, the effects of too much iron supplementation during pregnancy have become a concern because iron excess has also been linked to adverse pregnancy outcomes. In this review, we address physiologic iron homeostasis of the mother, placenta, and fetus and discuss perturbations in iron homeostasis that result in pathological pregnancy. As many mechanistic regulatory systems have been deduced from animal models, we also discuss the principles learned from these models and how these may apply to human pregnancy.

Correlation between high serum ferritin levels and adverse pregnancy outcomes in women with gestational diabetes mellitus

Aims

To explore the association between higher serum ferritin (SF) levels in mid-pregnancy and adverse pregnancy outcomes in gestational diabetes mellitus (GDM) pregnancies, then develop a predictive cut-off value that might effectively predict the risk of adverse pregnancy outcomes in future clinical.

Methods

The study involved 201 pregnant women with GDM. 201 gestational age and parity matched normoglycemic pregnant women were taken as control group. The differences in clinical data were compared by the Mann-Whitney U test and Chi-square tests. Multivariate logistic regression was used to determine the relationship between SF and GDM-relate adverse pregnancy outcomes. The predicted value of SF level was determined through receiver operating characteristic (ROC) curve analysis.

Results

SF level was significantly higher in women with GDM [16.10 (27.30-9.50) (ng/mL) vs. 12.04 (18.11-7.06) (ng/mL), (p < 0.001)]. Meanwhile, higher levels of SF were also discovered in GDM women with preeclampsia and neonatal hypoglycemia and respiratory distress (all p < 0.05). In the adjusted model, a positive association was shown between SF and preeclampsia [adjusted odds ratio (AOR) = 1.032, 95%CI = 1.004-1.060, p = 0.024], neonatal hypoglycemia [adjusted odds ratio (AOR) = 1.047, 95%CI = 1.022-1.072, p < 0.001] and respiratory distress outcomes (AOR = 1.034, 95%CI = 1.011-1.058, p = 0.004) respectively. The area under ROC curve (AUC) for prediction of preeclampsia by SF combined with serum calcium, age, pre-pregnancy BMI and gestational weight gain (GWG) was 0.658 (95% CI = 50.8-80.8%, p = 0.028) with the cut-off value of 24.45 ng/mL, and the sensitivity and specificity were 58.8.0% and 64.3%, respectively. To predict neonatal hypoglycemia, the clinical point value of SF was 27.43 ng/mL with AUC was 0.800, sensitivity and specificity was 90.5% and 68.0% respectively. Predicting neonatal respiratory distress, the AUC value of the SF level was 0.730, with a cut-off value of 27.37 ng/mL and the sensitivity and specificity were 52.0% and 86.5%, respectively.

Conclusions

Higher level of SF in mid-pregnancy was significantly associated with the risk of GDM and GDM-relate adverse pregnancy outcomes. Moreover, SF levels have moderate clinical value in predicting the adverse outcomes of maternal preeclampsia, neonatal hypoglycemia and respiratory distress.

Impact of iron supplementation on gestational diabetes mellitus: A literature review

Gestational diabetes mellitus (GDM) is a common complication of pregnancy, affecting 14% of pregnancies worldwide, and the prevention of pathological hyperglycaemia during pregnancy is meaningful for global public health. The role of iron supplementation in the progression of GDM has been of significant interest in recent years. Iron is a micronutrient that is vital during pregnancy; however, given the toxic properties of excess iron, it is probable that prophylactic iron supplementation will increase the risk of adverse pregnancy outcomes, including GDM. It is critical to clarify the effect of iron supplementation on the risk of GDM. Therefore, in this review, we comprehensively assess the role of iron in pregnancy. This review aimed to analyse the necessity of iron supplementation and maintenance of iron homeostasis during pregnancy, particularly reviewing the role and function of iron in beta cells and examining the mechanisms of excess iron contributing to the pathogenesis of GDM. Moreover, we aimed to discuss the association of haemoglobin and ferritin with GDM and identify priority areas for research.

Testing equivalence of two doses of intravenous iron to treat iron deficiency in pregnancy: A randomised controlled trial

OBJECTIVE

To test equivalence of two doses of intravenous iron (ferric carboxymaltose) in pregnancy.

DESIGN

Parallel, two-arm equivalence randomised controlled trial with an equivalence margin of 5%.

SETTING

Single centre in Australia.

POPULATION

278 pregnant women with iron deficiency.

METHODS

Participants received either 500 mg (n=152) or 1000mg (n=126) of intravenous ferric carboxymaltose in the second or third trimester.

MAIN OUTCOME MEASURES

The proportion of participants requiring additional intravenous iron (500mg) to achieve and maintain ferritin >30ug/L (diagnostic threshold for iron deficiency) at 4 weeks post-infusion, and at 6 weeks, and 3-, 6- and 12-months postpartum. Secondary endpoints included repeat infusion rate, iron status, birth, and safety outcomes.

RESULTS

The two doses were not equivalent within a 5% margin at any timepoint. At 4 weeks post infusion, 26/73 (36%) participants required a repeat infusion in the 500 mg group compared with 5/67 (8%) in the 1000 mg group (difference in proportions, 0.283 95% confidence interval (0.177, 0.389)). Overall, participants in the 500 mg arm received twice the repeat infusion rate (0.81 (SD= 0.824 vs 0.40 (SD= 0.69), rate ratio 2.05, 95% CI (1.45, 2.91)).

CONCLUSIONS

Administration of 1000 mg ferric carboxymaltose in pregnancy maintains iron stores and reduces the need for repeat infusions. A 500 mg dose requires ongoing monitoring to ensure adequate iron stores are reached and sustained.

Multiple Indicators of Undernutrition, Infection, and Inflammation in Lactating Women Are Associated with Maternal Iron Status and Infant Anthropometry in Panama: The MINDI Cohort

Maternal infections, nutrient deficiencies, and inflammation (MINDI) co-exist in lactating indigenous women in Panama, but their impact on maternal iron status and infant growth is unknown. For this secondary analysis of cross-sectional data of lactating mothers from our MINDI cohort, we investigated associations of MINDI variables with maternal anemia, elevated serum transferrin receptor (sTfR), low serum iron, hepcidin, ferritin, and infant weight-for-age (WAZ), length-for-age (LAZ), and head-circumference-for-age (HCAZ) Z-scores in 99 mother-infant dyads. A bootstrapping resampling procedure preselected covariates for inclusion in multivariable regressions models from chronic maternal infections and nutritional status [folate, vitamins A, D, retinol-binding protein (RBP), insulin-growth factor-1 (IGF-1)] and inflammation [C-reactive protein (CRP), cytokines, platelet indices] indicators. Anemia was prevalent (53.5%) but underestimated due to widespread low plasma volume (<2.2 L, 79.9%) and was associated with indicators of malnutrition [lower IGF-1, body mass index (BMI), vitamin D, and intake of green/leafy vegetables], but not inflammation. Higher CRP was associated with lower serum iron, and higher hepcidin and ferritin, whereas maternal platelets were associated with lower HCAZ (β = −0.22), WAZ (β = −0.17), and LAZ (β = −0.17). Higher LAZ was also associated with maternal serum vitamin D (β = 0.23), whereas maternal iron supplementation lowered LAZ (β = −0.22). Assessment of iron status in this MINDI cohort is complex and supplementation strategies must consider consequences for both the mother and the infant.

Heavy metal ion concentration in the amniotic fluid of preterm and term pregnancies from two cities with different industrial output

The growth and development of the fetus is a complex phenomenon that can be influenced by several variables. High quantities of heavy metal ions in the amniotic fluid have been linked to poor health, especially in industrial, polluted and poor areas. The aim of the present study was to assess the differences in the concentration of these ions between preterm (weeks 15-37) and term pregnancies (starting at week 37). Another objective was to compare pregnancies from two cities with different industry levels. Two sample lots from two Romanian cities were analyzed. A total of 100 patients from Timisoara were compared with 60 from Petrosani, a heavy industry city in Romania. Demographic data were collected, and amniocentesis was performed on all women. Lead (Pb), copper (Cu), nickel (Ni), cadmium (Cd), arsenic (As), iron (Fe) and zinc (Zn) concentrations were assessed. Descriptive and analytical statistics were performed using the Mann-Whitney U test for non-parametric data and the Fisher's exact test for categorical data. In addition, categorical data was represented graphically. In the Timisoara cohort, the differences in heavy metal concentrations between preterm and term pregnancies were not statistically significant. In the Petrosani cohort, however, the concentrations of Zn (P=0.02606) and Cd (P=0.01512) were higher in preterm than in term pregnancies. When comparing the two cohorts as a whole, the concentration of Pb (P=0.04513), Cd (P=0.00002), As (P=0.03027) and Zn (P<0.00001) were higher in the patients from Petrosani than in those from Timisoara. Only Cu concentrations were higher in the Timisoara cohort (P<0.00001). The concentrations of Ni (P=0.78150) and Fe (P=0.44540) did not differ statistically. Thus, amniocentesis is an important diagnostic and exploratory tool in determining differences in the concentrations of elements such as heavy metal ions. Research over a longer period of time should be carried out to examine the relation between heavy metal ions concentration and possible postnatal health outcomes.

Effects of maternal iron status on placental and fetal iron homeostasis

Iron deficiency is common worldwide and is associated with adverse pregnancy outcomes. The increasing prevalence of indiscriminate iron supplementation during pregnancy also raises concerns about the potential adverse effects of iron excess. We examined how maternal iron status affects the delivery of iron to the placenta and fetus. Using mouse models, we documented maternal homeostatic mechanisms that protect the placenta and fetus from maternal iron excess. We determined that under physiological conditions or in iron deficiency, fetal and placental hepcidin did not regulate fetal iron endowment. With maternal iron deficiency, critical transporters mediating placental iron uptake (transferrin receptor 1 [TFR1]) and export (ferroportin [FPN]) were strongly regulated. In mice, not only was TFR1 increased, but FPN was surprisingly decreased to preserve placental iron in the face of fetal iron deficiency. In human placentas from pregnancies with mild iron deficiency, TFR1 was increased, but there was no change in FPN. However, induction of more severe iron deficiency in human trophoblast in vitro resulted in the regulation of both TFR1 and FPN, similar to what was observed in the mouse model. This placental adaptation that prioritizes placental iron is mediated by iron regulatory protein 1 (IRP1) and is important for the maintenance of mitochondrial respiration, thus ultimately protecting the fetus from the potentially dire consequences of generalized placental dysfunction.

Physiologic requirement for iron in pregnant women, assessed using the stable isotope tracer technique

BACKGROUND

Knowledge of the physiologic requirement for iron, the core index for the formulation of a dietary reference intake (DRI), is of great importance for the health of a pregnant woman and her fetus, and can help a mother accurately plan her iron supplementation. However, direct measurements of the physiologic requirement for iron during pregnancy are still lacking.

METHOD

Eleven women of reproductive age from Hebei Province, China, who planned to become pregnant in the near future, were enrolled between January and March 2015 and included in the final analysis. Subjects participated in a 2-week metabolic trial in which they consumed 50 mg of the stable isotope 58Fe, and were then followed for ~ 2 years. The abundance of 58Fe and the total iron concentration in the circulation were measured using Multi-collector Inductively-Coupled Plasma Mass Spectrometry and Atomic Absorption Spectroscopy, respectively. The physiologic requirement for iron during pregnancy was then calculated by the formula derived from our previously published work.

RESULTS

The mean physiologic requirement for iron in the 11 subjects, across their entire pregnancies, was 3.05 mg.d- 1 in total and 44.0 μg.kg- 1.d- 1 after adjustment for body mass. The physiologic requirements for iron in the first, second, and third trimesters were 2.04 mg.d- 1, 3.26 mg.d- 1, and 4.13 mg.d- 1, respectively. When adjusted for body mass, the physiologic requirements for iron in different trimesters were 32.3 μg.kg- 1.d- 1, 46.9 μg.kg- 1.d- 1, and 55.7 μg.kg- 1.d- 1, respectively.

CONCLUSION

We preliminarily explored the physiologic requirement for iron in pregnant women. The data demonstrated that pregnant women needed about twice iron than non-pregnant women. This research may be helpful for the design of future studies and the modification of iron DRIs.

TRIAL REGISTRATION

ChiCTR, ChiCTR-OCH-14004302. Registered 14 February 2014, http://www.chictr.org.cn/showproj.aspx?proj=5267.

The Benefits and Risks of Iron Supplementation in Pregnancy and Childhood

Iron deficiency is the most common micronutrient deficiency in the world and disproportionately affects pregnant women and young children. Iron deficiency has negative effects on pregnancy outcomes in women and on immune function and neurodevelopment in children. Iron supplementation programs have been successful in reducing this health burden. However, iron supplementation of iron-sufficient individuals is likely not necessary and may carry health risks for iron-sufficient and potentially some iron-deficient populations. This review considers the physiology of iron as a nutrient and how this physiology informs decision-making about weighing the benefits and risks of iron supplementation in iron-deficient, iron-sufficient, and iron-overloaded pregnant women and children.

Maximising benefits and minimising adverse effects of micronutrient interventions in low- and middle-income countries

Micronutrient deficiencies are widespread and disproportionately affect women and children in low- and middle-income countries (LMIC). Among various interventions, food fortification and supplementation with micronutrients have been proven to be cost-effective. The aim of the present paper is to review existing literature to assess risks of excessive intake in LMIC to then highlight programmatic changes required to maximise benefits of micronutrient interventions while minimising risks of adverse effects. While very few LMIC have national food consumption surveys that can inform fortification programmes, many more are implementing mandatory fortification programmes. The risks of inadequate micronutrient intakes were common, but risks of excessive intakes were also present for iodine, vitamin A, folic acid and iron. Excessive salt consumption, high concentrations of iodine in ground-water and excessive levels of iodisation were linked with excessive iodine intake. For vitamin A, overlapping interventions were the main risk for excessive intake; whereas for iron, contamination with iron from soil and screw-wares of millers and high iron concentration in drinking-water increased the risk of excessive intake, which could be further exacerbated with fortification. Before implementing micronutrient interventions, adherence to the basic principles of documenting evidence confirming that the deficiency in question exists and that fortification will correct this deficiency is needed. This can be supported with dietary intake assessments and biochemical screening that help diagnose nutrient deficiencies. Targeting micronutrient interventions, although programmatically challenging, should be considered whenever possible. Moreover, closer monitoring of appropriate fortification of foods and overlapping interventions is needed.

Placental iron transport: The mechanism and regulatory circuits

As the interface between the fetal and maternal circulation, the placenta facilitates both nutrient and waste exchange for the developing fetus. Iron is essential for healthy pregnancy, and transport of iron across the placenta is required for fetal growth and development. Perturbation of this transfer can lead to adverse pregnancy outcomes. Despite its importance, our understanding of how a large amount of iron is transported across placental membranes, how this process is regulated, and which iron transporter proteins function in different placental cells remains rudimentary. Mechanistic studies in mouse models, including placenta-specific deletion or overexpression of iron-related proteins will be essential to make progress. This review summarizes our current understanding about iron transport across the syncytiotrophoblast under physiological conditions and identifies areas for further investigation.

Iron Supplementation during Pregnancy and Infancy: Uncertainties and Implications for Research and Policy

Iron is particularly important in pregnancy and infancy to meet the high demands for hematopoiesis, growth and development. Much attention has been given to conditions of iron deficiency (ID) and iron deficient anemia (IDA) because of the high global prevalence estimated in these vulnerable life stages. Emerging and preliminary evidence demonstrates, however, a U-shaped risk at both low and high iron status for birth and infant adverse health outcomes including growth, preterm birth, gestational diabetes, gastrointestinal health, and neurodegenerative diseases during aging. Such evidence raises questions about the effects of high iron intakes through supplementation or food fortification during pregnancy and infancy in iron-replete individuals. This review examines the emerging as well as the current understanding of iron needs and homeostasis during pregnancy and infancy, uncertainties in ascertaining iron status in these populations, and issues surrounding U-shaped risk curves in iron-replete pregnant women and infants. Implications for research and policy are discussed relative to screening and supplementation in these vulnerable populations, especially in developed countries in which the majority of these populations are likely iron-replete.

Integrating themes, evidence gaps, and research needs identified by workshop on iron screening and supplementation in iron-replete pregnant women and young children

This report addresses the evidence and the uncertainties, knowledge gaps, and research needs identified by participants at the NIH workshop related to iron screening and routine iron supplementation of largely iron-replete pregnant women and young children (6-24 mo) in developed countries. The workshop presentations and panel discussions focused on current understanding and knowledge gaps related to iron homeostasis, measurement of and evidence for iron status, and emerging concerns about supplementing iron-replete members of these vulnerable populations. Four integrating themes emerged across workshop presentations and discussion and centered on 1) physiologic or developmental adaptations of iron homeostasis to pregnancy and early infancy, respectively, and their implications, 2) improvement of the assessment of iron status across the full continuum from iron deficiency anemia to iron deficiency to iron replete to iron excess, 3) the linkage of iron status with health outcomes beyond hematologic outcomes, and 4) the balance of benefit and harm of iron supplementation of iron-replete pregnant women and young children. Research that addresses these themes in the context of the full continuum of iron status is needed to inform approaches to the balancing of benefits and harms of screening and routine supplementation.

Emerging understanding and measurement of plasma volume expansion in pregnancy

Plasma volume expansion is an important component of a successful pregnancy. The failure of maternal plasma volume expansion has been implicated in adverse obstetric outcomes such as pre-eclampsia, fetal growth restriction, and preterm birth. Altered iron homeostasis and elevated maternal hemoglobin concentrations have also been associated with adverse pregnancy outcomes; limited data have suggested that these effects may be mediated by inadequate plasma volume expansion. In addition, it has been noted that pregnant, obese women, compared with lean subjects, have decreased plasma volume expansion along with impaired iron homeostasis and increased inflammation. Current estimates of plasma volume expansion are outdated and do not necessarily reflect contemporary obstetric populations. Moreover, the validation of clinically applicable methods of plasma volume determination as well as enhanced methodologies should be a priority. Further study is needed to characterize diminished plasma volume expansion during pregnancy and to understand the potential role of impaired iron homeostasis and inflammation in adverse obstetric outcomes, especially in obese women.