Cord blood transferrin receptors to assess fetal iron status

Preterm Piglets Born by Cesarean Section as a Suitable Animal Model for the Study of Iron Metabolism in Premature Infants

Preterm infants are most at risk of iron deficiency. However, our knowledge of the regulation of iron homeostasis in preterm infants is poor. The main goal of our research was to develop and validate an animal model of human prematurity to assess iron status in preterm infants. We performed a cesarean section on sows on the 109th day of pregnancy, which corresponds to the last trimester of human pregnancy. Preterm piglets showed decreased body weight, red blood cell indices, plasma iron level and transferrin saturation. Interestingly, higher hepatic and splenic non-heme iron content and plasma and hepatic ferritin levels were found in premature piglets compared with term ones. In addition, premature piglets showed higher mRNA levels of iron-regulatory hormone hepcidin in the liver than term animals, which have not been reflected in higher plasma hepcidin-25 levels. We also showed changes in hepcidin regulators, including hepatic bone morphogenetic protein 6, plasma erythroferrone and growth differentiation factor 15 in preterm piglets. Consequently, no difference was observed in iron-exporter ferroportin levels in the spleen and liver. Overall, it seems that premature piglets show a pattern of iron metabolism characteristic of functional iron deficiency and iron accumulation in the tissue.

Biomarkers of Brain Dysfunction in Perinatal Iron Deficiency

Iron deficiency in the fetal and neonatal period (perinatal iron deficiency) bodes poorly for neurodevelopment. Given its common occurrence and the negative impact on brain development, a screening and treatment strategy that is focused on optimizing brain development in perinatal iron deficiency is necessary. Pediatric societies currently recommend a universal iron supplementation strategy for full-term and preterm infants that does not consider individual variation in body iron status and thus could lead to undertreatment or overtreatment. Moreover, the focus is on hematological normalcy and not optimal brain development. Several serum iron indices and hematological parameters in the perinatal period are associated with a risk of abnormal neurodevelopment, suggesting their potential use as biomarkers for screening and monitoring treatment in infants at risk for perinatal iron deficiency. A biomarker-based screening and treatment strategy that is focused on optimizing brain development will likely improve outcomes in perinatal iron deficiency.

Iron stores at birth in a full-term normal birth weight birth cohort with a low level of inflammation

Iron stores at birth are essential to meet iron needs during the first 4-6 months of life. The present study aimed to investigate iron stores in normal birth weight, healthy, term neonates. Umbilical cord blood samples were collected from apparently normal singleton vaginal deliveries (n=854). Subjects were screened and excluded if C-reactive protein (CRP) > 5 mg/l or α1-acid glycoprotein (AGP) > 1 g/l, preterm (<37 complete weeks), term < 2500g or term > 4000g. In total, 762 samples were included in the study. Serum ferritin, soluble transferrin receptor (sTfR), hepcidin, and erythropoietin (EPO) were measured in umbilical cord blood samples; total body iron (TBI) (mg/kg) was calculated using sTfR and ferritin concentrations. A total of 19.8% newborns were iron deficient (ferritin 35 μg/l) and an additional 46.6% had insufficient iron stores (ferritin < 76 μg/l). There was a positive association between serum ferritin and sTfR, hepcidin, and EPO. Gestational age was positively associated with ferritin, sTfR, EPO, and hepcidin. In conclusion, we demonstrate a high prevalence of insufficient iron stores in a Chinese birth cohort. The value of cord sTfR and TBI in the assessment of iron status in the newborn is questionable, and reference ranges need to be established.

Hepcidin, Serum Iron, and Transferrin Saturation in Full-Term and Premature Infants during the First Month of Life: A State-of-the-Art Review of Existing Evidence in Humans

Neonates regulate iron at birth and in early postnatal life. We reviewed literature from PubMed and Ovid Medline containing data on umbilical cord and venous blood concentrations of hepcidin and iron, and transferrin saturation (TSAT), in human neonates from 0 to 1 mo of age. Data from 59 studies were used to create reference ranges for hepcidin, iron, and TSAT for full-term-birth (FTB) neonates over the first month of life. In FTB neonates, venous hepcidin increases 100% over the first month of life (to reach 61.1 ng/mL; 95% CI: 20.1, 102.0 ng/mL) compared with umbilical cord blood (29.7 ng/mL; 95% CI: 21.1, 38.3 ng/mL). Cord blood has a high concentration of serum iron (28.4 μmol/L; 95% CI: 26.0, 31.1 μmol/L) and levels of TSAT (51.7%; 95% CI: 46.5%, 56.9%). After a short-lived immediate postnatal hypoferremia, iron and TSAT rebounded to approximately half the levels in the cord by the end of the first month. There were insufficient data to formulate reference ranges for preterm neonates.

Iron Homeostasis Disruption and Oxidative Stress in Preterm Newborns

Iron is an essential micronutrient for early development, being involved in several cellular processes and playing a significant role in neurodevelopment. Prematurity may impact on iron homeostasis in different ways. On the one hand, more than half of preterm infants develop iron deficiency (ID)/ID anemia (IDA), due to the shorter duration of pregnancy, early postnatal growth, insufficient erythropoiesis, and phlebotomy losses. On the other hand, the sickest patients are exposed to erythrocytes transfusions, increasing the risk of iron overload under conditions of impaired antioxidant capacity. Prevention of iron shortage through placental transfusion, blood-sparing practices for laboratory assessments, and iron supplementation is the first frontier in the management of anemia in preterm infants. The American Academy of Pediatrics recommends the administration of 2 mg/kg/day of oral elemental iron to human milk-fed preterm infants from one month of age to prevent ID. To date, there is no consensus on the type of iron preparations, dosages, or starting time of administration to meet optimal cost-efficacy and safety measures. We will identify the main determinants of iron homeostasis in premature infants, elaborate on iron-mediated redox unbalance, and highlight areas for further research to tailor the management of iron metabolism.

Iron status in small for gestational age and appropriate for gestational age infants at birth

PURPOSE

This study compared the iron statuses of small for gestational age (SGA) and appropriate for gestational age (AGA) infants at birth.

METHODS

The clinical data of 904 newborn infants admitted to the neonatal intensive care unit were reviewed. Blood samples were drawn from the infants within 24 hours after birth. Serum ferritin level was used as a marker of total iron status.

RESULTS

In this study, 115 SGA (GA, 36.5±2.9 weeks; birth weight [BW], 1,975±594.5 g) and 717 AGA (GA, 35.1±3.5 weeks; BW, 2,420.3±768.7 g) infants were included. The SGA infants had higher hematocrit levels (50.6%±5.8% vs. 47.7%±5.7%, P<0.05) than the AGA infants. No difference in serum ferritin level (ng/mL) was found between the groups (mean [95% confidence interval]: SGA vs. AGA infants, 139.0 [70.0-237.0] vs. 141.0 [82.5-228.5]). After adjusting for gestational age, the SGA infants had lower ferritin levels (147.1 ng/mL [116.3-178.0 ng/mL] vs. 189.4 ng/mL [178.0-200.8 ng/ mL], P<0.05). Total body iron stores were also lower in the SGA infants than in the AGA infants (185.6 [153.4-211.7] vs 202.2 [168.7-241.9], P<0.05).

CONCLUSION

The SGA infants had lower ferritin and total body iron stores than the AGA infants. The SGA infants affected by maternal hypertension who were born at late preterm had an additional risk of inadequate iron store. Iron deficiency should be monitored in these infants during follow-up.

Biomarkers of Nutrition for Development (BOND)-Iron Review

This is the fifth in the series of reviews developed as part of the Biomarkers of Nutrition for Development (BOND) program. The BOND Iron Expert Panel (I-EP) reviewed the extant knowledge regarding iron biology, public health implications, and the relative usefulness of currently available biomarkers of iron status from deficiency to overload. Approaches to assessing intake, including bioavailability, are also covered. The report also covers technical and laboratory considerations for the use of available biomarkers of iron status, and concludes with a description of research priorities along with a brief discussion of new biomarkers with potential for use across the spectrum of activities related to the study of iron in human health.The I-EP concluded that current iron biomarkers are reliable for accurately assessing many aspects of iron nutrition. However, a clear distinction is made between the relative strengths of biomarkers to assess hematological consequences of iron deficiency versus other putative functional outcomes, particularly the relationship between maternal and fetal iron status during pregnancy, birth outcomes, and infant cognitive, motor and emotional development. The I-EP also highlighted the importance of considering the confounding effects of inflammation and infection on the interpretation of iron biomarker results, as well as the impact of life stage. Finally, alternative approaches to the evaluation of the risk for nutritional iron overload at the population level are presented, because the currently designated upper limits for the biomarker generally employed (serum ferritin) may not differentiate between true iron overload and the effects of subclinical inflammation.

The iron status at birth of neonates with risk factors for developing iron deficiency: a pilot study

OBJECTIVE

Small-for-gestational-age (SGA) neonates, infants of diabetic mothers (IDM) and very-low-birth weight premature neonates (VLBW) are reported to have increased risk for developing iron deficiency and possibly associated neurocognitive delays.

STUDY DESIGN

We conducted a pilot study to assess iron status at birth in at-risk neonates by measuring iron parameters in umbilical cord blood from SGA, IDM, VLBW and comparison neonates.

RESULTS

Six of the 50 infants studied had biochemical evidence of iron deficiency at birth. Laboratory findings consistent with iron deficiency were found in one SGA, one IDM, three VLBW, and one comparison infant. None of the infants had evidence of iron deficiency anemia.

CONCLUSIONS

Evidence of biochemical iron deficiency at birth was found in 17% of screened neonates. Studies are needed to determine whether these infants are at risk for developing iron-limited erythropoiesis, iron deficiency anemia or iron-deficient neurocognitive delay.

Gestational Diabetes: Long-Term Central Nervous System Developmental and Cognitive Sequelae

Gestational diabetes is a common complication of pregnancy and occurs in approximately 7% of all pregnancies. It has been associated with an increased rate of congenital anomalies including disturbances of intrauterine growth, delayed brain maturity, and neurobehavioral abnormalities in the offspring. The resulting maternal and fetal metabolic dysfunction leads to diminished iron stores (which can affect red blood cell [RBC] production and subsequent organogenesis), a metabolism-placental perfusion mismatch, increased FFA, increased lactic acidosis, and potential hypoxia. Though most newborns born in the context of gestational diabetes are not significantly affected by it, empirical research suggests gestational diabetes has been associated with lower general intelligence, language impairments, attention weaknesses, impulsivity, and behavioral problems. In extreme cases, it may essentially function as a gestational brain insult. Children who are exposed to poorly controlled gestational diabetes may benefit from some form of tracking or follow-up assessments. Additionally, clinicians evaluating children with developmental learning or cognitive dysfunction may want to seek appropriate gestational diabetes-related information from the parents. A greater understanding of this significant gestational risk may help foster improved prenatal diabetes management and may help reduce the neurodevelopmental effects of gestational diabetes.

The use of cluster and principal component analysis in the estimation of iron status in term newborns

OBJECTIVE

To assess the relationship between parameters of iron homeostasis in infants and clinical features characterizing newborns and their mothers.

METHODS

The goal of the present work was to determine nine iron status parameters, i.e. hepcidin, prohepcidin, soluble transferrin receptor, ferritin, total iron binding capacity, unsaturated iron binding capacity, transferrin saturation, erythropoietin and total iron concentration, in the cord blood of 57 term newborns as well as to determine the complete blood count in their mothers. Moreover, an appraisal of the relationships between all of the iron parameters, the mothers' hematological factors and 12 clinical attributes was carried out using both cluster analysis (CA) and principal component analysis (PCA).

RESULTS

We found that hepcidin is not correlated with its precursor, but it is strongly positively correlated with the total iron concentration. The CA divided all of the 24 parameters into three clusters and showed that certain clinical features, e.g. the APGAR score, mother's age or parity are related to the hepcidin and prohepcidin concentration.

CONCLUSION

We demonstrated that CA and PCA are efficacious methods for assessing the relationship between iron metabolism parameters in cord blood and large amounts of clinical characteristics.

Iron supplementation for preterm infants receiving restrictive red blood cell transfusions: reassessment of practice safety

OBJECTIVE

To reassess iron supplementation practice safety in very low birth weight (VLBW) preterm infants receiving restrictive red blood cell transfusions during initial hospitalization.

STUDY DESIGN

Iron status, including hemoglobin (Hb), serum iron, ferritin, and soluble transferrin receptor (sTfR) levels and reticulocyte count of transfused (n=236) and non-transfused (n=166) preterm infants at ≤24 h and 2, 4 and 8 weeks were recorded. As per protocol, a restrictive blood transfusion policy and supplementation of 5 mg kg(-1) per day of iron polymaltose complex from 4 weeks and 25 mg(-1) per day of vitamin E from 2 weeks were imposed for all infants. Normative reference cord-blood ferritin value of preterm infants was used for comparison. Vitamin E levels and incidence of morbidities associated with prematurity were recorded.

RESULT

At ≤24 h, the characteristics and iron status of both groups were similar. At 2, 4 and 8 weeks, the transfused group had significantly higher Hb, iron and ferritin levels; sTfR levels were lower at 4 and 8 weeks (all indices, P<0.05). At 8 weeks, the median ferritin levels of our transfused group were lower than that of normative reference cord-blood value (115 (50th percentile) vs 79 (43 to 107) μg l(-1), respectively). Vitamin E levels and the incidence of morbidities associated with prematurity of the transfused and non-transfused groups were not different (both indices, P>0.18).

CONCLUSION

Adding iron supplementation to preterm infants receiving restrictive blood transfusions has shown to be a judicious and safe practice in terms of iron status for VLBW preterm infants.

Nutrient deficiencies in the premature infant

Premature infants are a population prone to nutrient deficiencies. Because the early diet of these infants is entirely amenable to intervention, understanding the pathophysiology behind these deficiencies is important for both the neonatologists who care for them acutely and for pediatricians who are responsible for their care through childhood. This article reviews the normal accretion of nutrients in the fetus, discusses specific nutrient deficiencies that are exacerbated in the postnatal period, and identifies key areas for future research.

Influence of maternal diabetes mellitus on fetal iron status

OBJECTIVE

To determine the effects of maternal diabetes on fetal iron status using serum transferrin receptors (STfR) and their ratio to ferritin (TfR-F index) in cord blood.

METHODS

Iron, ferritin, erythropoietin, STfR and haemoglobin concentration were measured and TfR-F index calculated in 97 maternal/cord blood pairs. Forty-nine women had type 1 diabetes (diagnosed before pregnancy) and these were compared with forty-eight non- diabetic controls. The women with type 1 diabetes were recruited consecutively from attendance at the joint antenatal endocrine clinic while the control group of women was recruited from consecutive attendance at the remaining antenatal clinics.

RESULTS

The infants of the diabetic women had significantly lower levels of ferritin (47 vs 169 mug/l; p<0.01) and higher STfR (17.4 vs 12.9 mg/l; p<0.01) and TfR-F index (10.4 vs 5.8; p<0.01) than controls. They were also significantly more acidotic at birth (7.25 vs 7.30; p<0.01), were born at an earlier gestation (36.7 vs 39.7 weeks; p<0.01) and had higher z Scores for weight (0.53 vs 0.02; p = 0.016).

CONCLUSIONS

Maternal diabetes causes depletion of fetal iron stores and is associated with higher fetal iron demands as indicated by higher STfR level and TfR-F index in cord blood.

Predictors of serum ferritin and serum soluble transferrin receptor in newborns and their associations with iron status during the first 2 y of life

BACKGROUND

Adequate iron status at birth may prevent iron deficiency in early childhood.

OBJECTIVES

We aimed to identify predictors of serum ferritin (SF) and serum soluble transferrin receptor (sTfR) in healthy newborns and to relate these iron indexes to iron status in the first 2 y of life.

DESIGN

Using bivariate correlations and linear regression, we related various factors in pregnancy to SF (n=363) and sTfR (n=350) in healthy, term infants. Measurements of cord SF and sTfR were compared with those of SF and sTfR at 6, 12, and 24 mo. All 4 measurements were available for 191 and 169 infants for SF and sTfR, respectively.

RESULTS

Geometric mean (and 95% CI) cord SF and sTfR measurements were 159 (148, 171) microg/L and 7.3 (7.0, 7.6) mg/L, respectively. Cord SF correlated with sTfR (rho=-0.21, P<0.001). In regression analysis, cord SF correlated with smoking and the use of iron supplements during pregnancy (partial r=-0.12 and 0.16; P<0.05 for both). Cord sTfR was associated with first trimester BMI, gestational age, and male sex (partial r=0.30, 0.24, and 0.19, respectively; P<0.01 for all). Cord SF correlated with SF at 6, 12, and 24 mo (rho=0.45, 0.31, and 0.16 respectively; P<0.05 for all). At age 6 mo, 16 of 17 infants with SF <15 mug/L were boys.

CONCLUSIONS

Cessation of smoking and adequate iron prophylaxis during pregnancy may improve iron status in infancy. Cord SF is a predictor of iron status in the first 2 y of life. Boys are at particular risk of low iron status in early infancy.

The assessment of newborn iron stores at birth: a review of the literature and standards for ferritin concentrations

BACKGROUND

Serum ferritin measurements are used in clinical populations to estimate total body iron stores and the risk of subsequent iron deficiency or overload. The lack of normative newborn serum ferritin concentration data between 23 and 41 weeks has led to difficulty in establishing the incidence and degree of abnormal iron status in the neonatal period.

OBJECTIVES

The primary objective of this review was to summarize the maternal and gestational factors that determine ferritin concentrations in full-term and pre-term newborn infants and to generate comprehensive reference values. The secondary objective was to assess serum ferritin concentrations in newborn infants at risk for abnormal fetal iron metabolism, including maternal diabetes mellitus, intrauterine growth restriction and maternal smoking during pregnancy.

METHODS

Serum ferritin and gestational age data at birth from 457 low-risk pre-term and term infants of 23-41 weeks gestation obtained from 35 published studies reviewed from a period of 25 years and from recently collected data from our centers were assessed by regression analysis. Slopes and intercepts of the high-risk groups were compared with the standard curve.

RESULTS

Umbilical cord serum ferritin concentrations increased with advancing gestational age, from a mean of 63 mug/l at 23 weeks to 171 mug/l at 41 weeks gestation (p < 0.001). The infants of diabetic mothers had a lower intercept than the control infants (p < 0.001).

CONCLUSIONS

Iron deficiency and overload have been implicated in neurodevelopmental impairments. Normative cord serum ferritin data may permit a more precise assessment of infants who are at risk for abnormal iron status at birth.

Iron in fetal and neonatal nutrition

Both iron deficiency and iron excess during the fetal and neonatal period bode poorly for developing organ systems. Maternal conditions such as iron deficiency, diabetes mellitus, hypertension and smoking, and preterm birth are the common causes of perinatal iron deficiency. Long-term neurodevelopmental impairments and predisposition to future iron deficiency that are prevalent in infants with perinatal iron deficiency require early diagnosis, optimal treatment and adequate follow-up of infants at risk for the condition. However, due to the potential for oxidant-mediated tissue injury, iron overload should be avoided in the perinatal period, especially in preterm infants.

The relationship between red blood cell and reticulocyte indices and serum markers of iron status in the cord blood of newborns

BACKGROUND

The aims of this study were to assess the relationship between red blood cell and reticulocyte indices and biochemical iron status measurements, and to define reference values of these markers in the cord blood of newborns.

METHODS

In cord blood samples from 199 full-term newborns, cellular indices were assessed using an ADVIA 120 hematology system and iron status was analyzed by measurement of serum iron, transferrin, transferrin saturation (TfSat), transferrin receptor (TfR) and ferritin.

RESULTS

Cellular hemoglobin in red blood cells or reticulocytes was independent of serum iron markers such as TfSat, TfR and ferritin. The percentage of hypochromic red blood cells (%HYPOm) and reticulocytes (%HYPOr) correlated significantly with TfSat and TfR-F index (TfR/log ferritin). Importantly, %HYPOm and %HYPOr were also positively correlated with the high immature reticulocyte fraction (IRF-H) and the mean cell volume of red or reticulocytes.

CONCLUSIONS

In newborns, accelerated erythropoiesis is a major contributor to red blood cell and reticulocyte indices, which provide conflicting results when compared with serum markers of iron status. Apparently, the serum proteins ferritin, transferrin and TfR are more appropriate tools for the diagnosis of iron status in newborns.

Sub-optimal fetal iron acquisition under a maternal environment

Iron deficiency acquired at an early age can lead to significant developmental alterations. To evaluate the need for an interventional trial, we determined the iron reserves of neonates born to a group of women from an urban disadvantaged group. The influence of maternal iron on newborn hemoglobin, birth weight, and height was also analyzed. Hemoglobin and serum ferritin (SF) concentrations were measured at delivery on 201 neonates and their mothers. Neonatal iron stores were considered deficient when the cord SF concentration was <12.0 microg/L, reduced if > or =12.0 but <30 microg/L, and replenished when > or =30 microg/L. The same cut-offs applied to maternal SF values. Cord SF in the study group was 81.2 +/- 63 microg/L. Following the criteria adopted for this study, three groups of neonates were identified. I: 13 (6.5%) were born with deficient iron stores, II: 15 (7.5%) had reduced iron stores, and III: 173 (86%) had normal levels of storage iron. Cord SF concentrations were 7.1 +/- 3.5, 19.9 +/- 4.4 and 92 +/- 60 microg/L, respectively. Cord hemoglobin did not differ among groups. Iron stores at birth were reduced when maternal stores were deficient, reflecting a limited fetal iron-acquisition capacity and the restrictive effect of gestational iron deficiency on the constitution of adequate fetal iron reserves. These findings support the need for an interventional trial on the study population. Hemoglobin, birth weight, and height did not correlate with fetal or maternal iron stores.

Erythrocyte zinc protoporphyrin is elevated with prematurity and fetal hypoxemia

OBJECTIVE

To examine the utility of red blood cell (RBC) zinc protoporphyrin/heme ratio (ZnPP/H) as an indicator of fetal iron status, because unfavorable neurodevelopmental outcomes have been associated with poor iron status at birth, as indicated by low serum ferritin, and because few reliable indicators of fetal and early neonatal iron status exist.

METHODS

Consecutively studied preterm and term fetuses at delivery included the following groups: (1) control nonhypoxic, (2) fetuses with intrauterine growth retardation (IUGR), and (3) fetuses of insulin-treated mothers (FDM). We hypothesized (1) that rapid growth velocity associated with an accelerated erythropoiesis among normal fetuses will lead to reduced iron delivery to a rapidly expanding RBC mass and higher umbilical cord blood RBC ZnPP/H and (2) that fetuses that are exposed to pathologic hypoxemia will experience an additional increase in erythropoiesis and higher cord ZnPP/H. ZnPP/H was determined on saline-washed cord blood erythrocytes by hematofluorometry and was examined for its relationship with clinical factors and cord blood laboratory measurements indicative of tissue oxygenation (plasma erythropoietin [EPO] and reticulocyte count) and iron status (plasma ferritin and erythrocyte indices). Statistical testing included 1-way analysis of variance, 2-way analysis of variance with covariates, simple linear regression, and multiple regression analysis.

RESULTS

Among control group subjects, gestational age at birth was inversely correlated with RBC ZnPP/H and reticulocyte count and positively correlated with ferritin and EPO. Relative to control subjects, IUGR and FDM fetuses at specified gestational age groupings had higher ZnPP/H, lower plasma ferritin, and higher plasma EPO. Statistical modeling of the relationship between ZnPP/H and plasma ferritin among all study groups demonstrated significant impacts of gestational age, plasma EPO, maternal hypertension, and maternal smoking.

CONCLUSIONS

The inverse association of fetal ZnPP/H with gestational age at birth among control subjects is attributable to erythropoietic stimulation likely as a result of increasing growth velocity at the earliest gestational ages. The relatively higher ZnPP/H observed among fetuses in the IUGR and FDM groups likely is attributable to increased erythropoietic activity secondary to pathologic hypoxemia. Decreased placental iron transfer may also have limited iron availability and contributed to elevated ZnPP/H in the IUGR group. These data support the concept that increased erythropoietic activity and/or limited iron transport may place infants of diabetic mothers and infants with growth retardation at risk for developing systemic iron deficiency later in infancy and in early childhood.