Iron Absorption and Requirements in Pregnancy and Lactation

Study Overview
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Brief Summary
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Iron requirements increase significantly during pregnancy. Current recommendations for iron intake in pregnant and lactating women (PLW) are mainly based on factorial estimates and extrapolated from non-PLW. High-quality quantitative data on iron requirements in PLW are lacking, particularly in Sub- Saharan Africa where anaemia and infections are common. The primary objective of this study is to use the stable iron isotope technique to determine iron requirements and assess iron absorption and losses in PLW living in Kenya. In this prospective observational study, we will enrol pregnant women in the first trimester (n = 250) from a previous study cohort (n=1000) who participated in an iron absorption study at least 12 months ago and received the stable iron (Fe) isotope 57Fe. This 57Fe has now distributed and equilibrated throughout the women's body iron. Once enrolled in the present study, following Kenyan guidelines, women will receive standard prenatal care, including routine daily iron and folate supplementation. We will collect venous blood samples in each trimester and at delivery, and during the first 6 months of lactation in the mothers and infants (heel prick samples). To directly assess dietary iron absorption, in a randomly selected subset of women (n=35), oral and intravenous stable iron isotope tracers (54Fe, 58Fe) will be administered in the 2nd and 3rd trimesters.

Official Title
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Assessment of Iron Absorption and Requirements During Pregnancy and Lactation in Kenyan Women

Conditions
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Infancy, Iron Requirements, Pregnancy, Lactation, Iron Absorption

Intervention / Treatment
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* Other: CO-rebreathing
* Other: Oral iron isotope administration (54Fe)
* Other: Intravenous iron isotope administration (58Fe)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Providing consent to the informed consent form Participation in a previous stable isotope absorption study and having received an oral dose of 15 mg 57Fe at least 12 months prior to the date of inclusion in the study Positive pregnancy test and gestational age <10 weeks based on history of last menstrual period Permanent residence in the study area, and not expected to leave the study site for more than 4 weeks over the following 16 months Assessment of good health by professional staff at Msambweni Hospital Exclusion Criteria: Pre-pregnancy body mass index >30 kg/m2 Blood transfusion or intravenous iron treatment within 4 months of study start Major chronic infectious disease (e.g., tuberculosis, HIV+, hepatitis) Major chronic non-infectious disease (e.g., Type 1 or 2 diabetes, cancer)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| All participants<br>Women (n=250), are followed throughout their pregnancy. Mother-infant pairs are followed throughout the first 6-months postpartum. Women receive daily oral iron supplementation during pregnancy in accordance with local standards of care. Using the stable iron isotopes dilution methodology, concentration of the stable iron isotope tracer (57Fe) in circulation will be measured throughout pregnancy and up to 6 months postpartum in both, mother and infant. | Other: CO-rebreathing<br>* In the CO-rebreathing method, a dedicated apparatus is used for inhaling and rebreathing a very small bolus of CO through a spirometer for  2 min, which is absorbed through the lungs and binds to Hb, and then the increase of HbCO content of blood is measured 8 min after the CO inhalation. The increase of COHb in blood samples can then be used to precisely calculate Hb mass and blood volume<br>|
| Randomly selected sub-group<br>To directly assess dietary iron absorption, in a randomly selected subset of women (n=35), oral and intravenous stable iron isotope tracers (54Fe, 58Fe) will be administered. Oral iron absorption and erythrocyte iron incorporation will be measured 14 days after tracer administration. | Other: CO-rebreathing<br>* In the CO-rebreathing method, a dedicated apparatus is used for inhaling and rebreathing a very small bolus of CO through a spirometer for  2 min, which is absorbed through the lungs and binds to Hb, and then the increase of HbCO content of blood is measured 8 min after the CO inhalation. The increase of COHb in blood samples can then be used to precisely calculate Hb mass and blood volume<br>Other: Oral iron isotope administration (54Fe)<br>* Participants randomly assigned to the sub-group, will receive 54Fe with a test meal in the second and third trimester for assessment of dietary iron absorption<br>Other: Intravenous iron isotope administration (58Fe)<br>* Participants randomly assigned to the sub-group, will receive intravenous 58Fe in the second and third trimester for assessment of erythrocyte iron incorporation<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Iron absorbed, lossed and gained in the first trimester | isotope dilution | Change in 57Fe tracer abundance between gestational age 6, 10 and 15 weeks | 
| Iron absorbed, lossed and gained in the second trimester | isotope dilution | Change in 57Fe tracer abundance between gestational age 15, 20 and 25 weeks | 
| Iron absorbed, lossed and gained in the third trimester | isotope dilution | Change in 57Fe tracer abundance between gestational age 25, 30 and 35 weeks | 
| Iron absorbed, lossed and gained throughout pregnancy | isotope dilution | Change in 57Fe tracer abundance between gestational age 6, 10, 15, 20, 25, 30 and 35 weeks | 
| Iron absorbed, lossed and gained in lactating women | isotope dilution | Change in 57Fe tracer abundance between 6, 14 and 24 weeks postpartum | 
| Iron absorbed, lossed and gained in infancy | isotope dilution | Change in 57Fe tracer abundance between age 6, 14 and 24 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Fractional iron absorption (%) in the second trimester | shift in iron isotopic ratios | gestational age 20 weeks | 
| Fractional iron absorption (%) in the third trimester | shift in iron isotopic ratios | gestational age 30 weeks | 
| Erythrocyte iron incorporation (%) in the second trimester | shift in iron isotopic ratios | gestational age 20 weeks | 
| Erythrocyte iron incorporation (%) in the third trimester | shift in iron isotopic ratios | gestational age 30 weeks | 
| Hemoglobin concentration (g/dl) | Hb | gestational age 6 weeks | 
| Hemoglobin concentration (g/dl) | Hb | gestational age 10 weeks | 
| Hemoglobin concentration (g/dl) | Hb | gestational age 15 weeks | 
| Hemoglobin concentration (g/dl) | Hb | gestational age 20 weeks | 
| Hemoglobin concentration (g/dl) | Hb | gestational age 25 weeks | 
| Hemoglobin concentration (g/dl) | Hb | gestational age 30 weeks | 
| Hemoglobin concentration (g/dl) | Hb | gestational age 36 weeks | 
| Hemoglobin concentration (g/dl) | mother | 6 weeks postpartum | 
| Hemoglobin concentration (g/dl) | infant | age 6 weeks | 
| Hemoglobin concentration (g/dl) | mother | 14 weeks postpartum | 
| Hemoglobin concentration (g/dl) | infant | age 14 weeks | 
| Hemoglobin concentration (g/dl) | mother | 24 weeks postpartum | 
| Hemoglobin concentration (g/dl) | infant | age 24 weeks | 
| Mean corpuscular volume (fl) | MCV | gestational age 6 weeks | 
| Mean corpuscular volume (fl) | MCV | gestational age 10 weeks | 
| Mean corpuscular volume (fl) | MCV | gestational age 20 weeks | 
| Mean corpuscular volume (fl) | MCV | gestational age 30 weeks | 
| Mean corpuscular volume (fl) | mother | 6 weeks postpartum | 
| Mean corpuscular volume (fl) | infant | age 6 weeks | 
| Mean corpuscular volume (fl) | mother | 14 weeks postpartum | 
| Mean corpuscular volume (fl) | infant | age 14 weeks | 
| Mean corpuscular volume (fl) | mother | 24 weeks postpartum | 
| Mean corpuscular volume (fl) | infant | age 24 weeks | 
| Erythropoietin concentration (mU/ml) | EPO | gestational age 10 weeks | 
| Erythropoietin concentration (mU/ml) | EPO | gestational age 20 weeks | 
| Erythropoietin concentration (mU/ml) | EPO | gestational age 30 weeks | 
| Erythropoietin concentration (mU/ml) | EPO | 6 weeks postpartum | 
| Erythropoietin concentration (mU/ml) | EPO | 14 weeks postpartum | 
| Erythropoietin concentration (mU/ml) | EPO | 24 weeks postpartum | 
| Erythroferrone concentration (ng/ml) | ERFE | gestational age 10 weeks | 
| Erythroferrone concentration (ng/ml) | ERFE | gestational age 20 weeks | 
| Erythroferrone concentration (ng/ml) | ERFE | gestational age 30 weeks | 
| Erythroferrone concentration (ng/ml) | ERFE | 6 weeks postpartum | 
| Erythroferrone concentration (ng/ml) | ERFE | 14 weeks postpartum | 
| Erythroferrone concentration (ng/ml) | ERFE | 24 weeks postpartum | 
| Hepcidin concentration (ng/ml) | Hep | gestational age 10 weeks | 
| Hepcidin concentration (ng/ml) | Hep | gestational age 20 weeks | 
| Hepcidin concentration (ng/ml) | Hep | gestational age 30 weeks | 
| Hepcidin concentration (ng/ml) | Hep | 6 weeks postpartum | 
| Hepcidin concentration (ng/ml) | Hep | 14 weeks postpartum | 
| Hepcidin concentration (ng/ml) | Hep | 24 weeks postpartum | 
| Serum ferritin concentration (ug/l) | SF | gestational age 10 weeks | 
| Serum ferritin concentration (ug/l) | SF | gestational age 20 weeks | 
| Serum ferritin concentration (ug/l) | SF | gestational age 30 weeks | 
| Serum ferritin concentration (ug/l) | mother | 6 weeks postpartum | 
| Serum ferritin concentration (ug/l) | infant | age 6 weeks | 
| Serum ferritin concentration (ug/l) | mother | 14 weeks postpartum | 
| Serum ferritin concentration (ug/l) | infant | age 14 weeks | 
| Serum ferritin concentration (ug/l) | mother | 24 weeks postpartum | 
| Serum ferritin concentration (ug/l) | infant | age 24 weeks | 
| Soluble transferrin receptor concentration (ul/l) | sTfR | gestational age 10 weeks | 
| Soluble transferrin receptor concentration (ul/l) | sTfR | gestational age 20 weeks | 
| Soluble transferrin receptor concentration (ul/l) | sTfR | gestational age 30 weeks | 
| Soluble transferrin receptor concentration (ul/l) | mother | 6 weeks postpartum | 
| Soluble transferrin receptor concentration (ul/l) | infant | age 6 weeks | 
| Soluble transferrin receptor concentration (ul/l) | mother | 14 weeks postpartum | 
| Soluble transferrin receptor concentration (ul/l) | infant | age 14 weeks | 
| Soluble transferrin receptor concentration (ul/l) | mother | 24 weeks postpartum | 
| Soluble transferrin receptor concentration (ul/l) | infant | age 24 weeks | 
| C-reactive protein concentration (mg/l) | CRP | gestational age 10 weeks | 
| C-reactive protein concentration (mg/l) | CRP | gestational age 20 weeks | 
| C-reactive protein concentration (mg/l) | CRP | gestational age 30 weeks | 
| C-reactive protein concentration (mg/l) | mother | 6 weeks postpartum | 
| C-reactive protein concentration (mg/l) | infant | age 6 weeks | 
| C-reactive protein concentration (mg/l) | mother | 14 weeks postpartum | 
| C-reactive protein concentration (mg/l) | infant | age 14 weeks | 
| C-reactive protein concentration (mg/l) | mother | 24 weeks postpartum | 
| C-reactive protein concentration (mg/l) | infant | age 24 weeks | 
| alpha-glycoprotein concentration (mg/dl) | AGP | gestational age 10 weeks | 
| alpha-glycoprotein concentration (mg/dl) | AGP | gestational age 20 weeks | 
| alpha-glycoprotein concentration (mg/dl) | AGP | gestational age 30 weeks | 
| alpha-glycoprotein concentration (mg/dl) | mother | 6 weeks postpartum | 
| alpha-glycoprotein concentration (mg/dl) | infant | age 6 weeks | 
| alpha-glycoprotein concentration (mg/dl) | mother | 14 weeks postpartum | 
| alpha-glycoprotein concentration (mg/dl) | infant | age 14 weeks | 
| alpha-glycoprotein concentration (mg/dl) | mother | 24 weeks postpartum | 
| alpha-glycoprotein concentration (mg/dl) | infant | age 24 weeks | 
| Blood volume (l) |  | gestational age 10 weeks | 
| Blood volume (l) | BV | gestational age 20 weeks | 
| Blood volume (l) | BV | gestational age 30 weeks | 
| Blood volume (l) | BV | 6 weeks postpartum | 
| Blood volume (l) | BV | 14 weeks postpartum | 
| Blood volume (l) | BV | 24 weeks postpartum | 
| Intestinal fatty acid binding protein | I-FABP | gestational age 10 weeks | 
| Intestinal fatty acid binding protein | I-FABP | gestational age 20 weeks | 
| Intestinal fatty acid binding protein | I-FABP | gestational age 30 weeks | 
| Retinol binding protein | RBP | gestational age 10 weeks | 
| Retinol binding protein | RBP | gestational age 20 weeks | 
| Retinol binding protein | RBP | gestational age 30 weeks | 
| soluble CD14 | sCD14 | gestational age 10 weeks | 
| soluble CD14 | sCD14 | gestational age 20 weeks | 
| soluble CD14 | sCD14 | gestational age 30 weeks | 
| Insulin-like growth factor 1 | IGF-1 | gestational age 10 weeks | 
| Insulin-like growth factor 1 | IGF-1 | gestational age 20 weeks | 
| Insulin-like growth factor 1 | IGF-1 | gestational age 30 weeks | 
| Fibroblast growth factor 21 | FGF21 | gestational age 10 weeks | 
| Fibroblast growth factor 21 | FGF21 | gestational age 20 weeks | 
| Fibroblast growth factor 21 | FGF21 | gestational age 30 weeks |