Iron Status of Non-anemic Pregnant Women in First Trimester

1. Title Reference Intervals of Iron, Ferritin, TIBC, and Transferrin Saturation in First Trimester Pregnant Women and Prevalence of Non-Anemic Iron Deficiency 2. Background and Rationale Iron deficiency (ID) is the most common micronutrient deficiency globally and a significant concern during pregnancy. Early identification of iron deficiency-even in the absence of anemia-is essential to prevent adverse maternal and fetal outcomes. However, reference intervals for iron biomarkers in early pregnancy remain inconsistent and vary across populations. Moreover, there is a paucity of data on the prevalence of non-anemic iron deficiency (NAID) during the first trimester, a critical period for fetal development. This study aims to address these gaps. 3. Objectives Primary Objective: To determine reference intervals for serum iron, ferritin, TIBC, and TSAT in healthy pregnant women during the first trimester.

Secondary Objective: To estimate the prevalence of non-anemic iron deficiency (NAID), defined as low iron biomarkers with normal hemoglobin (Hb ≥ 11 g/dL). 4. Study Design Type: Cross-sectional observational study Setting: Antenatal care clinics at Hung Vuong Hospital, Ho Chi Minh city, Vietnam Duration: From March to June, 2025 (anticipated) 5. Study Population Inclusion Criteria

* Pregnant women in the first trimester (gestational age ≤ 13 weeks 6 days). * Carrying a single live fetus. * Hemoglobin ≥ 11 g/dL at the time of enrollment. * Systolic blood pressure \< 140 mmHg and diastolic \< 90 mmHg. * Body temperature \> 35°C and \< 37.5°C at time of examination. * Attending routine antenatal care and willing to participate. Exclusion Criteria * History of:

Diabetes mellitus, hypertension, hemoglobinopathies, leukemia, non-hematologic malignancies, systemic lupus erythematosus. Gastrointestinal disorders affecting iron absorption (e.g., Celiac disease, Crohn's disease, ulcerative colitis, gastric surgery). * Current use of acid-suppressing medications (PPIs, H2 blockers). * Positive screening for Treponema pallidum, HBsAg, or HIV. * Use of stimulants or tobacco smoking. 6. Sample Size A minimum of 120 participants is recommended for establishing reference intervals per CLSI guidelines (C28-A3), with oversampling to account for exclusions and incomplete data. 7. Data Collection Clinical Data

* Maternal age, gestational age, BMI * Vital signs (BP, temperature) * Medical and obstetric history Laboratory Investigations * Hemoglobin (Hb) * Serum iron * Ferritin * Total iron-binding capacity (TIBC) * Transferrin saturation (TSAT) = (Serum iron / TIBC) × 100 8. Statistical Analysis Reference Intervals

* Outlier detection using Dixon-Reed methods * Calculation of 2.5th-97.5th percentiles (non-parametric method) Prevalence of NAID * Defined as ferritin \< 15 ng/mL or TSAT \< 20% with Hb ≥ 11 g/dL (or more cutoffs to present a wide variety of prevalences of NAID). Reported as frequency and percentage with 95% confidence intervals Software * Statistical analysis will be performed using Jupyter Notebook (python programming language) 9. Ethical Considerations

* Ethical approval will be obtained from the Institutional Review Board. * Written informed consent will be obtained from all participants. * Data confidentiality will be strictly maintained. 10. Significance The findings will provide local reference standards for iron parameters during early pregnancy and help clinicians better detect and manage iron deficiency before the onset of anemia. This is critical for optimizing maternal and fetal health outcomes and future study to determine best intervention for NAID patients.