en Pediatric Pediatric Original Research Original Research <p> <strong> Background </strong>:Identification of α thalassemia (α thal) a common cause of microcytosis during neonatal periods is an important step prevent unnecessary interventions. Thus, low the mean corpuscular volume (MCV) and the mean corpuscular hemoglobin (MCH) may consider as α-thalassemia key detection points. The present study aimed to determine the prevalence of microcytosis among neonates who born in Tehran, Iran. </p><p> <strong> Methods </strong>: Cord blood samples were collected from 1001 newborns after birth in labor room and their red blood cell parameters were investigated. </p><p> <strong> Results </strong>: MCV was 114.2 fl (95% CI: 113.5-114.9) and twenty three neonates (2.3%) had MCV less than 94 fL that classified as microcytosis and 4 (0.40%) had both low MCH and MCV. </p><p> <strong> Conclusion </strong>: Low MCV especially in normal Hb newborns may hints for α thal detection. </p> Thalassemia, mean corpuscular hemoglobin, microcytosis, HbBarts. 804 807 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1569-3&slc_lang=en&sid=1 Nasrin Khalesi nasrinkhalessi@yahoo.com 200319475328460013809 200319475328460013809 No Pediatrics Department, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran. Nastaran Khosravi nastarankhosravi@yahoo.com 200319475328460013810 200319475328460013810 No Pediatrics Department, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran. Mohammad Reza Rezaee nasrinkhalessi@yahoo.com 200319475328460013811 200319475328460013811 No Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Leila Amini amini.l@iums.ac.ir 200319475328460013812 200319475328460013812 Yes Midwifery Department, Faculty of Nursing & Midwifery, Iran University of Medical Sciences, Tehran, Iran.