Risk factors for anemia of prematurity among 30-35-week preterm infants

Hiroki Kitaoka, Yoshihiko Shitara, Kohei Kashima, Shingo Ochiai, Hayato Chikai, Keiko Watanabe, Hiroto Ida, Tadayuki Kumagai, Naoto Takahashi

Author information
  • Hiroki Kitaoka

    Department of Pediatrics, Yaizu City Hospital
    Department of Pediatrics, The University of Tokyo Hospital

  • Yoshihiko Shitara

    Department of Pediatrics, The University of Tokyo Hospital

  • Kohei Kashima

    Department of Pediatrics, The University of Tokyo Hospital

  • Shingo Ochiai

    Department of Pediatrics, Yaizu City Hospital

  • Hayato Chikai

    Department of Pediatrics, Yaizu City Hospital
    Department of Neonatology, Tokyo Metropolitan Bokutoh Hospital

  • Keiko Watanabe

    Department of Pediatrics, Yaizu City Hospital

  • Hiroto Ida

    Department of Pediatrics, Yaizu City Hospital

  • Tadayuki Kumagai

    Department of Pediatrics, Yaizu City Hospital

  • Naoto Takahashi

    Department of Pediatrics, The University of Tokyo Hospital


Background: The risk factors for anemia of prematurity (AOP) among late preterm infants are unelucidated. We identified risk factors for declining hemoglobin (Hb) concentration and triggering factors for AOP treatment in infants born at 30-35 gestational weeks.

Methods: From 2012 to 2020, we conducted a single-center retrospective study of infants born at 30-35 weeks of gestation without congenital anomalies or severe hemorrhage. The primary outcome was AOP development, defined by initiation of treatments including red blood cell transfusion, subcutaneous injections of erythropoietin, and iron supplementation. A multivariable logistic regression model was used to investigate potential risk factors for AOP.

Results: A total of 358 infants were included. Lower gestational age (odds ratio, 0.19; 95% confidence interval 0.11-0.32), small for gestational age (SGA; 7.17, 2.15-23.9), low maternal Hb level before birth (0.66, 0.49-0.87), low Hb at birth (0.71, 0.57-0.89), and multiple large blood samplings (1.79; 1.40-2.29) showed significantly higher odds for AOP development.

Conclusions: Gestational age, SGA, low maternal Hb before birth, Hb at birth, and high number of large blood samplings were positively associated with AOP development in infants born at 30-35 gestational weeks.

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