In addition, low Hb may lead to chronic hypoxia which in turn may cause a stress response of increased placental corticotropin-releasing hormone secretion, inducing adverse consequences such as preterm birth, gestational hypertension and so forth.36 Nevertheless, the underlying biological mechanisms involved in the associations between maternal anaemia and preterm birth, low birth weight as well as SGA remain to be further elucidated. This evidence concerns the gene CRH and anemia (phenotype).