Improvements in maternal and neonatal health have been achieved over the past 30 years, which cannot guarantee a reduction in the incidence of preterm labor, but can cause significant changes in morbidity and fetal and neonatal survival. Premature labor is a partial common phenomenon that has been identified in 7–10% of all pregnant women (1). In this condition and to maximized fetal lung development, some conservative treatments are recommended in the last weeks of pregnancy. In this regard, the administration of glucocorticoids has played a pivotal role (2). Reducing the incidence of neonatal respiratory distress syndrome (RDS) by up to 50% after glucocorticoid administration has been shown for the first time by Liggins and Hawie (3). Taking corticosteroids between 34 to 36 weeks of gestation promotes fetal lung development, increases neonatal Apgar score, and reduces the likelihood of RDS (4, 5). Additionally, treatment with glucocorticoids in such pregnancies can reduce neonatal mortality and morbidity due to reducing the risk for intraventricular hemorrhage, necrotizing enterocolitis, decrease the need for intensive care unit cares, and increase the risk of sepsis in the first 48 hours of neonatal life (6–8). Human studies have also shown that betamethasone used during pregnancy can potentially affect placental function, fetal growth, hypothalamic-pituitary-adrenal axis development, and endocrine stress responses during infancy (9–12). In the fetal period, prenatal use of betamethasone in pregnant women whose fetuses are stunted has resulted in a transient improvement in blood flow to the uterus and umbilical arteries (13). Moreover, corticosteroids in women at high risk for preterm delivery further improve the neurodevelopmental condition of those born before 34 weeks of gestation (14).
In general, prenatal glucocorticoids are widely used in pregnancies that are prone to preterm delivery. In particular, the use of these medications was common since 1994 after a conference hosted by the National Institutes of Health, because there was strong evidence that glucocorticoids prescribed before 34 weeks of gestation in women at risk for preterm birth could reduce adverse neonatal outcomes (14). But the effects of these drugs on late preterm infants (after the 34th week of gestation) remained unknown (15). It was believed that after about 34 to 35 weeks of pregnancy, most fetuses develop and their survival at this age differs only 1% from that of full-term infants (16). However, it is now clear those infants born during the late preterm have more infant and childhood problems than term infants. For this reason, this question remains unanswered whether prenatal glucocorticosteroid administration is beneficial in this population. Therefore, in this study, we decided to evaluate the effects of betamethasone administration on the clinical condition of the late preterm infants born between 34 and 36 weeks of gestation.