The Effect of Low Doses of Intermediate Acting Corticosteroids on the Prolongation of Pregnancy in Threatened Preterm Birth

Prematurity is the leading cause of infant mortality and is associated with an increased risk of respiratory, neurological and metabolic disorders in survivors. Approximately 15 million babies are born preterm annually worldwide. Despite the rapid development of pharmacotherapy, there was no significant decline in premature birth (PTB) rates. So far, the most useful intervention for improving neonatal outcomes in premature children has been the antenatal administration of long-acting corticosteroids (CSs). Although the underlying causes of PTB are numerous, it is well established that infection and inflammation represent a highly significant risk factor for spontaneous PTB, characterized by the significant production of inflammatory mediators that lead to the weakening of the foetal membranes, cervical stroma and contraction of the myometrium. There is increasing evidence of the presence of sterile inflammation (intra-amniotic inflammation without the presence of microorganisms) in PTB with both intact membranes and preterm premature rupture of membranes (PPROM). CS and non-steroidal anti-inflammatory drugs (NSAID) are used today to treat most inflammatory diseases. NSAIDs are used as tocolytics. Indomethacin, one of the most commonly used NSAID tocolytics, has been associated with oligohydramnios and premature closure of the foetal ductus arteriosus when used for prolonged periods. As far back as 1972, Liggins and Howie proved that antenatal administration of CS reduces the incidence and severity of respiratory distress syndrome (RDS) and mortality of premature infants. Meta-analyses have confirmed a lower rate of intraventricular haemorrhage and necrotic enterocolitis in premature infants whose mothers received RDS prophylaxis. Therefore, their application proved to be the most useful intervention for improving neonatal outcomes in threatening PTB. Today, CS is a part of standard therapy for treating systemic autoimmune diseases and acts as a suppressor of immune response. Long acting CSs cross the placental barrier and are used to treat the foetus (foetal lupus, congenital adrenal hyperplasia, prevention of respiratory distress syndrome), and intermediate acting drugs are used to treat maternal diseases as they have a low affinity for passing through the placenta. The effect of low doses of intermediate acting corticosteroids on the prolongation of pregnancy in threatened preterm birth has not yet been studied. Given that PTB is a syndrome characterized by a strong inflammatory response, we present the hypothesis that low doses of an intermediate acting CS for 3 weeks after tocolysis and RDS prophylaxis help prolong singleton pregnancy in women with threatening PTB, without harmful consequences for mother and child.