LAUSR

The use of prophylactic antenatal corticosteroids (ACS)was arguably one of themost important advances in obstetric care to bemade during the second half of the 20th century, with clear benefits for babies born before 34+6weeks of gestation [1]. The 21st century has seen progressive expansion of the criteria for ACS use to includewomen at risk of late pre-term (35 to 36+ 6weeks of gestation) birth [2] andwomen having early term(37 to 38+ 6weeks of gestation) elective caesarean sections [3], although this is not universal.Womenhaving a planned induction of labour at 35 to 38 + 6 weeks of gestation are, however, not generally considered for ACS. Questions remain about the balance between the risks and benefits of ACS after 34 + 6 weeks of gestation as there are no data on long-term outcomes. There are also increasing concerns about the long-term outcomes for babies exposed to ACS before 34 + 6 weeks of gestation but subsequently delivered at term [4,5]. This more recent evidence reveals new unknowns about ACS, only some of which are currently being actively investigated. The benefits of ACS in babies born before 34+ 6 weeks of gestation are profound and include a reduction in rates of perinatal and neonatal mortality, respiratory distress syndrome (RDS), intraventricular haemorrhage, necrotizing enterocolitis and systemic infections in the first 48 h of life [1]. However, the majority of women given ACS do not deliver within the optimal window of between 24 h and 7 days of administration [6], and a large proportion deliver at term, where no benefits are anticipated. Combined with the current low threshold for ACS administration, this means that a large number of babies exposed to ACS before 34 + 6 weeks of gestation may not actually benefit from the intervention. There is increasing concern about the potential for harm in such babies [4,5]. A Finnish observational register-based study found that ACS exposure was associated with a reduction in birth weight, birth length and head circumference in babies subsequently born at pre-term, early-term and term gestations [4]. These findings on inutero growth are consistentwith reports from animal studies. In a Canadian population-based study, Melamed et al. [5] found an association between exposure to ACS during pregnancy and healthcare utilisation during childhood related to suspected neurocognitive and neurosensory disorders in babies born at term. While these data are concerning, they should not deter clinicians from offering ACS to women at increased risk of giving birth before 34 + 6 weeks of gestation. However, there is an urgent need for risk-assessment strategies to enable better targeting of ACS. Avenues to explore include digital tools supported by machine learning or artificial intelligence. The use of ACS after 34+6weeks of gestation is not universal. There is high-quality evidence that ACS between 34 + 0 and 36+ 6 weeks of gestation result in a reduced incidence of RDS, transient tachypnoea of