Description:

This chapter on therapeutic drift with antenatal steroids will make the case that this pilar of treatment to improve the outcomes of preterm infants, despite multiple Randomized Control Trials (RCTs) and meta-analysis, has multiple gaps in solid clinical data to support any expanded use of Antenatal Corticosteroids (ACS). A basic problem is that agents used for ACS have never been evaluated to minimize fetal exposures. Based on the premise that all drug exposure to the fetus should be minimized and only used when necessary, ACS is a potent developmental modulator that has never been evaluated to minimize the dose and duration of fetal exposure. The use of ACS is expanding to late preterm infants where the benefit is modest, to elective C-sections, and periviable fetuses, with minimal RCT data of long-term benefit. Relevant animal experiments demonstrate that much lower doses will induce lung maturation in sheep and primates. Another area of drift in the use of ACS is based on the assumption that the old RCT data accurately predict the magnitude of benefit when ACS is used today with entirely different OB and neonatal care strategies to improve outcomes. We do not have data that demonstrate the effectiveness of ACS in very low resource environments, where most of the preterm mortality occurs. The final concern is the risk of ACS to the infant and child. Short-term risks are minimal but dysmaturation effects of ACS on multiple organ systems (lung, heart, brain, and kidney) may result in disease presentation in later life.

Neurotrophins are proteins critically involved in neural growth, survival and differentiation, and therefore important for fetal brain development. Reduced cord blood neurotrophins have been observed in very preterm infants (< 32 weeks gestation) who subsequently develop brain injury. Antenatal steroid exposure can alter neurotrophin concentrations, yet studies to date have not examined whether this occurs in the late preterm infant (33–36 weeks gestation), despite increasing recognition of subtle neurodevelopmental deficits in this population. Antenatal corticosteroids are among the most important and widely used interventions to improve outcomes for preterm infants. Antenatal corticosteroid dosing regimens remain unoptimized and without maternal weight-adjusted dosing. We, and others, have hypothesized that, once a low concentration of maternofetal steroid exposure is achieved and maintained, the duration of the steroid exposure determines treatment efficacy. Using a sheep model of pregnancy, we tested the relationship among steroid dose, duration of exposure, and treatment efficacy.

With Regards
Johansan
Journal Coordinator
Global Journal of Research and Review