Betamethasone for Preterm Birth: Auckland Steroid Trial Full Results and New Insights 50 Years on

A review of the potential off-target effects of antenatal steroid exposures on fetal development

Antenatal steroids (ANS) are one of the most widely prescribed medications in pregnancy, being administered to women at risk of preterm delivery. In the setting of preterm delivery at or below 35 weeks' gestation, systematic review data show ANS reduce perinatal morbidity and mortality, primarily by promoting fetal lung maturation. However, with the expanding use of this intervention has come a growing appreciation for the potential off-target, adverse effects of ANS therapy on wider fetal development. We undertook a narrative literature review of the animal and clinical literature to assess current evidence for adverse effects of ANS exposure and fetal development. This review presents a summary of the evidence relating to the potential for wide-ranging, off-target, adverse effects of ANS therapy on fetal development and programming. We highlight an urgent need for further animal and clinical studies investigating the effects of ANS on the fetal immune, cardiovascular, renal and hepatic systems given a current sparsity of evidence. We also strongly suggest an emphasis on open disclosure, discussion and education of clinicians and patients with regard to the potential benefits and risks of ANS therapy, particularly in late preterm and term gestations where infants derive relatively few benefits from these drugs. We also propose further studies on the optimisation of ANS therapy through improved patient selection and improved dosing regimens based on a pharmacokinetic-pharmacodynamic informed understanding of ANS action on the fetal lung.

Single-nucleotide polymorphisms in dizygotic twin ovine fetuses are associated with discordant responses to antenatal steroid therapy

BACKGROUND

Antenatal steroid (ANS) therapy is given to women at risk of preterm delivery to accelerate fetal lung maturation. However, the benefit of ANS therapy is variable and how maternal and fetal factors contribute to this observed variability is unknown. We aimed to test the degree of concordance in preterm lung function, and correlate this with genomic, transcriptomic, and pharmacokinetic variables in preterm dizygotic twin ovine fetuses.

METHODS

Thirty-one date-mated ewes carrying twin fetuses at 123 ± 1 days' gestation received maternal intramuscular injections of either (i) 1 × 0.25 mg/kg betamethasone phosphate and acetate (CS1, n = 11 twin pairs) or (ii) 2 × 0.25 mg/kg betamethasone phosphate and acetate, 24 h apart (CS2, n = 10 twin pairs) or (iii) 2 × saline, 24 h apart (negative control, n = 10 twin pairs). Fetuses were surgically delivered 24 h after their final treatment and ventilated for 30 min.

RESULTS

ANS-exposed female fetuses had lower arterial partial pressure of carbon dioxide (PaCO2) values than male fetuses (76.5 ± 38.0 vs. 97.2 ± 42.5 mmHg), although the observed difference was not statistically significant (p = 0.1). Only 52% of ANS-treated twins were concordant for lung maturation responses. There was no difference in fetal lung tissue or plasma steroid concentrations within or between twin pairs. Genomic analysis identified 13 single-nucleotide polymorphisms (SNPs) statistically associated with ANS-responsiveness, including in the proto-oncogene MET and the transcription activator STAT1.

CONCLUSIONS

Twin fetal responses and ANS tissue levels were comparable with those from singleton fetuses in earlier studies. Twin ovine fetuses thus benefit from ANS in a similar manner to singleton fetuses, and a larger dose of betamethasone is not required. Assuming no difference in input from the placental or maternal compartments, fetal lung responses to ANS therapy in dizygotic twin preterm lambs are dependent on the fetus itself. These data suggest a potential heritable role in determining ANS responsiveness.

Comparison of outcomes of the 50-year follow-up of a randomized trial assessed by study questionnaire and by data linkage: The CONCUR study

BACKGROUND/AIMS

Self-reported questionnaires on health status after randomized trials can be time-consuming, costly, and potentially unreliable. Administrative data sets may provide cost-effective, less biased information, but it is uncertain how administrative and self-reported data compare to identify chronic conditions in a New Zealand cohort. This study aimed to determine whether record linkage could replace self-reported questionnaires to identify chronic conditions that were the outcomes of interest for trial follow-up.

METHODS

Participants in 50-year follow-up of a randomized trial were asked to complete a questionnaire and to consent to accessing administrative data. The proportion of participants with diabetes, pre-diabetes, hyperlipidaemia, hypertension, mental health disorders, and asthma was calculated using each data source and agreement between data sources assessed.

RESULTS

Participants were aged 49 years (SD = 1, n = 424, 50% male). Agreement between questionnaire and administrative data was slight for pre-diabetes (kappa = 0.10), fair for hyperlipidaemia (kappa = 0.27), substantial for diabetes (kappa = 0.65), and moderate for other conditions (all kappa >0.42). Administrative data alone identified two to three times more cases than the questionnaire for all outcomes except hypertension and mental health disorders, where the questionnaire alone identified one to two times more cases than administrative data. Combining all sources increased case detection for all outcomes.

CONCLUSIONS

A combination of questionnaire, pharmaceutical, and laboratory data with expert panel review were required to identify participants with chronic conditions of interest in this follow-up of a clinical trial.

Adapt to survive and thrive: the time is now for adaptive platform trials for preterm birth

In this Viewpoint, we discuss the challenges facing perinatal clinical researchers, many of which are unique to this field, and how traditional two-arm randomised trials using frequentist analysis might no longer be fit for purpose for perinatology. We propose a solution: the adoption of adaptive platform trials (APTs) with Bayesian methodology to address perinatal research questions to improve outcomes of preterm birth. APTs use a master protocol as a foundation to efficiently assess multiple interventions simultaneously for a particular disease. APTs can study these interventions in a perpetual manner, with interventions allowed to enter or leave the platform on the basis of preplanned decision algorithms. In this Viewpoint, we outline the ways in which APTs can overcome some of the issues facing perinatal clinical research, and the challenges and essential requirements for the design and implementation of perinatal APTs that should be considered.

Reproductive outcomes after antenatal corticosteroids: Secondary analysis of 50-year follow-up of the Auckland steroid randomized trial

INTRODUCTION

Antenatal corticosteroids are widely used to prevent morbidity and mortality after preterm birth, but there are ongoing concerns about the possible risk of long-term adverse effects, including perturbation of endocrine systems, with potential implications for reproduction. A small number of animal studies have suggested possible adverse effects on reproduction after antenatal exposure to corticosteroids, but there is a paucity of human data.

MATERIAL AND METHODS

This is a secondary cohort analysis of the 50-year follow-up of the Auckland Steroid Trial (1969-1974) comparing antenatal exposure to corticosteroids or placebo. Participants whose mothers took part in the placebo-controlled randomized trial of antenatal corticosteroids completed a questionnaire reporting reproductive outcomes at 50 years of age. The main outcome was at least one pregnancy ≥20 weeks or fathered at least one pregnancy ≥20 weeks. Additional outcomes included a number of pregnancies or fathered pregnancies ≥20 weeks, outcomes relating to female reproductive lifespan (including age at menarche and menopause), and outcomes relating to their offspring (including birthweight and gestation).

RESULTS

Of 917 eligible participants, 415 (45% of eligible) completed the questionnaire at a mean (SD) age of 49.3 (1.0) years. The proportion of participants who had experienced at least one pregnancy ≥20 weeks or fathered at least one pregnancy ≥20 weeks was similar in betamethasone and placebo-exposed groups (163/217 [75%] vs. 136/190 [72%]; RR 1.08, (95% CI 0.95 to 1.22); p = 0.23). Participants exposed to betamethasone had a slightly higher number of pregnancies or fathered pregnancies ≥20 weeks compared to those exposed to placebo (mean 1.89 vs. 1.60; marginal mean difference 0.20, (95% CI 0.03-0.37); p = 0.03). Other outcomes, including female reproductive lifespan and offspring-related outcomes, were similar in both randomized groups. There were also no differences in any outcomes between those born preterm and those born at term.

CONCLUSIONS

Antenatal exposure to corticosteroids appears to have no clinically important effect on reproductive outcomes to 50 years.

General health and social outcomes 50 years after exposure to antenatal betamethasone: follow-up of a randomised controlled trial

BACKGROUND

Antenatal corticosteroids are recommended for women at risk of preterm birth from 24 to 34 weeks' gestation as they reduce neonatal morbidity and mortality, but evidence regarding their long-term effects on offspring is limited. This study assessed general health and social outcomes 50 years after antenatal exposure to corticosteroids.

METHODS

We assessed 424 adult offspring of women who participated in the first randomised, double-blind, placebo-controlled trial of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome. The first 717 mothers received two intramuscular injections of betamethasone (6 mg betamethasone sodium phosphate and 6 mg betamethasone acetate) or placebo given 24 h apart and the subsequent 398 received two injections of double dose betamethasone (12 mg betamethasone sodium phosphate and 12 mg betamethasone acetate) or equivalent volume of placebo. Follow-up included a health questionnaire and consent for access to administrative data sources. Outcome categories included mental health (depression, anxiety, bipolar affective disorder, schizophrenia and treatment or hospital admission for any mental health disorder), general health (chronic kidney disease, cancer diagnosis, bone fracture, oral health, allergies, functional difficulties and physical activity) and social outcomes (educational attainment, employment and criminal convictions). Investigators remained blinded to treatment allocation. Analyses were adjusted for gestational age at entry, sex and clustering.

RESULTS

We assessed 424 adult offspring (46% of survivors; mean [SD] age 49.3 [1.0] years; 212 [50%] female). There was no difference in mental health, general health and social outcomes between those exposed to betamethasone and those exposed to placebo, with the exception that osteoporotic site fracture in adulthood was more likely to have occurred in the betamethasone group compared with placebo (adjusted relative risk 1.57, 95% CI 1.00, 2.48, p = 0.05). No dose-effect relationship was evident and there was no difference in the proportion with at least one fracture. Follow-up rate and lack of in-person assessments were the main limitations.

CONCLUSIONS

There is no evidence that antenatal corticosteroids have clinically important effects on general health and social outcomes up to 50 years of age.

Cardiovascular outcomes 50 years after antenatal exposure to betamethasone: Follow-up of a randomised double-blind, placebo-controlled trial

BACKGROUND

Antenatal corticosteroids for women at risk of preterm birth reduce neonatal morbidity and mortality, but there is limited evidence regarding their effects on long-term health. This study assessed cardiovascular outcomes at 50 years after antenatal exposure to corticosteroids.

METHODS AND FINDINGS

We assessed the adult offspring of women who participated in the first randomised, double-blind, placebo-controlled trial of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome (RDS) (1969 to 1974). The first 717 mothers received 2 intramuscular injections of 12 mg betamethasone or placebo 24 h apart and the subsequent 398 received 2 injections of 24 mg betamethasone or equivalent volume of placebo. Follow-up included a health questionnaire and consent to access administrative data sources. The co-primary outcomes were the prevalence of cardiovascular risk factors (any of hypertension, hyperlipidaemia, diabetes mellitus, gestational diabetes mellitus, or prediabetes) and age at first major adverse cardiovascular event (MACE) (cardiovascular death, myocardial infarction, coronary revascularisation, stroke, admission for peripheral vascular disease, and admission for heart failure). Analyses were adjusted for gestational age at entry, sex, and clustering. Of 1,218 infants born to 1,115 mothers, we followed up 424 (46% of survivors; 212 [50%] female) at mean (standard deviation) age 49.3 (1.0) years. There were no differences between those exposed to betamethasone or placebo for cardiovascular risk factors (159/229 [69.4%] versus 131/195 [67.2%]; adjusted relative risk 1.02, 95% confidence interval [CI] [0.89, 1.18;]; p = 0.735) or age at first MACE (adjusted hazard ratio 0.58, 95% CI [0.23, 1.49]; p = 0.261). There were also no differences in the components of these composite outcomes or in any of the other secondary outcomes. Key limitations were follow-up rate and lack of in-person assessments.

CONCLUSIONS

There is no evidence that antenatal corticosteroids increase the prevalence of cardiovascular risk factors or incidence of cardiovascular events up to 50 years of age. Established benefits of antenatal corticosteroids are not outweighed by an increase in adult cardiovascular disease.

Antenatal corticosteroids: an updated assessment of anticipated benefits and potential risks

Antenatal steroid therapy is increasingly central to the obstetrical management of women at imminent risk of preterm birth. For women likely to deliver between 24 and 34 weeks' gestation, antenatal steroid therapy is the standard of care, conferring sizable benefits and few risks in high-resource environments when appropriately targeted. Recent studies have focused on antenatal steroid use in periviable and late preterm populations, and in term cesarean deliveries. As a result, antenatal steroid therapy has now been applied from 22 to 39+6 weeks of estimated gestational age. There is also an increased appreciation that the vast majority of randomized control data informing the use of antenatal steroids are derived from predominantly high-resource, White populations. Accordingly, a sizable amount of work has recently been undertaken to test how to safely use antenatal steroids in low- and middle-resource environments, wherein the often high rates of preterm birth make these low-cost, easily administered interventions an attractive proposition. It is likely underappreciated by the obstetrical and neonatal communities that the overall efficacy of antenatal steroid therapy is highly variable (including when preterm risk is accurately assessed), the treatment regimens used are largely arbitrary, dosing is suprapharmacologic for effect, and the benefit-risk balance is significantly and differentially modified by gestation. It is also very likely that the patients consenting to receive these treatments are similarly unaware of the complex balance of potential benefits and harms. Although a small number of follow-up studies present a generally benign picture of long-term antenatal steroid risk, several large, population-based retrospective studies have identified associations between antenatal steroid use, childhood mental disease, and newborn infections that warrant urgent attention. Of particular contemporary importance are emergent efforts to optimize antenatal steroid regimens on the basis of the pharmacokinetics and pharmacodynamics of the agents themselves, the need for better targeting of these potent drugs, and clear articulation of the potential benefits and harms of antenatal steroid use at differing stages of pregnancy and in different delivery contexts.

Respiratory benefit in preterm lambs is progressively lost when the concentration of fetal plasma betamethasone is titrated below two nanograms per milliliter

Antenatal steroid therapy is the standard of care for women at imminent risk of preterm delivery. Current dosing regimens use suprapharmacological doses to achieve extended fetal steroid exposures. We aimed to determine the lowest fetal plasma betamethasone concentration sufficient to achieve functional preterm lung maturation. Ewes with single fetuses underwent surgery to install a fetal jugular catheter. Adopting a stepwise design, ewes were randomized to either a saline-only group (negative control group; n = 9) or one of four betamethasone treatment groups. Each betamethasone group fetus received a fetal intravenous infusion to target a constant plasma betamethasone level of either 1) 2 ng/mL (2 ng/mL positive control group, n = 9); 2) 1 ng/mL, (1 ng/mL group, n = 10); 3) 0.5 ng/mL (0.5 ng/mL group, n = 10); or 4) 0.25 ng/mL (0.25 ng/mL group, n = 10). Fetuses were infused for 48 h, delivered, and ventilated. The positive control group, negative control group, and mid-point 0.5 ng/mL group animals were tested first. An interim analysis informed the final betamethasone group tested. Positive control group animals had large, statistically significant improvements in respiratory function. Based on an interim analysis, the 1.0 ng/mL group was studied in favor of the 0.25 ng/mL group. Treatment efficacy was progressively lost at plasma betamethasone concentrations lower than 2 ng/mL. We demonstrated that the acute respiratory benefit conveyed by antenatal steroid exposure in the fetal sheep is progressively lost when constant fetal plasma betamethasone concentrations are reduced below a targeted value of 2 ng/mL.NEW & NOTEWORTHY Lung maturation benefits in preterm lambs were progressively lost when fetal plasma betamethasone concentrations fell below 2 ng/mL. The effective floor threshold for a robust, lung-maturing exposure likely lies between 1 and 2 ng betamethasone per milliliter of plasma. Hypothalamic pituitary adrenal axis signaling and immunocyte populations remained materially disrupted at subtherapeutic steroid concentrations. These data demonstrate the potential to improve antenatal steroid therapy using reduced dose regimens informed by glucocorticoid pharmacokinetics and pharmacodynamics.