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Treatment with antenatal steroids (ANS) is standard practice for reducing the risk of respiratory distress in the preterm infant. Despite clear overall benefits when appropriately administered, many fetuses fail to derive benefit from ANS therapies. In standardized experiments using a pregnant sheep model, we have demonstrated that around 40% of ANS-exposed lambs did not have functional lung maturation significantly different from that of saline-treated controls. Surfactant protein A is known to play an important role in lung function. In this genotyping study, we investigated the potential correlation between polymorphisms in SFTPA1, messenger RNA and protein levels, and ventilation outcomes in animals treated with ANS. 45 preterm lambs were delivered 48 h after initial ANS therapy and 44 lambs were delivered 8 days after initial ANS therapy. The lambs were ventilated for 30 min after delivery. SFTPA1 mRNA expression in lung tissue was not correlated with arterial blood PaCO2 values at 30 min of ventilation in lambs delivered 48 h after treatment. SFTPA1 protein in lung tissue was significantly correlated with PaCO2 at 30 min of ventilation in lambs ventilated both 48 h and 8 days after ANS treatment. Six different single nucleotide polymorphisms (SNPs) in the Ovis aries SFTPA1 sequence were detected by Sanger Sequencing. No individual SNPs or SNP haplotypes correlated with alterations in PaCO2 at 30 min of ventilation or SFTPA1 protein levels in the lung. For the subset of animals analyzed in the present study, variable lung maturation responses to ANS therapy were not associated with mutations in SFTPA1.

Antenatal steroid (ANS) therapy is the standard care for women at imminent risk of preterm labor. Despite extensive and long-standing use, 40%–50% of babies exposed antenatally to steroids do not derive benefit; remaining undelivered 7 days or more after ANS treatment is associated with a lack of treatment benefit and increased risk of harm. We used a pregnant sheep model to evaluate the impact of continuous versus pulsed ANS treatments on fetal lung maturation at an extended, 8-day treatment to delivery interval. Continuous low-dose ANS treatments for more than 72 h in duration improved fetal lung maturation at 8 days after treatment initiation. If fetal ANS exposure was interrupted, the beneficial ANS effect was lost. Truncated treatments, including that simulating the current clinical treatment regimen, did not improve lung function. Variable fetal lung maturation was correlated to the amount of saturated phosphatidylcholine present in the lung fluid. These data demonstrate that 1) the durability of ANS therapy may be enhanced by employing an extended, low-dose treatment regimen by reducing total dose and 2) interrupting the continuity of fetal exposure by allowing it to fall below a minimal threshold was associated with comparably poor functional maturation of the preterm ovine lung.

Antenatal steroids (ANSs) are routinely administered to women judged to be at imminent risk of preterm delivery. Their principal benefit is precocious functional maturation of the preterm fetal lung. Current dosing regimens expose the mother and fetus to high steroid levels that may be unnecessary, increasing the potential risks of disruption to the maternal and fetal hypothalamic-pituitary-adrenal (HPA) axis and glucose regulation, alterations in placental function, and reduced fetal growth. Using a sheep model of pregnancy, we tested the hypothesis that direct fetal administration of an ultra-low dose course of betamethasone phosphate (∼0.33 mg) would be sufficient to elicit functional maturation of the fetal lung. A jugular catheter was installed in singleton ovine fetuses at 122-day gestation under general anesthesia. Animals were randomized to receive either: 1) fetal intravenous betamethasone phosphate to target fetal plasma betamethasone mean levels of 2 ng/mL for 26 h (fetal treatment group; n = 16); 2) fetal intravenous saline for 26 h and two maternal intramuscular injections of 0.25 mg/kg betamethasone phosphate + betamethasone acetate, simulating a standard clinical treatment (maternal treatment group; n = 12); or 3) fetal intravenous saline only for 26 h (negative control group; n = 10). Fetuses were delivered 48 h after surgery, ventilated for 30 min to allow the collection of lung function and physiological data, and euthanized. Quantitative PCR and Western blots were used to assess markers of lung maturation. The average total betamethasone phosphate dose for the fetal treatment group was 1% (0.3 mg) of the maternal treatment group (31-mg betamethasone phosphate + betamethasone acetate). At 30 min of ventilation, arterial PaCO2, pH, heart rate, and ventilation efficacy index (VEI) were significantly (P < 0.05) and equivalently improved in both the fetal treatment group and maternal treatment group, relative to the negative control group. Similarly, S

Background Intraamniotic inflammation is associated with up to 40% of preterm births, most notably in deliveries occurring prior to 32 weeks’ gestation. Despite this, there are few treatment options allowing the prevention of preterm birth and associated fetal injury. Recent studies have shown that the small, non-competitive allosteric interleukin (IL)-1 receptor inhibitor, rytvela, may be of use in resolving inflammation associated with preterm birth (PTB) and fetal injury. We aimed to use an extremely preterm sheep model of chorioamnionitis to investigate the anti-inflammatory efficacy of rytvela in response to established intra-amniotic (IA) lipopolysaccharide (LPS) exposure. We hypothesized that rytvela would reduce LPS-induced IA inflammation in amniotic fluid (AF) and fetal tissues. Methods Sheep with a single fetus at 95 days gestation (estimated fetal weight 1.0 kg) had surgery to place fetal jugular and IA catheters. Animals were recovered for 48 hours before being randomized to either: i) IA administration of 2 ml saline 24 hours before 2 ml IA and 2 ml fetal intravenous (IV) administration of saline (Saline Group, n = 7); ii) IA administration of 10 mg LPS in 2 ml saline 24 hours before 2 ml IA and 2 ml fetal IV saline (LPS Group, n = 10); 3) IA administration of 10 mg LPS in 2 ml saline 24 hours before 0.3 mg/fetal kg IA and 1 mg/fetal kg fetal IV rytvela in 2 ml saline, respectively (LPS + rytvela Group, n = 7). Serial AF samples were collected for 120 h. Inflammatory responses were characterized by quantitative polymerase chain reaction (qPCR), histology, fluorescent immunohistochemistry, enzyme-linked inmmunosorbent assay (ELISA), fluorescent western blotting and blood chemistry analysis. Results LPS-treated animals had endotoxin and AF monocyte chemoattractant protein (MCP)-1 concentrations that were significantly higher at 24 hours (immediately prior to rytvela administration) relative to values from Saline Group animals. Following rytvela administr

Background Antenatal corticosteroid (ACS) therapy is standard of care for women at imminent risk of preterm labour. Despite this, much remains to be understood regarding an optimal (maximum benefit, minimal risk of side effects) ACS dosing strategy. Although conveying overall benefit when given to the right patient at the right time, ACS treatment efficacy is highly variable, and is not risk-free. Building on earlier findings, we hypothesized that when administered in combination with slow-release betamethasone acetate, betamethasone phosphate and the high materno-fetal betamethasone concentrations it generates are redundant for fetal lung maturation. Objective Using an established sheep model of prematurity and post-natal ventilation of the preterm lamb, we aimed to compare the pharmacodynamic effects of a low-dose treatment with betamethasone acetate only against a standard dose of betamethasone phosphate and betamethasone acetate as recommended by the American College of Obstetricians and Gynaecologists for women at risk of imminent preterm delivery between 24 and 35+6 weeks’ gestation. Methods Ewes carrying a single fetus at 122±1 d gestational age (term=150d) were randomized to receive either: i) maternal intramuscular injections of sterile saline (the Saline Negative Control Group, n=12), ii) two maternal intramuscular injections of 0.25 mg/kg betamethasone phosphate + acetate spaced by 24h (the Beta-P+Ac Group, n=12); or iii) two maternal intramuscular injections of 0.125 mg/kg betamethasone acetate spaced by 24h (the Beta-Ac Group, n=11). Fetuses were surgically delivered 48h after treatment initiation and ventilated for 30 minutes to determine functional lung maturation. Fetuses were euthanized after ventilation and lung were collected for analysis using quantitative polymerase chain reaction and western blot assays. Fetal plasma ACTH levels were measured in the cord blood samples taken at delivery. Results Preterm lambs were defined as either ACS treatment

Objective Antenatal corticosteroids (ACS) are the standard of care for maturing the fetal lung and improving outcomes for preterm infants. ACS dosing remains un-optimized, and there is little understanding of how different treatment to delivery intervals may affect treatment efficacy. The durability of a lung maturational response is important because the majority of women treated with ACS do not deliver within the widely accepted 1-7 day window of treatment efficacy. We used a sheep model to test duration of fetal exposures for efficacy at delivery intervals from 1 to 10 days. Methods For infusion studies, ewes with single fetuses were randomised to receive an intravenous bolus and maintenance infusion of betamethasone phosphate to target 1-4ng/mL fetal plasma betamethasone for 36 hours, with delivery at either 2, 4 or 7 days-post treatment or sterile saline as control. Animals receiving the clinical treatment were randomised to receive either:i) a single injection of 0.25mg/kg with a 1:1 mixture of betamethasone phosphate + betamethasone acetate with delivery at either 1 or 7 days post treatment; or ii) two treatments of 0.25 mg/kg betamethasone phosphate + betamethasone acetate spaced at 24 hours (giving approximately 48 hours of fetal steroid exposure) with delivery at 2, 5, 7 or 10 days post-treatment. Negative control animals were treated with saline. All lambs were delivered at 121±3 days gestational age and ventilated for 30 minutes to assess lung function. Results Preterm lambs delivered at 1 or 2 days post-ACS treatment had significant improvements in lung maturation for both intravenous and single dose intramuscular treatments. After 2 days the efficacy of 36 hour betamethasone phosphate infusions was lost. The single dose of 1:1 betamethasone phosphate + betamethasone acetate also was ineffective at 7 days. In contrast, animals treated with two doses had significant improvements in lung maturation at 2, 5 and 7 days, with treatment efficacy reduced by 10