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.

OBJECTIVE: Extremely preterm infants have low Nuclear Receptor (NR) expression in their developing hepatobiliary systems, as they rely on the placenta and maternal liver for compensation. NRs play a crucial role in detoxification and the elimination of both endogenous and xenobiotic substances by regulating key genes encoding specific proteins. In this study, we utilized an Artificial Placenta Therapy (APT) platform to examine the liver tissue expression of NRs of extremely preterm ovine fetuses. This fetal model, resembling a "knockout placenta," lacks placental and maternal support, while maintaining a healthy extrauterine survival. METHODS: Six ovine fetuses at 95 ± 1 d gestational age (GA; term = ∼150 d)/∼600 g delivery weight were maintained on an APT platform for a period of 120 h (APT Group). Six age-matched, in utero control fetuses were delivered at 99-100 d GA (Control Group). Fetal liver tissue samples and blood samples were collected at delivery from both groups and assessed mRNA expression of NRs and target transporters involved in the hepatobiliary transport system using quantitative PCR. Data were tested for group differences with ANOVA (p < .05 deemed significant). RESULTS: mRNA expression of NRs was identified in both the placenta and the extremely preterm ovine fetal liver. The expression of HNF4α, LRH1, LXR, ESR1, PXR, CAR, and PPARα/γ were significantly elevated in the liver of the APT Group compared to the Control Group. Moreover, target transporters NTCP, OATP1B3, BSEP, and MRP4 were upregulated, whereas MRP2 and MRP3 were unchanged. Although there was no evidence of liver necrosis or apoptotic changes histologically, there was an impact in the fetal liver of the ATP group at the tissue level with a significant increase in TNFα mRNA, a cytokine involved in liver inflammation, and blood elevation of transaminases. CONCLUSION: A number of NRs in the fetal liver were significantly upregulated after loss of placental-maternal support. However, the expression of target transporter genes appeared to be insufficient to compensate role of the placenta and maternal liver and avoid fetal liver damage, potentially due to insufficient excretion of organic anions.

BACKGROUND: Antenatal steroid therapy for fetal lung maturation is routinely administered to women at risk of preterm delivery. There is strong evidence to demonstrate benefit from antenatal steroids in terms of survival and respiratory disease, notably in infants delivered at or below 32 weeks' gestation. However, dosing remains unoptimized and lung benefits are highly variable. Current treatment regimens generate high-concentration, pulsatile fetal steroid exposures now associated with increased risk of childhood neurodevelopmental diseases. We hypothesized that damage-associated changes in the fetal hippocampal transcriptome would be independent of preterm lung function. METHODS: Date-mated ewes carrying a single fetus at 122 ± 2dGA (term = 150dGA) were randomized into 4 groups: (i) Saline Control Group, 4×2ml maternal saline intramuscular(IM) injections at 12hr intervals (n = 11); or (ii) Dex High Group, 2×12mg maternal IM dexamethasone phosphate injections at 12hr intervals followed by 2×2ml IM saline injections at 12hr intervals (n = 12; representing a clinical regimen used in Singapore); or (iii) Dex Low Group, 4×1.5mg maternal IM dexamethasone phosphate injections 12hr intervals (n = 12); or (iv) Beta-Acetate Group, 1×0.125mg/kg maternal IM betamethasone acetate injection followed by 3×2ml IM sterile normal saline injections 12hr intervals (n = 8). Lambs were surgically delivered 48hr after first maternal injection at 122-125dGA, ventilated for 30min to establish lung function, and euthanised for necropsy and tissue collection. RESULTS: Preterm lambs from the Dex Low and Beta-Acetate Groups had statistically and biologically significant lung function improvements (measured by gas exchange, lung compliance). Compared to the Saline Control Group, hippocampal transcriptomic data identified 879 differentially significant expressed genes (at least 1.5-fold change and FDR < 5%) in the steroid-treated groups. Pulsatile dexamethasone-only exposed groups (Dex High and Dex Low) had three common positively enriched differentially expressed pathways related in part to neurodegeneration ("Prion Disease", "Alzheimer's Disease", "Arachidonic Acid metabolism"). Adverse changes were independent of respiratory function during ventilation. CONCLUSIONS: Our data suggests that exposure to antenatal steroid therapy is an independent cause of damage- associated transcriptomic changes in the brain of preterm, fetal sheep. These data highlight an urgent need for careful reconsideration and balancing of how antenatal steroids are used, both for patient selection and dosing regimens.

BACKGROUND: A combination of budesonide and surfactant decreases the rates of BPD in infants and lung injury in preterm sheep. Whether this combination will show benefit in the setting of chorioamnionitis and antenatal steroids is not known. METHODS: Ewes at 123 ± 1 day gestational age received intra-amniotic (IA) injections of 10 mg LPS before being randomized to receive either 0.25 mg/kg maternal betamethasone phosphate and acetate or saline by intramuscular (IM) injection at 48 and 24 h prior to delivery at 125 ± 1 day. Lambs (N = 6-9/group) underwent intentionally injurious ventilation for 15 min, then lambs received surfactant mixed with either: (1) saline; or (2) Budesonide 0.25 mg/kg and were ventilated for 4 h. RESULTS: Compared with LPS-exposed animals that received no IM steroid treatment, betamethasone exposed fetuses had improved hemodynamic stability, lung compliance, and ventilation efficiency. The addition of budesonide to surfactant further improved markers of injury and pro-inflammatory cytokine mRNA in both betamethasone IM or no IM lambs exposed to LPS IA. Antenatal betamethasone and IA LPS exposures decreased budesonide levels in the fetal lung and plasma. CONCLUSION: Antenatal betamethasone stabilizes physiologic parameters in LPS treated lambs. Budesonide mixed with surfactant further decreases injury and improves respiratory physiology in betamethasone treated animals. IMPACT: Antenatal betamethasone improved lung and systemic physiology in the setting of intra-amniotic LPS. The addition of budesonide to the surfactant further improved lung function. Budesonide levels in the plasma and lung were lower in lambs exposed to either LPS or LPS and Betamethasone animals, and these findings were not explained by increased esterification in the lungs. The combination of antenatal steroids and budesonide with surfactant had the lowest markers of pro-inflammatory cytokines in the lung of LPS exposed animals.

Background: Antenatal steroid therapy is standard of care for women at imminent risk of preterm delivery. Current dosing regimens employ supra-pharmacological doses to achieve extended fetal steroid exposures. Objective: We aimed to determine the lowest fetal plasma betamethasone concentration sufficient to achieve functional preterm lung maturation. Study design: Ewes with singles fetuses underwent surgery to install a fetal jugular catheter. Adopting a step-wise design, ewes were randomised 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 levels of either: i) 2 ng/ml (2 ng/ml Positive Control Group, n=9); ii) 1 ng/ml, (1 ng/ml Group, n=10); iii) 0.5 ng/ml (0.5 ng/ml Group, n=10); or iv) 0.25 ng/ml Group (0.25 ng/ml Group, n=10). Fetuses were infused for 48 hours, 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. Results: 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 favour of the 0.25 ng/ml Group. Treatment efficacy was progressively lost at plasma betamethasone concentrations lower than 2 ng/ml. Conclusion: 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.

Introduction: Artificial placenta therapy (APT) is an experimental life support system to improve outcomes for extremely preterm infants (EPI) less than 1,000 g by obviating the need for pulmonary gas exchange. There are presently no long-term survival data for EPI supported with APT. To address this, we aimed to maintain 95d-GA (GA; term-150d) sheep fetuses for up to 2 weeks using our APT system. Methods: Pregnant ewes (n = 6) carrying singleton fetuses underwent surgical delivery at 95d GA. Fetuses were adapted to APT and maintained for up to 2 weeks with constant monitoring of key physiological parameters and extensive time-course blood and urine sampling, and ultrasound assessments. Six age-matched in-utero fetuses served as controls. Data were tested for group differences with ANOVA. Results: Six APT Group fetuses (100%) were adapted to APT successfully. The mean BW at the initiation of APT was 656 ± 42 g. Mean survival was 250 ± 72 h (Max 336 h) with systemic circulation and key physiological parameters maintained mostly within normal ranges. APT fetuses had active movements and urine output constantly exceeded infusion volume over the experiment. At delivery, there were no differences in BW (with edema in three APT group animals), brain weight, or femur length between APT and in-utero Control animals. Organ weights and humerus lengths were significantly reduced in the APT group (p &amp;lt; 0.05). Albumin, IGF-1, and phosphorus were significantly decreased in the APT group (p &amp;lt; 0.05). No cases of positive blood culture were detected. Conclusion: We report the longest use of APT to maintain extremely preterm fetuses to date. Fetal systemic circulation was maintained without infection, but growth was abnormal. This achievement suggests a need to focus not only on cardiovascular stability and health but also on the optimization of fetal growth and organ development. This new challenge will need to be overcome prior to the clinical translation of this technology.

CONTEXT: Intrauterine inflammation, a representative stressor for the fetus, has been shown to alter the hypothalamus-pituitary-adrenal (HPA) axis reactivity in preterm fetuses and increase postnatal cortisol production. However, the mechanism of this alteration has not yet been elucidated. OBJECTIVE: We aimed to clarify the effects of endotoxin-induced intrauterine inflammation on the HPA axis of periviable sheep fetuses. METHODS: Fetal sheep (0.63 term) were divided into 2 groups: (1) the endotoxin group, in which the endotoxin was injected into the amniotic fluid; and (2) the control group, in which the saline solution was injected instead. A corticotropin-releasing hormone (CRH) challenge test was performed on the third day after injection to evaluate the cortisol-producing capacity of each group. Gene expression levels in the fetal adrenal glands of each group were analyzed by RNA-seq. RESULTS: The cortisol levels were significantly higher in the endotoxin group than in the control group after CRH challenge (P = .02). There were no significant differences in the responsiveness of adrenocorticotropin and cortisone between the 2 groups. Gene expression levels of the following enzymes involved in cortisol synthesis were significantly elevated in the endotoxin group: cytochrome P450 family (CYP) 11 subfamily A member 1 (log2FC 1.75), CYP 17 subfamily A member 1 (log2FC 3.41), 3β-hydroxysteroid dehydrogenase type I (log2FC 1.13), steroidogenic acute regulatory protein (log2FC 1.09), and CYP 21 (log2FC 0.89). CONCLUSION: Periviable fetuses exposed to inflammation in utero have altered the responsiveness of the HPA axis with increased expression of enzymes involved in cortisol synthesis in the adrenal gland.

Despite widespread use, dosing regimens for antenatal corticosteroid (ACS) therapy are poorly unoptimized. ACS therapy exerts a programming effect on fetal development, which may be associated with an increased risk of cardiovascular disease. Having demonstrated that low-dose steroid therapy is an efficacious means of maturing the preterm lung, we hypothesized that a low-dose steroid exposure would exert fewer adverse functional and transcriptional changes on the fetal heart. We tested this hypothesis using low-dose steroid therapy (10 mg delivered to the ewe over 36 h via constant infusion) and compared cardiac effects with those of a higher dose treatment (30 mg delivered to the ewe over 24 h by intramuscular injection; simulating currently employed clinical ACS regimens). Fetal cardiac function was assessed by ultrasound on the day of ACS treatment initiation. Transcriptomic analyses were performed on fetal myocardial tissue. Relative to saline control, fetuses in the higher-dose clinical treatment group had significantly lower ratios between early diastolic ventricular filling and ventricular filling during atrial systole, and showed the differential expression of myocardial hypertrophy-associated transcripts including βMHC, GADD45γ, and PPARγ. The long-term implications of these changes remain unstudied. Irrespective, optimizing ACS dosing regimens to maximize respiratory benefit while minimizing adverse effects on key organ systems, such as the heart, offers a means of improving the acute and long-term outcomes associated with this important obstetric therapy.

INTRODUCTION: Lysophosphatidylcholine acyltransferase 1 (LPCAT1) is important for saturated phosphatidylcholine (Sat-PC) production in the lung. Sat-PC is a critical component of pulmonary surfactant, which maintains low alveolar surface tension, facilitating respiration. Previous studies have reported an association between maternal and fetal LPCAT1 levels and neonatal lung function. Using a sheep model of pregnancy, we investigated a potential correlation between glucocorticoid-induced lung maturation and LPCAT1 mRNA and/or protein levels in the fetal lung, the placenta, the fetal plasma, and the maternal plasma. METHODS: Eighty seven single pregnant ewes received maternal intramuscular injections of betamethasone. A sub-group of five animals had both maternal and fetal catheters installed to allow for sequential sampling from both plasma compartments. Lambs were surgically delivered under terminal anaesthesia between 2 and 8 days after initial ANS treatment, at a gestational age of 121-123 days. Lambs were ventilated for 30 min to determine functional lung maturation before being euthanized for necropsy and sample collection. Fetal lung, placenta, and fetal and maternal plasma samples were used to analyse LPCAT1 gene expression and protein levels. RESULTS: The expression of LPCAT1 mRNA in the fetal lung was significantly corelated to Sat-PC levels at 8 days (R2 = 0.23, p < 0.001) and lung maturation status overall (gas exchange efficiency as determined by measurements of lamb PaCO2 during ventilation, R2 = 0.20, p < 0.001). Similarly, fetal lung LPCAT1 mRNA was also significantly correlated with the individual durability of ANS effects on fetal lung maturation (R2 = 0.20, p < 0.001). Although ANS therapy altered LPCAT1 mRNA expression in the placenta, observed changes were independent of fetal lung maturation outcomes. Neither maternal nor fetal plasma LPCAT1 levels were changed by ANS therapy over the period, including in analysis of serial maternal and fetal samples from chronically catheterised animals. DISCUSSION: LPCAT1 expression in the fetal lung was associated with the durability of glucocorticoid effects on fetal lung maturation. However, LPCAT1 expression in the placenta, the fetal plasma, and the maternal plasma was neither associated with, nor predictive of fetal lung maturation after glucocorticoid treatment in a sheep model of pregnancy.

Thoracic empyema usually occurs as a complication of bacterial pneumonia, but in rare cases, it is caused by hematogenous dissemination secondary to nonpulmonary diseases. Congenital chylothorax or chylothorax in children is associated with maldevelopment of the lymphatic system, nonimmune hydrops fetalis, several syndromes including Down syndrome, Noonan syndrome, or Turner syndrome, a complication of thoracic surgery, right heart failure with high central venous pressure, or tumors. There are very few reports of empyema associated with preexisting chylothorax. In the present study, we describe a rare case of thoracic empyema associated with congenital chylothorax and supravalvular pulmonary stenosis associated with clinically diagnosed Noonan syndrome. It is necessary to closely monitor patients with chylothorax because they are at risk of developing severe lung infections, such as pleural empyema or lung abscesses.

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 administration, the average MCP-1 concentrations in the AF were significantly lower in the LPS + rytvela Group relative to in the LPS Group. In delivery samples, the expression of IL-1β in fetal skin was significantly lower in the LPS + rytvela Group compared to the LPS Group. CONCLUSION: A single dose of rytvela was associated with partial, modest inhibition in the expression of a panel of cytokines/chemokines in fetal tissues undergoing an active inflammatory response.

BACKGROUND: Administration of antenatal steroids is standard of care for women assessed to be at imminent risk of preterm delivery. There is a marked variation in antenatal steroid dosing strategy, selection for treatment criteria, and agent choice worldwide. This, combined with very limited optimization of antenatal steroid use per se, means that treatment efficacy is highly variable, and the rate of respiratory distress syndrome is decreased to perhaps as low as 40%. In some cases, antenatal steroid use is associated with limited benefit and potential harm. OBJECTIVE: We hypothesized that individual differences in maternofetal steroid exposure would contribute to observed variability in antenatal steroid treatment efficacy. Using a chronically catheterized sheep model of pregnancy, we aimed to explore the relationship between maternofetal steroid exposure and antenatal steroid treatment efficacy as determined by functional lung maturation in preterm lambs undergoing ventilation. STUDY DESIGN: Ewes carrying a single fetus underwent surgery to catheterize a fetal and maternal jugular vein at 119 days' gestation. Animals recovered for 24 hours before being randomized to either (1) a single maternal intramuscular injection of 2 mL saline (negative control group, n=10) or (2) a single maternal intramuscular injection of 0.25 mg/kg betamethasone phosphate plus acetate (antenatal steroid group, n=20). Serial maternal and fetal plasma samples were collected from each animal after 48 hours before fetuses were delivered and ventilated for 30 minutes. Total and free plasma betamethasone concentration was measured by mass spectrometry. Fetal lung tissue was collected for analysis using quantitative polymerase chain reaction. RESULTS: One animal from the control group and one animal from the antenatal steroid group did not complete their treatment protocol and were removed from analyses. Animals in the antenatal steroid group were divided into a responder subgroup (n=12/19) and a nonresponder subgroup (n=7/19) using a cutoff of partial pressure of arterial CO2 at 30-minute ventilation within 2 standard deviations of the mean value from saline-treated negative control group animals. Although antenatal steroid improved fetal lung maturation in the undivided antenatal steroid group and in the responder subgroup both physiologically (blood gas- and ventilation-related data) and biochemically (messenger ribonucleic acid expression related to fetal lung maturation), these values did not improve relative to saline-treated control group animals in the antenatal steroid nonresponder subgroup. No differences in betamethasone distribution, clearance, or protein binding were identified between the antenatal steroid responder and nonresponder subgroups. CONCLUSION: This study correlated individual maternofetal steroid exposures with preterm lung maturation as determined by pulmonary ventilation. Herein, approximately 40% of preterm lambs exposed to antenatal steroids had lung maturation that was not significantly different to saline-treated control group animals. These nonresponsive animals received maternal and fetal betamethasone exposures identical to animals that had a significant improvement in functional lung maturation. These data suggest that the efficacy of antenatal steroid therapy is not solely determined by maternofetal drug levels and that individual fetal or maternal factors may play a role in determining treatment outcomes in response to glucocorticoid signaling.

[INTRODUCTION]: Ex-vivo uterine environment (EVE) therapy is an experimental intensive care strategy for extremely preterm infants born between 21 and 24 weeks of gestation. Gas exchange is performed by membranous oxygenators connected by catheters to the umbilical vessels. The fetus is submerged in a bath of synthetic amniotic fluid. The lungs remain fluid-filled and pulmonary respiration does not occur. Intrauterine inflammation is strongly associated with extremely early preterm birth and fetal injury. Presently, there are no data of which we are aware to show that artificial placenta-based systems can be used to support extremely preterm fetuses compromised by exposure to intrauterine inflammation. [OBJECTIVES]: To evaluate the ability of our EVE therapy platform to support extremely preterm ovine fetuses (95 d gestational age; approximately equivalent to 24 weeks of human gestation) exposed to intrauterine inflammation for a period of 120 hours, the following primary endpoints were chosen: i) maintenance of key physiological variables within normal ranges; ii) absence of infection and inflammation; iii) absence of brain injury; and iv) gross fetal growth and cardiovascular function matching that of age-matched in utero controls. [STUDY DESIGN]: Ten ewes with singleton pregnancies were each given a single intraamniotic injection of 10 mg E.coli lipopolysaccharides (LPS) under ultrasound guidance 48h before undergoing surgical delivery for adaptation to EVE therapy at 95d gestation (term=150d). Fetuses were adapted to EVE therapy and maintained for 120h with constant monitoring of key vital parameters (EVE Group) before being euthanised at 100d equivalent gestational age. Umbilical artery blood samples were regularly collected to assess blood gas data, differential counts, biochemical parameters, inflammatory markers and microbial load to exclude infection. Ultrasound was conducted at 48 h after intraamniotic LPS (before surgery) to confirm fetal viability and at the conclusion of the experiments (before euthanasia) to evaluate cardiac function. Brain injury was evaluated by gross anatomical and histopathological investigations. Eight singleton pregnant control animals were similarly exposed to intraamniotic LPS at 93d gestation and were euthanized at 100 d gestation to allow comparative post-mortem analyses (Control Group). Bio-banked samples from age-matched saline-treated animals served as an additional comparison group. Successful instillation of LPS into the amniotic fluid exposure was confirmed by amniotic fluid analysis at the time of administration, and by analyzing cytokine levels in fetal plasma and amniotic fluid. Data were tested for mean differences with ANOVA. [RESULTS]: Six out of eight LPS Control Group (75%) and eight out of ten EVE Group fetuses (80%) successfully completed their protocols. Six of eight EVE Group fetuses required dexamethasone phosphate treatment to manage profound refractory hypotension. Weight and crown rump length was reduced in EVE Group fetuses at euthanasia compared to LPS Control Group fetuses (p<0.05). There were no biologically significant differences in cardiac ultrasound measurement, differential leucocyte counts (p>0.05), plasma tumour necrosis factor α (TNF-α), monocyte chemoattractant protein-1 (MCP-1) concentrations (p>0.05), or liver function tests between groups. Daily blood cultures were negative for aerobic and anaerobic growth in all EVE Group animals. No cases of intraventricular haemorrhage were observed. White matter injury was identified in three of six LPS Control Group fetuses and three of eight EVE Group fetuses. [CONCLUSIONS]: We report the use of an artificial placenta-based system to support extremely preterm lambs compromised by exposure to intrauterine inflammation. Our data highlight key challenges (refractory hypotension, growth restriction and white matter injury) to be overcome in the development and use of artificial placenta technology for extremely early preterm infants. As such challenges appear largely absent from studies based on healthy pregnancies, additional experiments of this nature using clinically relevant model systems are essential for further development of this technology and its eventual clinical application.

BACKGROUND: Arginine vasopressin (AVP) infusion has been shown to be a useful strategy for the management of systemic perfusion failure in premature infants. Our objective was to determine the characteristics of the blood flow redistribution induced by AVP infusion in premature fetal sheep. METHODS: Nine sheep fetuses at 99 to 113 days of gestation were continuously infused with AVP. Measurement of blood flow to individual fetal organs was performed using a colored-microsphere technique, with measurements performed at 30 minutes before and 90 minutes after the initiation of AVP infusions. RESULTS: The AVP infusion significantly increased blood flow to the medulla oblongata (p < 0.05), and significantly decreased flow to the adrenal glands (from 492.0 ± 239.6 to 364.9 ± 143.3 ml/min/100 g, p < 0.05) and heart (from 592.6 ± 184.5 to 435.6 ± 137.4 ml/min/100 g, p < 0.05). The infusion significantly increased the vascular resistance in adrenal glands, kidneys, ileum, colon, heart and cerebellum. In the brain, except for cerebellum, no significant increase in resistance was identified. CONCLUSION: There was no significant response to AVP infusion in cerebral blood flow in mid-gestation fetal sheep. Our observations suggest that, under AVP stimulation, the blood flow to the adrenal glands and myocardium might be decreased due to an increase of the vascular resistance.