Systematic Route to Subcritical Dynamo Branches.

We demonstrate that the nonlinear optimization of a finite-amplitude disturbance over a freely evolving and possibly even turbulent flow, can successfully identify subcritical dynamo branches as well as the structure and amplitude of their critical perturbations. As this approach does not require prior knowledge of the magnetic field amplification mechanisms, it opens a new avenue for systematically probing subcritical dynamo flows.

Feeding growth restricted premature neonates: a challenging perspective.

Nutrition in the postnatal period is essential to achieve optimal growth and maintain biochemical normality. Feeding growth-restricted premature neonates remains a big challenge for pediatricians and neonatologists. The choice of milk is one of the biggest challenges. Breast milk is recommended, although feeding with preterm formulas can ensure a more consistent delivery of optimal levels of nutrients. The timing of introduction of feeds and the rate of advancement of those feeds in preterm infants are both topics of significant controversy. Early feeding is advantageous because it improves the functional adaptation of the gastrointestinal tract and reduces the duration of total parenteral nutrition. A faster rate of advancement will also reduce the duration of need for parenteral nutrition. Despite this, enteral feeding is often delayed and is often slowly increased in high-risk infants because of a possible increased risk of necrotizing enterocolitis (NEC). Growth-restricted neonates are at increased risk of developing NEC due to a combination of antenatal and postnatal disturbances in gut perfusion. If enteral feeding is introduced earlier and advanced more quickly, this may lead to increased risk of NEC, but slower feeds extend the duration of parenteral nutrition and its risks and may have adverse consequences for survival, growth, and development. Premature infants pose a significant nutritional challenge. Overall, we would suggest the preferential use of human breast milk, early minimal enteral feeds, and standardized feeding protocols with cautious advancements of feeds to facilitate gastrointestinal adaptation and reduce the risk of NEC, however further research is needed.

Superior vena cava flow and intraventricular haemorrhage in extremely preterm infants.

OBJECTIVE: To evaluate the relationship between superior vena cava flow (SVCF) measurements within the first 24 h of life, and development of intraventricular haemorrhage (IVH) in extremely preterm infants. STUDY DESIGN: Single centre retrospective cohort study of 108 preterm infants born less than 28 weeks' gestation. Main outcome measure was degree of IVH at day 7 postnatal age. RESULTS: The mean GA of the study group was 25.4 weeks. Mean SVCF was lower (75 ml/kg/min) in infants later diagnosed with IVH (n = 46) compared to infants, who did not develop IVH (87.7 ml/kg/min, p = 0.055). PDA diameter was inversely associated with SVCF (p = 0.024) and reversal of flow in the descending aorta (p = 0.001). Sensitivity analysis did not confirm an independent association of SVCF with development of IVH [OR 0.990 (0.978-1.002), p = 0.115]. CONCLUSION: Our study describes early SVCF in extremely preterm infants is associated with the extent of ductal shunting, but insensitive in predicting IVH.

Feeding infants below 29 weeks' gestation with abnormal antenatal Doppler: analysis from a randomised trial.

OBJECTIVE: To describe feeding and gastrointestinal outcomes in growth-restricted infants <29 weeks' gestation and to determine the rate of feed advancement which they tolerate. DESIGN: Analysis of prospectively collected data from a randomised feeding trial, the Abnormal Doppler Enteral Prescription Trial (ADEPT). SETTING: 54 neonatal units in the UK and Ireland. PARTICIPANTS: 404 preterm, growth-restricted infants with abnormal antenatal Doppler studies from ADEPT. 83 infants <29 weeks and 312 infants ≥ 29 weeks' gestation were included in this analysis. INTERVENTIONS: In ADEPT, infants were randomised to start milk 'early' on day 2 after birth, or 'late' on day 6. Subsequent feed advancement followed a regimen, which should have achieved full feeds by day 16 in the early and day 20 in the late group. MAIN OUTCOME MEASURES: Full feeds were achieved later in infants <29 weeks; median age 28 days {IQR 22-40} compared with 19 days {IQR 17-23} in infants ≥ 29 weeks (HR 0.35, 95% CI 0.3 to 0.5). The incidence of necrotising enterocolitis was also higher in this group; 32/83 (39%) compared to 32/312 (10%) in those ≥ 29 weeks (RR 3.7, 95% CI 2.4 to 5.7). Infants <29 weeks tolerated very little milk for the first 10 days of life and reached full feeds 9 days later than predicted from the trial regimen. CONCLUSIONS: Growth-restricted infants born <29 weeks' gestation with abnormal antenatal Doppler failed to tolerate even the careful feeding regimen of ADEPT. A slower advancement of feeds may be required for these infants. TRIAL REGISTRATION NUMBER: ISRCTN87351483.

Fetal Limb Ischaemia in Twin-to-Twin Transfusion Syndrome.

Objective. To describe the rare association between prenatal vascular limb occlusion and twin-to-twin transfusion syndrome. The Case. A woman with severe twin-to-twin transfusion syndrome was treated with fetoscopic laser ablation at 19-week gestation. At 27 weeks, the twins were delivered by an emergency caesarean section. The right arm of twin 1, the recipient twin, was noted to be "ischaemic" and was later amputated. Conclusion. This case is unusual in that it affected the upper limb and there was no evidence of polycythaemia, which is a suggested pathological mechanism. It was initially thought that the limb damage was due to the laser ablation, but after discussion with the fetal medicine team vascular limb occlusion in association with twin-to-twin transfusion syndrome was considered. Limb ischaemia is a serious complication of twin-to-twin transfusion syndrome and is unrelated to any form of fetal therapy. Implications. Neonatologists and paediatricians need to be aware of this association as it has medicolegal implications and parents should be counselled as to the possible, albeit rare, occurrence, especially when twin-to-twin transfusion syndrome is of advanced stage at presentation.

Early or delayed enteral feeding for preterm growth-restricted infants: a randomized trial.

BACKGROUND: Growth-restricted preterm infants are at increased risk of developing necrotizing enterocolitis (NEC) and initiation of enteral feeding is frequently delayed. There is no evidence that this delay is beneficial and it might further compromise nutrition and growth. METHODS: Infants with gestation below 35 weeks, birth weight below the 10th centile, and abnormal antenatal umbilical artery Doppler waveforms were randomly allocated to commence enteral feeds "early," on day 2 after birth, or "late," on day 6. Gradual increase in feeds was guided by a "feeding prescription" with rate of increase the same for both groups. Primary outcomes were time to achieve full enteral feeding sustained for 72 hours and NEC. RESULTS: Four hundred four infants were randomly assigned from 54 hospitals in the United Kingdom and Ireland (202 to each group). Median gestation was 31 weeks. Full, sustained, enteral feeding was achieved at an earlier age in the early group: median age was 18 days compared with 21 days (hazard ratio: 1.36 [95% confidence interval: 1.11-1.67]). There was no evidence of a difference in the incidence of NEC: 18% in the early group and 15% in the late group (relative risk: 1.2 [95% confidence interval: 0.77-1.87]). Early feeding resulted in shorter duration of parenteral nutrition and high-dependency care, lower incidence of cholestatic jaundice, and improved SD score for weight at discharge. CONCLUSIONS: Early introduction of enteral feeds in growth-restricted preterm infants results in earlier achievement of full enteral feeding and does not appear to increase the risk of NEC.

ADEPT - Abnormal Doppler Enteral Prescription Trial.

BACKGROUND: Pregnancies complicated by abnormal umbilical artery Doppler blood flow patterns often result in the baby being born both preterm and growth-restricted. These babies are at high risk of milk intolerance and necrotising enterocolitis, as well as post-natal growth failure, and there is no clinical consensus about how best to feed them. Policies of both early milk feeding and late milk feeding are widely used. This randomised controlled trial aims to determine whether a policy of early initiation of milk feeds is beneficial compared with late initiation. Optimising neonatal feeding for this group of babies may have long-term health implications and if either of these policies is shown to be beneficial it can be immediately adopted into clinical practice. METHODS AND DESIGN: Babies with gestational age below 35 weeks, and with birth weight below 10th centile for gestational age, will be randomly allocated to an "early" or "late" enteral feeding regimen, commencing milk feeds on day 2 and day 6 after birth, respectively. Feeds will be gradually increased over 9-13 days (depending on gestational age) using a schedule derived from those used in hospitals in the Eastern and South Western Regions of England, based on surveys of feeding practice. Primary outcome measures are time to establish full enteral feeding and necrotising enterocolitis; secondary outcomes include sepsis and growth. The target sample size is 400 babies. This sample size is large enough to detect a clinically meaningful difference of 3 days in time to establish full enteral feeds between the two feeding policies, with 90% power and a 5% 2-sided significance level. Initial recruitment period was 24 months, subsequently extended to 38 months. DISCUSSION: There is limited evidence from randomised controlled trials on which to base decisions regarding feeding policy in high risk preterm infants. This multicentre trial will help to guide clinical practice and may also provide pointers for future research. TRIAL REGISTRATION: Current Controlled Trials ISRCTN: 87351483.