Body temperature, heart rate and long-term outcome of cooled infants: an observational study.

BACKGROUND: Therapeutic hypothermia is a standard of care for neonatal encephalopathy; however, approximately one in two newborn infants fails to respond to this treatment. Recent studies have suggested potential relationships between body temperature, heart rate and the outcome of cooled infants. METHODS: The clinical data of 756 infants registered to the Baby Cooling Registry of Japan between January 2012 and December 2016 were analysed to assess the relationship between body temperature, heart rate and adverse outcomes (death or severe impairment at 18 months corrected age). RESULTS: A lower body temperature at admission was associated with adverse outcomes in the univariate analysis (P < 0.001), the significance of which was lost when adjusted for the severity of encephalopathy and other covariates. A higher body temperature during cooling and higher heart rate before and during cooling were associated with adverse outcomes in both univariate (all P < 0.001) and multivariate (P = 0.012, P < 0.001 and P < 0.001, respectively) analyses. CONCLUSIONS: Severe hypoxia-ischaemia might be a common causative of faster heart rates before and during cooling and low body temperature before cooling, whereas causal relationships between slightly higher temperatures during cooling and adverse outcomes need to be elucidated in future studies. IMPACT: In a large cohort of encephalopathic newborn infants, dual roles of body temperature to the outcome were shown; adverse outcomes were associated with a lower body temperature at admission and higher body temperature during cooling. A higher heart rate before and during cooling were associated with adverse outcomes. Severe hypoxia-ischaemia might be a common causative of faster heart rates before and during cooling and low body temperature before cooling. The exact mechanism underlying the relationship between slightly higher body temperature during cooling and adverse outcomes remains unknown, which needs to be elucidated in future studies.

Validation of actigraphy in hospitalised newborn infants using video polysomnography.

Actigraphy has been established as a reliable sleep assessment tool in adults; however, its utility in newborns remains unknown. Validation of actigraphy in newborns may provide a significant insight into the physiological and pathological acquisition process of mature diurnal sleep patterns and subsequent morbidities in both newborns and their mothers. Thus, the present study aimed to evaluate the accuracy of sleep-wake detection by overnight actigraphy in a cohort of newborns. Simultaneous recording of polysomnography and actigraphy data was performed in 40 newborns admitted to a tertiary neonatal intensive care unit (NICU). A mixed-effects logistic regression model to explain the sleep state identified by polysomnography was employed using the actigraphic activity score as a fixed independent variable and the individual newborn's identity as a random effect. To evaluate the usefulness of the actigraphic activity score as a surrogate marker of sleep, a receiver operating characteristic (ROC) curve analysis was performed using the variables that were used in the mixed-effects logistic regression model, and the area under the curve (AUC) was assessed. The results showed that polysomnography-determined sleep epochs were associated with a smaller activity index on actigraphy (odds ratio per 10 activity indices increase 0.81, 95% confidence interval [CI] 0.79-0.84). The AUC for the ROC curve was 0.87 (95% CI 0.87-0.88, range 0.54-0.99). An activity score of 124 showed the maximum overall accuracy (90.2%, 95% CI 87.7-92.1). Our present study suggests that sleep-wake states of NICU-hospitalised newborns can be precisely determined using actigraphy on the ankle.

Revisions of clinical protocols using the Plan Do Check Act cycle improved outcomes of extremely preterm infants at 2 years.

AIM: Clinical quality improvement is often cumbersome due to established protocols. We aimed to investigate whether outcomes of preterm infants improve with protocol revisions using iteration cycles. METHODS: Preterm infants born <28 weeks gestation between January 2006 and December 2015 were retrospectively analysed. Protocols were revised using Plan Do Check Act cycle. Death and serious adverse events at term were reviewed in six-monthly quality improvement meetings. Adverse outcome of death or motor/sensory impairments at two years was compared before and after two major protocol changes, which were implemented in January 2008 and January 2012. RESULTS: Based on the appraisal for period 2006-2007, strategies for surfactant, narcotics, parenteral nutrition, respiratory gas humidity and prophylactic indomethacin and antibiotics were changed for period 2008-2011. For period 2012-2015, stabilisation of infants was accelerated via very early catheterisation. Of 162 infants (84 males, 25.5 ± 1.5 weeks gestation) within the whole cohort, 63 developed adverse outcomes, which were fewer for periods 2008-2011 (p = 0.013) and 2012-2015 (p = 0.035) compared with period 2006-2007 (adjusted for gestational age, Apgar scores and sex). CONCLUSION: Careful bottom-up revisions of protocols using iteration cycles, accounting for local settings, successfully improved the outcomes of preterm infants.

Body Size, Cerebral Blood Flow, Ambient Temperature, and Relative Brain Temperatures in Newborn Infants under Incubator Care.

Subtle changes in body temperature affect the outcomes of ill newborns. However, the temperature profile of neonatal brains remains largely unknown. In open-cot care, increased cerebral perfusion is correlated with higher superficial brain temperatures. This study investigated the dependence of brain temperature (relative to rectal temperature) on ambient temperature, body size, cerebral perfusion, and metabolism in infants receiving incubator care. Rectal, scalp, and brain temperatures, superior vena cava flow, and brain oxygenation were assessed using echocardiography, thermo-compensatory temperature monitoring, and near-infrared spectroscopy in 60 newborns. These infants had a mean postconceptional age of 36.9 (2.2) weeks and weighed 2348 (609) g at the time of evaluation. The ambient temperature was maintained at 30.0 (1.0) °C. A higher rectal temperature was associated with greater postconceptional age (p = 0.002), body weight (p < 0.001), and head circumference (p < 0.001). Relative scalp, superficial brain, and deep brain temperatures were associated with smaller head circumference (p < 0.001, p = 0.030, and p = 0.015, respectively) and superior vena cava flow (p = 0.002, p = 0.003, and p = 0.003, respectively). In infants receiving incubator care, larger head sizes and increased brain perfusion were associated with lower relative scalp and brain temperatures. When considered alongside previous reports, cerebral perfusion may contribute to maintaining stable cerebral tissue temperature against ambient temperature changes.

Antenatal Growth, Gestational Age, Birth, Enteral Feeding, and Blood Citrulline Levels in Very Low Birth Weight Infants.

Early enteral nutrition using reliable biomarkers of intestinal function must be established to improve neurodevelopmental outcomes in very low birth weight infants (VLBWIs). Serum citrulline levels reflect the intestinal function in adults. To elucidate the relationship among antenatal growth, postnatal enteral nutrition, and blood citrulline levels, a retrospective single-center observational study was conducted on 248 VLBWIs born between April 2014 and March 2021. A mixed effect model and post hoc simple slope analysis were used to estimate the correlations between clinical variables and citrulline levels at Early (day 5.1) and Late (day 24.3) postnatal ages. Greater gestational age, birth weight, and amount of enteral nutrition at the time of blood sampling were associated with lower citrulline levels at the Early postnatal age and higher citrulline levels at the Late postnatal age. Provided that Early citrulline levels predominantly reflect the consequence of antenatal citrulline metabolism, it is suggested that fetal growth and maturation are likely to promote citrulline catabolism in utero and its synthesis after birth. With additional insights into the temporal transition point wherein the maturation-dependent balance of citrulline metabolism shifts from catabolism-dominant to synthesis-dominant, citrulline emerges as a potential biomarker for assessing intestinal function and gastrointestinal disorders.

Methyl-isobutyl amiloride reduces brain Lac/NAA, cell death and microglial activation in a perinatal asphyxia model.

Na⁺/H⁺ exchanger (NHE) blockade attenuates the detrimental consequences of ischaemia and reperfusion in myocardium and brain in adult and neonatal animal studies. Our aim was to use magnetic resonance spectroscopy (MRS) biomarkers and immunohistochemistry to investigate the cerebral effects of the NHE inhibitor, methyl isobutyl amiloride (MIA) given after severe perinatal asphyxia in the piglet. Eighteen male piglets (aged < 24 h) underwent transient global cerebral hypoxia-ischaemia and were randomized to (i) saline placebo; or (ii) 3 mg/kg intravenous MIA administered 10 min post-insult and 8 hourly thereafter. Serial phosphorus-31 (³¹P) and proton (¹H) MRS data were acquired before, during and up to 48 h after hypoxia-ischaemia and metabolite-ratio time-series Area under the Curve (AUC) calculated. At 48 h, histological and immunohistochemical assessments quantified regional tissue injury. MIA decreased thalamic lactate/N-acetylaspartate and lactate/creatine AUCs (both p < 0.05) compared with placebo. Correlating with improved cerebral energy metabolism, transferase mediated biotinylated d-UTP nick end-labelling (TUNEL) positive cell density was reduced in the MIA group in cerebral cortex, thalamus and white matter (all p < 0.05) and caspase 3 immunoreactive cells were reduced in pyriform cortex and caudate nucleus (both p < 0.05). Microglial activation was reduced in pyriform and midtemporal cortex (both p < 0.05). Treatment with MIA starting 10 min after hypoxia-ischaemia was neuroprotective in this perinatal asphyxia model.

Sleep patterns of Japanese preschool children and their parents: implications for co-sleeping.

AIM: The aim of this study was to investigate the direct relationship of sleep schedule and sleep quality variables between healthy preschool children and their parents, focusing on the influence of the difference in bedtime between each other. METHODS: Forty-seven Japanese 5-year-old children and their primary parent were studied. The parents completed questionnaires including the Epworth Sleepiness Scale and Pittsburgh Sleep Quality Index. The children wore an actigraph for one week. RESULTS: Although sleep patterns of children were generally independent of their parents, late sleep end time and bedtime of children were associated with parents' late sleep end time on weekends. For 87% of children and parents who shared a bedroom, sleep quality was negatively affected by a shorter difference in bedtimes between child and parent, but not by co-sleeping. CONCLUSION: Sleep behaviours of parents can influence those of their children. For parents and children who share a bedroom, the timing of bedtime rather than co-sleeping may be a key factor in modulating sleep patterns. Trying to get children asleep and subsequently falling asleep at a similar time may disturb parents' sleep quality, which may subsequently affect that of their children.

Control variables of serum ferritin concentrations in hospitalized newborn infants: an observational study.

Both iron excess and deficiency are deleterious to cellular and organ homeostasis. Serum ferritin levels serve as a biomarker of iron storage; however, their distribution and determinants in sick newborn infants remain unclear. This study aimed to investigate the reference range and independent variables of serum ferritin in hospitalized newborn infants. All newborn infants who were hospitalized at a tertiary neonatal center within 24 h of birth were retrospectively reviewed for the period of April 2015 through March 2017. Serum ferritin levels were assessed using venous blood samples obtained at admission and their independent variables were explored. The study population comprised 368 infants (36.2 ± 2.8 weeks gestation and 2319 ± 623 g at birth), whose median serum ferritin level was 149 µg/L (inter-quartile range: 81-236). The multivariable model used to explain serum ferritin values comprised hemoglobin, lactate dehydrogenase, blood pH, and maternal hypertensive disorders in pregnancy (all p < 0.01, adjusted for sex and birth weight). Serum ferritin values in hospitalized newborn infants were comparable to those previously reported using umbilical cord blood. Our novel findings indicated the association between blood pH, lactate dehydrogenase, and ferritin levels, suggesting the influence of antenatal hypoxia-ischemia and stress to serum ferritin levels.

Sleep architecture in healthy 5-year-old preschool children: associations between sleep schedule and quality variables.

AIM: Although disturbed sleep quality such as night awakenings and difficulties in falling asleep are common symptoms during sleep in preschool children, relationships between sleep quality and sleep schedule are mostly unknown. This study aimed to evaluate the relationships between sleep schedule and quality variables in preschool children. METHODS: Sleep-wake patterns of 48 healthy 5-year-old children were assessed over 7 consecutive days using actigraphy. RESULTS: Children with longer sleep latency had a lower sleep quality, a later bedtime, a later sleep onset time, a shorter nocturnal sleep period and a longer daytime nap. Children with a longer nocturnal sleep period on weekends compared with weekdays had longer sleep latency and a later sleep onset time on weekdays, resulting in a lower sleep quality on weekends. An irregular bedtime on weekdays was associated with a later sleep onset time and a shorter sleep period on weekends. CONCLUSION: Sleep quality and schedule were linked with each other, which may explain why sleep problems tend to aggregate and form a wider syndrome of disturbed sleep even in young children. Strategies solely targeting the improvement of sleep quantity may not promote ideal sleep; simultaneous considerations for the sleep rhythm and quality may be required.

Hypothermia for neonatal encephalopathy: Nationwide Survey of Clinical Practice in Japan as of August 2010.

BACKGROUND: Therapeutic hypothermia is now recommended as a standard of care for neonatal encephalopathy. Although adherence to standard cooling protocols used in the phase-III trials is essential, empiric approaches have prevailed in Japan. AIM: To elucidate the gap between the standard cooling methods and the current practice in Japan. METHOD: In July 2010, a questionnaire regarding the practice of neonatal encephalopathy was mailed to clinical leads of registered neonatal intensive care units. RESULT: 56.2% of the units were incapable of offering therapeutic hypothermia because of the reasons such as the shortage of human/medical resources (85.1%) and limited number of cases (21.1%). Eighty-nine centres provided therapeutic hypothermia using either selective-head cooling (88.8%) or whole-body cooling (11.2%). Various target temperatures and cooling durations were used; 20.2% of the units cooled infants without using purpose-built equipments, whereas 14.6% did not continuously monitor the body temperature. DISCUSSION: Only 43.8% of the units provided therapeutic hypothermia. Even in centres where hypothermia was offered, adherence to the standard protocols was extremely poor. To secure the safety and efficacy, further promotion of the standard cooling protocols is required; an efficient cooling centre network has to be established by optimizing the work forth distribution and transportation system.

Admission temperature of very low birth weight infants and outcomes at three years old.

The lower body temperature of preterm newborns at admission to neonatal intensive care units (NICUs) is inversely associated with their morbidities and mortalities before discharge. This retrospective cohort study aimed to determine whether admission rectal temperature in very low birth weight infants (VLBWIs) is independently associated with a composite outcome of death or moderate-to-severe neurodevelopmental impairments as defined by a performance developmental quotient of < 70 at three years of age. VLBWIs admitted to the NICU between April 2010 and March 2016 were assesed. Developmental assessment was completed in 216 newborns. Nine and two infants died before and after discharge, respectively. A higher admission temperature was associated with a lower incidence of death or moderate-to-severe neurodevelopmental impairments with adjustment for gestational age, sex, antenatal steroid use, Apgar score, severe intraventricular hemorrhage, and severe bronchopulmonary dysplasia (odds ratio [OR] 0.424; 95% confidence interval [CI] 0.250-0.717; p = 0.001). The admission temperature remained as an independent variable of adverse outcome at three years of age even when the study cohort was limited to surviving infants (OR 0.448; 95% CI 0.259-0.774; p = 0.004). Further studies are needed to assess whether avoiding low body temperature at admission results in better long-term neurodevelopmental outcomes in VLBWIs.

Influence of Intrauterine Inflammation, Delivery, and Postnatal Feeding on the Temporal Changes of Serum Alpha 1 Acid Glycoprotein Levels in Extremely-Low-Birth-Weight Infants.

Infection remains the primary cause of death in extremely-low-birth-weight infants (ELBWIs). Alpha 1 acid glycoprotein (α1AG), an acute-phase protein, has been shown to be elevated in sporadic cases of septic ELBWIs prior to abnormal clinical signs. To delineate the roles of inflammation, delivery, and feeding in postnatal α1AG changes in ELBWIs, 75 ELBWIs of 26.5 ± 2.2 weeks of gestation born between May 2011 and August 2017 were retrospectively studied. The dependence of α1AG levels obtained on days 0−5 on the clinical variables was examined by incorporating interactions with age, followed by estimations of regression coefficients between clinical variables and α1AG levels at the early and late postnatal ages, defined by their standard deviation. Chorioamnionitis (p < 0.001), funisitis (p = 0.045), vaginal delivery (p = 0.025), enteral feeding (p = 0.022), and probiotics (p = 0.005) were associated with early α1AG elevations. Hypertensive disorder of pregnancy (p < 0.001) and gestational age (p = 0.001) were associated with late α1AG elevation; premature rupture of membranes (p < 0.001), funisitis (p = 0.021), body weight z-scores (p < 0.001), and enteral feeding (p = 0.045) were associated with late α1AG reduction. Postnatal α1AG changes in ELBWIs were associated with variables representative of age, growth, delivery, inflammation, and enteral feeding, potentially reflecting the process of sensitization to extrinsic microbes in utero, at birth, and thereafter.

Near-infrared light scattering and water diffusion in newborn brains.

OBJECTIVE: MRI provides useful information regarding brain maturation and injury in newborn infants. However, MRI studies are generally restricted during acute phase, resulting in uncertainty around upstream clinical events responsible for subtle cerebral injuries. Time-resolved near-infrared spectroscopy non-invasively provides the reduced scattering coefficient ( µ s ' ), which theoretically reflects tissue structural complexity. This study aimed to test whether µ s ' values of the newborn head reflected MRI findings. METHODS: Between June 2009 and January 2015, 77 hospitalised newborn infants (31.7 ± 3.8 weeks gestation) were assessed at 38.8 ± 1.3 weeks post-conceptional age. Associations of µ s ' values with MRI scores, mean diffusivity and fractional anisotropy were assessed. RESULTS: Univariable analysis showed that µ s ' values were associated with gestational week (p = 0.035; regression coefficient [B], 0.065; 95% confidence interval [CI], 0.005-0.125), fractional anisotropy in the cortical grey matter (p = 0.020; B, -5.994; 95%CI, -11.032 to -0.957), average diffusivity in the cortical grey matter (p < 0.001; B, -4.728; 95%CI, -7.063 to -2.394) and subcortical white matter (p = 0.001; B, -2.071; 95%CI, -3.311 to -0.832), subarachnoid space (p < 0.001; B, -0.289; 95%CI, -0.376 to -0.201) and absence of brain abnormality (p = 0.042; B, -0.422; 95%CI, -0.829 to -0.015). The multivariable model to explain µ s ' values comprised average diffusivity in the subcortical white matter (p < 0.001; B, -2.066; 95%CI, -3.200 to -0.932), subarachnoid space (p < 0.001; B, -0.314; 95%CI, -0.412 to -0.216) and absence of brain abnormality (p = 0.021; B, -0.400; 95%CI, -0.739 to -0.061). INTERPRETATION: Light scattering was associated with brain structure indicated by MRI-assessed brain abnormality and diffusion-tensor-imaging-assessed water diffusivity. When serially assessed in a larger population, µ s ' values might help identify covert clinical events responsible for subtle cerebral injury.

Three-year outcome following neonatal encephalopathy in a high-survival cohort.

This study investigated the 3-year clinical outcomes in relation to the severity of encephalopathy in high-survival infants who underwent therapeutic hypothermia. This retrospective observational study was conducted in level II/III neonatal intensive care units in Japan. The nationwide cohort included 474 infants registered in the Baby Cooling Registry of Japan between January 2012 and December 2016. Clinical characteristics, mortality rate and severe neurological impairment at age 3 years were evaluated. Of the infants, 48 (10.4%), 291 (63.1%) and 122 (26.5%) had mild, moderate and severe encephalopathy, respectively, upon admission. By age 3, 53 (11.2%) infants died, whereas 110 (26.1%) developed major disabilities. The mild group survived up to age 3. In the moderate group, 13 (4.5%) died and 44 (15.8%) developed major disabilities. In the severe group, 39 (32.0%) died by age 3. Adverse outcomes were observed in 100 (82.0%) infants. Mortality was relatively low in all subgroups, but the incidence of major disabilities was relatively high in the severe group. The relatively low mortality and high morbidity may be due to Japanese social and ethical norms, which rarely encourage the withdrawal of intensive life support. Cultural and ethical backgrounds may need to be considered when assessing the effect of therapeutic interventions.

Levothyroxine replacement therapy and refractory hypotension out of transitional period in preterm infants.

BACKGROUND: Recent studies suggest that refractory hypotension from causes other than septicaemia or cardiac failure is common in extremely preterm infants even out of the transitional period. Marked response to low-dose cortisol suggests underlying adrenal insufficiency, although the exact mechanism remains unknown. METHODS: To investigate potential triggers for and related short-term outcomes of early-onset (

Airway gas temperature within endotracheal tube can be monitored using rapid response thermometer.

Inappropriate preparation of respiratory gases is associated with serious complications during mechanical ventilation. To develop a temperature monitoring system of respiratory gases within the endotracheal tube, four newborn piglets were studied using an ultra-rapid-response thermometer attached to the closed endotracheal tube suction system. Respiratory gas temperatures were monitored at the mouth-corner level of the endotracheal tube using three thermocouples (Tairway, inserted into the endotracheal tube via the closed suction system; Ttube_centre and Ttube_wall, embedded within the endotracheal tube 0.5 mm and 1.6 mm from the tube wall, respectively). Univariate analysis showed that inspiratory Ttube_centre and inspiratory Ttube_wall were positively correlated with inspiratory Tairway (both p < 0.001). Multivariate analysis showed the dependence of inspiratory Tairway on inspiratory Ttube_centre and Ttube_wall and deflation of endotracheal tube cuff (p < 0.001, p = 0.001 and p = 0.046, respectively). Inspiratory gas temperature within the endotracheal tube can be monitored using a thermometer attached to the closed endotracheal tube suction system. Our system, with further validation, might help optimise respiratory gas humidification during mechanical ventilation.

Temporal inversion of the acid-base equilibrium in newborns: an observational study.

BACKGROUND: A considerable fraction of newborn infants experience hypoxia-ischaemia and metabolic acidosis at birth. However, little is known regarding the biological response of newborn infants to the pH drift from the physiological equilibrium. The aim of this study was to investigate the relationship between the pH drift at birth and postnatal acid-base regulation in newborn infants. METHODS: Clinical information of 200 spontaneously breathing newborn infants hospitalised at a neonatal intensive care centre were reviewed. Clinical variables associated with venous blood pH on days 5-7 were assessed. RESULTS: The higher blood pH on days 5-7 were explained by lower cord blood pH (-0.131, -0.210 to -0.052; regression coefficient, 95% confidence interval), greater gestational age (0.004, 0.002 to 0.005) and lower partial pressure of carbon dioxide on days 5-7 (-0.005, -0.006 to -0.004) (adjusted for sex, postnatal age and lactate on days 5-7). CONCLUSION: In relatively stable newborn infants, blood pH drift from the physiological equilibrium at birth might trigger a system, which reverts and over-corrects blood pH within the first week of life. Given that the infants within the study cohort was spontaneously breathing, the observed phenomenon might be a common reaction of newborn infants to pH changes at birth.

Influence of mothers' nighttime responses on the sleep-wake rhythm of 1-month-old infants.

The purpose of this study was to analyze the influence of the mothers' nighttime responses on the sleep-wake rhythm of their 1-month-old infants. This study used an anonymous self-administered survey questionnaire with 1133 mothers of 1-month-old infants. The questionnaire investigated basic information about the parents, growth environment of infants, mothers' sleep patterns during pregnancy, and infants' sleep patterns at the age of one month. Logistic regression analysis was used to analyze the influence of nighttime responses on the risk of infants sleeping longer during the day than at night. Regarding nighttime response behavior, it was found that immediately picking up 1-month-old infants results in longer sleep during the day than at night (OR 1.616 [1.017 - 2.566], p = 0.042), compared to delaying picking up the infant. It was suggested that the stimulation due to picking up an infant may affect sleep-wake rhythm formation.

Promoting sound development of preterm infants in the name of developmental neuroscience: Beyond advanced life support and neuroprotection.

Despite the increased survival opportunities for extremely preterm infants, their long-term cognitive outcomes remain poor, with increased incidence of cognitive impairments in childhood and reduced opportunities to attend higher education in young adulthood compared to their term-born peers. Given that a considerable fraction of preterm infants develop cognitive impairments even without apparent sentinel events at birth and cerebral lesions on MRI assessed at term equivalent age, future strategies to improve the outcome may need to address cerebral dysfunction, which cannot be explained by the classical understanding of the injury cascade triggered by hypoxia-ischaemia around birth. Developmental care has been proposed to minimize neurodevelopmental impairments related to preterm birth. However, considerable modes of cares, environmental settings and procedures provided by the developmental care of current style appear to offer little benefit to the sound development of infants. Although it is obvious that advanced life support and neuroprotective treatments fall far short in compensating for the burden of preterm birth, researchers need to make further effort to fill the knowledge gap in the cerebral function of foetuses and newborn infants before establishing evidence-based developmental care. Clinicians need to develop an ability to translate the findings from basic and translational studies incorporating their potential biases and limitations. Care for newborn infants needs to be reassessed, including but not limited to developmental care, in the context that any sensory input and motor reaction of preterm infants may ultimately affect their cognitive functioning.

Temporal changes and control variables of growth differentiation factor 15 levels during the first week of life in hospitalised newborn infants.

Serum growth differentiation factor 15 (GDF15) is a useful biomarker of mitochondrial diseases; its utility in newborns remains unknown. To investigate the temporal change in GDF15 within the first week of life, and to identify its potential control variables, blood samples were obtained from 18 newborns. The GDF15 levels declined to approximately 35% of the cord blood levels within the first week of life and were negatively correlated with postnatal age and Z-score of birth weight but were positively correlated with N-terminal pro-brain natriuretic peptide and lactate levels. GDF15 levels may reflect the progress of postnatal transition to aerobic metabolism.