Abstract
Background
Early identification of newborns at risk for respiratory support remains challenging. Lung ultrasound (LUS) provides real-time information on pulmonary aeration, while right diaphragmatic ultrasound evaluates respiratory muscle function.
Objectives
To assess whether lung and right diaphragmatic ultrasound findings obtained at one hour of life differed between term and near-term newborns who subsequently required free-flow oxygen supplementation within the first 48 h after birth and those who did not.
Methods
This prospective observational study included term and near-term newborns undergoing standardized lung ultrasound and right diaphragmatic ultrasound at one hour of life. Lung ultrasound was performed using a six-region protocol with a 0–3 scoring system. Right diaphragmatic function was assessed by diaphragmatic thickening fraction and excursion. The primary outcome was the requirement for free-flow oxygen supplementation at any time during the first 48 h of life. Continuous variables are reported as median and interquartile range (IQR), and categorical variables as counts and percentages. Group comparisons, logistic regression, and receiver operating characteristic (ROC) curve analysis were performed.
Results
A total of 121 newborns underwent ultrasound assessment at one hour of life. Free-flow oxygen supplementation within the first 48 h was required in 28 newborns (23.1%). Lung ultrasound score at one hour was significantly higher in newborns requiring oxygen than in those who did not (10.5 [IQR 9–11] vs. 7 [IQR 5–8], p < 0.001). Right diaphragmatic thickening fraction was 21.5% (IQR 17.2–24.1) in the oxygen group and 20.0% (IQR 18.2–22.7) in the no oxygen group, while right diaphragmatic excursion was 5.55 mm (IQR 5.25–5.8) and 5.6 mm (IQR 5.3–6.1), respectively; neither differed significantly between groups. In multivariable analysis adjusting for gestational age and cesarean delivery, lung ultrasound score remained significantly associated with subsequent oxygen requirement (adjusted OR 3.41 per one-point increase, 95% CI 2.08–5.60, p < 0.001). ROC analysis showed promising discriminatory performance in this exploratory cohort, with an AUC of 0.94 (95% CI 0.85–0.99); a lung ultrasound score threshold of 9 provided 89.3% sensitivity and 88.2% specificity.
Conclusions
In this cohort of term and near-term newborns, a higher lung ultrasound score at one hour of life was significantly associated with subsequent free-flow oxygen requirement within the first 48 h and showed promising discriminatory performance in this exploratory cohort. In contrast, right diaphragmatic ultrasound parameters did not clearly differentiate between groups. These findings support the potential role of early lung ultrasound in neonatal respiratory risk stratification, but external validation in larger prospective cohorts is required.
Supplementary Information
The online version contains supplementary material available at 10.1186/s13052-026-02313-7.
Keywords: Lung ultrasound, Newborn, Neonatal respiratory transition, Oxygen requirement, Respiratory distress, Point-of-care ultrasound
Significance
What is known: Lung ultrasound can identify abnormalities of neonatal lung aeration during early postnatal transition and has been associated with subsequent respiratory morbidity and need for respiratory support. The role of diaphragmatic ultrasound in term and near-term newborns during the first hours after birth remains less well defined. What is new: In term and near-term newborns assessed at one hour of life, a higher lung ultrasound score was significantly associated with subsequent free-flow oxygen requirement within the first 48 hours and showed promising discriminatory performance in this exploratory cohort. Right diaphragmatic thickening fraction and excursion measured at one hour of life did not clearly differentiate newborns who later required oxygen from those who did not.
Supplementary Information
The online version contains supplementary material available at 10.1186/s13052-026-02313-7.
Introduction
The transition from intrauterine to extrauterine life represents a critical physiological period for the newborn, particularly with respect to respiratory adaptation. At birth, the neonatal lungs must rapidly clear fetal lung fluid, establish functional residual capacity, and initiate effective gas exchange [1, 2]. Although this process is usually successful in term and near-term infants, a subset of newborns experience delayed pulmonary adaptation, leading to early respiratory distress and the need for supplemental oxygen within the first hours of life. Several studies have demonstrated that lung ultrasound provides a reliable assessment of pulmonary aeration during early neonatal transition and may be associated with subsequent respiratory support needs [2–12]. Early identification of newborns at risk for respiratory compromise remains a significant clinical challenge in neonatal practice [1, 7, 8]. Lung ultrasound should be considered as a complementary bedside tool and not as a replacement for clinical examination in neonatal respiratory assessment.
Current international guidelines emphasize close clinical monitoring during neonatal transition; however, decision-making regarding respiratory support is largely reactive and based on clinical observation rather than objective early predictors [7, 8]. Assessment of neonatal respiratory status in the delivery room and early postnatal period relies predominantly on parameters such as respiratory rate, work of breathing, oxygen saturation, and Apgar scores. These measures are inherently subjective, may vary between observers, and often fail to accurately predict the subsequent need for respiratory support. Moreover, commonly used clinical scores were not designed to detect subtle disturbances in lung aeration during the immediate postnatal transition [9]. As a result, some newborns who initially appear clinically stable may later require oxygen supplementation, while others may undergo unnecessary monitoring or intervention.
Chest radiography has traditionally been considered the reference imaging modality for evaluating neonatal lung pathology. Nevertheless, its routine use in the early postnatal period is limited by radiation exposure, logistical constraints, and limited sensitivity for detecting early or mild disturbances in lung aeration. In this context, lung ultrasound (LUS) has emerged as a valuable bedside imaging technique for neonatal respiratory assessment. LUS is non-invasive, radiation-free, repeatable, and can be performed at the point of care, making it particularly well suited for use in the delivery room and neonatal intensive care unit.
Over the past decade, multiple studies have demonstrated the utility of lung ultrasound in diagnosing neonatal respiratory conditions such as transient tachypnea of the newborn and respiratory distress syndrome [10–14]. Interpretation of LUS is based on well-established sonographic artifacts, including A-lines, B-lines, white lung patterns, and consolidations, which reflect the degree of lung aeration and interstitial or alveolar involvement. Quantitative lung ultrasound scoring systems have been developed to standardize assessment and improve reproducibility, showing good correlation with oxygenation indices and clinically relevant outcomes.
Despite growing evidence supporting the diagnostic role of lung ultrasound, its role in early postnatal risk stratification remains insufficiently explored. Most existing studies evaluate LUS after the onset of respiratory symptoms or following initiation of respiratory support. Data regarding the clinical relevance of LUS performed within the first hour of life—before overt clinical deterioration—remain limited. Early sonographic findings associated with subsequent oxygen requirement may help refine monitoring strategies and improve resource allocation during neonatal respiratory transition.
In parallel with lung aeration, diaphragmatic function plays a crucial role in neonatal respiration. The diaphragm is the primary respiratory muscle in newborns, and its efficiency directly influences tidal volume and work of breathing [15–18]. Ultrasound assessment of diaphragmatic excursion and diaphragmatic thickening fraction has been increasingly used in adult and pediatric populations to evaluate respiratory muscle performance. In neonates, however, the clinical relevance of right diaphragmatic ultrasound parameters during early postnatal transition remains unclear, and evidence regarding their association with early respiratory outcomes remains limited.
Therefore, the primary aim of this prospective observational study was to evaluate whether lung ultrasound findings obtained at one hour of life differed between term and near-term newborns who subsequently required free-flow oxygen supplementation during the first 48 h after birth and those who did not. Secondary objectives included evaluating whether right diaphragmatic ultrasound parameters—diaphragmatic excursion and thickening fraction—differed according to subsequent oxygen requirement.
Materials and methods
Study design
This was a prospective, single-center, observational study conducted in the Neonatology Department of a tertiary academic hospital. The study was designed to assess the association between early lung ultrasound findings obtained at one hour of life and subsequent free-flow oxygen requirement during the first 48 h after birth in term and near-term newborns. Right diaphragmatic ultrasound parameters were evaluated as exploratory secondary variables.
The study followed the principles of the Declaration of Helsinki and was approved by the local Ethics Committee (approval number: 585/08.12.2025). Written informed consent was obtained from the parents or legal guardians of all newborns prior to inclusion.
Study population
All eligible newborns were enrolled consecutively during the study period. Term and near-term newborns admitted to the postnatal ward were screened for eligibility between December 2025 and February 2026. Inclusion criteria were: gestational age ≥ 35 weeks, singleton birth, and clinical stability during the first hour of life. Clinical stability was defined as spontaneous breathing with a heart rate greater than 100 beats per minute, absence of significant respiratory distress, and no requirement for positive pressure ventilation or continuous positive airway pressure during the first hour of life. Both vaginally delivered and cesarean-born infants were eligible for inclusion.
Newborns were excluded if they had major congenital malformations, including thoracic or abdominal malformations, congenital diaphragmatic anomalies, or known chromosomal abnormalities. Additional exclusion criteria were hemodynamic instability requiring vasoactive support, need for invasive or non-invasive respiratory support within the first hour of life, suspected or confirmed congenital heart disease, or incomplete clinical or ultrasound data. Newborns with malformations potentially affecting respiratory mechanics or lung aeration were excluded to avoid confounding effects on ultrasound measurements.
A total of 121 newborns met the eligibility criteria and underwent ultrasound assessment at one hour of life. Newborns were followed clinically for the first 48 h and stratified according to whether free-flow oxygen supplementation was required during this period.
Clinical data collection and outcome definition
Baseline demographic and perinatal data were prospectively collected, including gestational age, birth weight, sex, mode of delivery, and Apgar score at five minutes. The Apgar score at five minutes was selected as it more accurately reflects postnatal adaptation and has greater prognostic relevance than the one-minute score.
Free-flow oxygen was defined as supplemental oxygen delivered via oxygen hood or nasal cannula without the application of positive airway pressure. The primary outcome was the requirement for free-flow oxygen supplementation at any time during the first 48 h of life. The decision to initiate oxygen therapy was made by the attending neonatologist based on routine clinical assessment, including pulse oximetry and the overall signs of respiratory transition, and was independent of the ultrasound findings, which were not used to guide clinical management. In our institution, free-flow oxygen supplementation was initiated when preductal SpO₂ was persistently below 90%, in conjunction with routine clinical assessment of respiratory transition or respiratory distress. The decision to initiate oxygen therapy was made by the attending neonatologist and was not based on a rigid study-specific protocol. Because oxygen initiation was clinically determined and not based on a fully prespecified study algorithm for study purposes, potential variation in clinical decision-making was considered in the interpretation of the results. The 48-hour follow-up period was selected to capture early postnatal respiratory adaptation while minimizing confounding effects related to later-onset respiratory or infectious conditions.
Lung ultrasound protocol
Lung ultrasound examinations were performed by a single experienced operator, a senior academic physician with more than five years of experience in neonatal and pediatric ultrasound, who had performed over 500 lung ultrasound examinations prior to study initiation. All ultrasound assessments were conducted using a Samsung HS40 ultrasound system (Samsung Medison, South Korea) equipped with a high-frequency linear probe for lung evaluation. The ultrasound examinations were performed before the occurrence of the primary outcome, and the operator was not involved in clinical decision-making regarding oxygen supplementation. The ultrasound operator was therefore blinded to subsequent clinical management decisions regarding oxygen supplementation.
Examinations were systematically performed with the newborn placed in the supine position (dorsal decubitus). All assessments were carried out while the newborns were in a calm behavioral state, without signs of psychomotor agitation or crying, in order to minimize motion artifacts and variability in lung aeration related to respiratory effort. The exact timing of feeding relative to ultrasound assessment was not standardized, and body temperature was not continuously monitored during the examination.
A standardized lung ultrasound protocol was applied, based on previously published and validated neonatal lung ultrasound scoring systems. Each hemithorax was divided into three regions—anterior superior, anterior inferior, and lateral—resulting in a total of six lung regions evaluated bilaterally [2–4, 9–12]. This six-region approach has been previously validated in neonatal populations and allows for rapid, reproducible assessment of lung aeration during early postnatal transition. The ultrasound probe was positioned longitudinally in the intercostal spaces, perpendicular to the ribs, to ensure optimal visualization of pleural line artifacts.
For each lung region, the worst ultrasound pattern observed was recorded and scored according to a semiquantitative lung ultrasound score (LUS), as follows:
Score 0: presence of A-lines with normal lung sliding;
Score 1: presence of fewer than three isolated B-lines per intercostal space;
Score 2: presence of multiple (three or more) B-lines per intercostal space or coalescent B-lines;
Score 3: white lung pattern or lung consolidation
The total lung ultrasound score was calculated by summing the scores of all six regions, with higher scores reflecting poorer lung aeration. In accordance with the study protocol, ultrasound images were stored only when abnormal findings were present, defined as a lung ultrasound score greater than zero in the evaluated region. This approach was chosen to ensure focused documentation of clinically relevant sonographic abnormalities while maintaining standardized image acquisition. This approach is consistent with the institutional image archiving policy, which prioritizes the storage of clinically relevant abnormal findings while maintaining efficient data management.
Lung ultrasound assessments were completed within a predefined time window centered around one hour of life and were not communicated to the clinical team responsible for patient management. Consequently, lung ultrasound results did not influence clinical decision-making regarding oxygen supplementation or other aspects of neonatal care. Interobserver variability was not formally assessed, as all examinations were performed by a single experienced operator, ensuring internal consistency of measurements.
Diaphragmatic ultrasound assessment
Diaphragmatic ultrasound assessment was performed immediately after lung ultrasound, during the same examination session, using the Samsung HS40 ultrasound system (Samsung Medison, South Korea). Two different transducers were used according to the measured parameter, in order to optimize image quality and measurement accuracy. All measurements were obtained by the same experienced operator to ensure consistency and reduce measurement variability.
The diaphragm was examined using a subcostal and intercostal approach along the anterior axillary line, with the ultrasound probe positioned to visualize the zone of apposition between the diaphragm and the rib cage. The right hemidiaphragm was preferentially assessed due to the superior acoustic window provided by the liver and improved reproducibility compared with the left side, as commonly reported in neonatal ultrasound studies.
Diaphragmatic excursion was assessed using a microconvex probe and measured with M-mode ultrasonography, with the ultrasound beam oriented perpendicular to the diaphragmatic dome [15–18]. Excursion was defined as the vertical displacement of the diaphragm between end-expiration and end-inspiration and was expressed in millimeters. Three consecutive respiratory cycles were recorded, and the mean value was used for analysis. Averaging multiple respiratory cycles was chosen to reduce variability related to irregular neonatal breathing patterns.
Diaphragmatic thickness was evaluated using a high-frequency linear probe specifically suitable for neonatal imaging, smaller than those commonly used in adult populations. Thickness was measured at end-expiration and end-inspiration in the zone of apposition using B-mode imaging. Diaphragmatic thickening fraction (DTF) was calculated according to the following formula:
 |
This parameter reflects diaphragmatic contractile activity and has been proposed as a surrogate marker of respiratory muscle function. Although diaphragmatic thickening fraction has been primarily validated in adult populations, emerging evidence suggests that it may provide insights into diaphragmatic contractile activity in neonates during early respiratory adaptation.
All diaphragmatic ultrasound examinations were performed with the newborns in the supine position, during quiet spontaneous breathing, without crying or agitation. No sedatives were administered. Diaphragmatic ultrasound measurements were recorded at approximately one hour of life and were not communicated to the clinical team responsible for patient management. Diaphragmatic ultrasound was considered an exploratory assessment and was not intended to guide clinical management in this study.
Interobserver variability was not assessed, as all examinations were conducted by a single experienced operator, ensuring internal consistency of diaphragmatic measurements.
Statistical analysis
Descriptive and inferential analyses were performed after verification of the analytical dataset. Continuous variables were assessed for distribution and are presented as median and interquartile range (IQR), as most variables were not normally distributed. Categorical variables are presented as counts and percentages.
Between-group comparisons (newborns requiring free-flow oxygen supplementation within the first 48 h versus those who did not) were performed using the Mann–Whitney U test for continuous variables and the chi-square test or Fisher’s exact test, as appropriate, for categorical variables. Two-sided p values < 0.05 were considered statistically significant.
To explore the discriminatory performance of lung ultrasound score at one hour of life for subsequent oxygen requirement, receiver operating characteristic (ROC) curve analysis was performed and the area under the curve (AUC) with 95% confidence intervals (CI) was calculated.
Logistic regression analysis was used to evaluate the association between lung ultrasound score and subsequent oxygen requirement. Univariable logistic regression was first performed. A multivariable logistic regression model was then constructed adjusting for gestational age and mode of delivery, which were considered clinically relevant potential confounders. Odds ratios (OR) with 95% confidence intervals are reported.
Right diaphragmatic ultrasound parameters were analyzed in an exploratory manner. Given the limited number of outcome events, these analyses were interpreted cautiously.
Missing data were handled by complete-case analysis. All analyses were performed using Python (version 3.10; Python Software Foundation) with standard statistical packages.
Sample size considerations
As this was an exploratory prospective observational study, no formal a priori sample size calculation was performed. The study sample was determined by the number of eligible consecutive newborns admitted during the predefined study period. A total of 28 newborns required free-flow oxygen supplementation within the first 48 h, allowing only limited adjusted modeling. Therefore, the inferential analyses were considered exploratory and hypothesis-generating.
Results
Study flow and outcome
Of the 121 enrolled newborns assessed at one hour of life, 28 (23.1%) required free-flow oxygen supplementation within the first 48 h, whereas 93 (76.9%) did not.
The study flow and stratification according to oxygen requirement are illustrated in Fig. 1.
Fig. 1.
Study flow and stratification of newborns according to free-flow oxygen requirement within the first 48 h of life
Baseline characteristics and ultrasound findings at 1 h
Baseline clinical characteristics and ultrasound findings at one hour of life according to oxygen requirement are summarized in Table 1. Gestational age, birth weight, sex distribution, mode of delivery, and Apgar score at 5 min did not differ significantly between groups (all p > 0.05), although cesarean delivery was more frequent in newborns who subsequently required oxygen supplementation. Lung ultrasound score at one hour was significantly higher in newborns who subsequently required free-flow oxygen supplementation within the first 48 h than in those who did not (10.5 [IQR 9–11] vs. 7 [IQR 5–8], p < 0.001). In contrast, right diaphragmatic thickening fraction (21.5% [IQR 17.2–24.1] vs. 20.0% [IQR 18.2–22.7], p = 0.995) and right diaphragmatic excursion (5.55 mm [IQR 5.25–5.8] vs. 5.6 mm [IQR 5.3–6.1], p = 0.418) did not differ significantly between groups.
Table 1.
Baseline clinical characteristics and ultrasound parameters at one hour of life according to oxygen requirement
| Variable | No oxygen (n = 93) | Oxygen required (n = 28) | p value |
|---|---|---|---|
| Gestational age, weeks | 39 (38–39) | 38.5 (38–39) | 0.599 |
| Birth weight, g | 3280 (3000–3570) | 3310 (2955–3743) | 0.595 |
| Male sex, n (%) | 48 (51.6) | 17 (60.7) | 0.528 |
| Cesarean delivery, n (%) | 70 (76.1) | 24 (85.7) | 0.432 |
| Apgar score at 5 min | 10 (10–10) | 10 (10–10) | 0.076 |
| Lung ultrasound score at 1 h | 7 (5–8) | 10.5 (9–11) | < 0.001 |
| Right diaphragmatic thickening fraction at 1 h, % | 20.0 (18.2–22.7) | 21.5 (17.2–24.1) | 0.995 |
| Right diaphragmatic excursion at 1 h, mm | 5.6 (5.3–6.1) | 5.55 (5.25–5.8) | 0.418 |
The distribution of lung ultrasound score at one hour according to subsequent free-flow oxygen requirement is shown in Fig. 2.
Fig. 2.
Distribution of lung ultrasound score at one hour of life according to subsequent free-flow oxygen requirement within the first 48 h
Mode of delivery was missing for one newborn in the no oxygen group; percentages were calculated using available data. Continuous variables are presented as median (IQR) and were compared using the Mann–Whitney U test. Categorical variables are presented as n (%) and were compared using the chi-square test or Fisher’s exact test, as appropriate.
Association between lung ultrasound score and subsequent oxygen requirement
In univariable logistic regression analysis, a higher lung ultrasound score at one hour of life was significantly associated with subsequent free-flow oxygen requirement within the first 48 h (OR 3.44 per one-point increase, 95% CI 2.09–5.65, p < 0.001). In a multivariable logistic regression model adjusting for gestational age and cesarean delivery, lung ultrasound score remained significantly associated with subsequent oxygen requirement (adjusted OR 3.41 per one-point increase, 95% CI 2.08–5.60, p < 0.001). Gestational age (adjusted OR 0.97, 95% CI 0.63–1.49, p = 0.896) and cesarean delivery (adjusted OR 1.33, 95% CI 0.27–6.46, p = 0.723) were not significantly associated with the outcome. The adjusted model included 120 newborns because mode of delivery was missing in one case.
Discriminatory performance of lung ultrasound score
Receiver operating characteristic (ROC) curve analysis suggested potentially strong discriminatory performance of lung ultrasound score at one hour of life for subsequent free-flow oxygen requirement within the first 48 h, with an area under the curve (AUC) of 0.94 (95% CI 0.85–0.99). A lung ultrasound score threshold of 9 provided the best balance between sensitivity and specificity, with a sensitivity of 89.3% and a specificity of 88.2%. The ROC curve is shown in Fig. 3.
Fig. 3.
Receiver operating characteristic (ROC) curve of lung ultrasound score at one hour of life for subsequent free-flow oxygen requirement within the first 48 h. The area under the curve (AUC) was 0.94 (95% CI 0.85–0.99). A lung ultrasound score threshold of 9 provided 89.3% sensitivity and 88.2% specificity
Discussion
In this cohort of term and near-term newborns assessed at one hour of life, newborns who subsequently required free-flow oxygen within the first 48 h had significantly higher lung ultrasound scores than those who did not. In contrast, right diaphragmatic ultrasound parameters showed overlapping distributions between groups and were not significantly associated with the outcome. In multivariable analysis adjusting for gestational age and cesarean delivery, lung ultrasound score remained significantly associated with subsequent oxygen requirement, whereas gestational age and mode of delivery did not. ROC analysis also suggested potentially strong discriminatory performance of lung ultrasound score at one hour of life for identifying newborns who later required free-flow oxygen supplementation. However, this estimate should be interpreted cautiously because it was derived from a small exploratory single-center cohort with only 28 outcome events and may be optimistic in the absence of external validation.
These findings support the clinical relevance of early lung ultrasound assessment during neonatal respiratory transition. Lung ultrasound is rapid, non-invasive, radiation-free, and suitable for bedside use in the delivery room and postnatal ward. In our cohort, higher lung ultrasound scores at one hour of life were associated with subsequent oxygen requirement during the first 48 h, suggesting that early sonographic assessment of lung aeration may help refine monitoring strategies in newborns at risk of delayed respiratory adaptation.
Our findings are consistent with prior neonatal lung ultrasound studies showing that abnormal or higher early lung ultrasound scores are associated with impaired lung aeration and with subsequent need for respiratory support, particularly in newborns with transient tachypnea of the newborn or respiratory distress syndrome [3, 4, 9–12]. Studies performed immediately after birth have also shown that lung ultrasound can characterize normal postnatal transition and identify delayed lung fluid clearance during the first hours of life [2, 9, 12]. Compared with those reports, our study specifically focused on term and near-term newborns systematically assessed at one hour of life and evaluated free-flow oxygen requirement within the first 48 h as a pragmatic early clinical outcome. The high rate of cesarean delivery in our cohort, particularly among newborns who later required oxygen supplementation, is clinically plausible and deserves consideration. Cesarean birth is known to be associated with delayed clearance of fetal lung fluid and transient respiratory morbidity in the early neonatal period [2, 9, 12]. In our cohort, however, cesarean delivery was not independently associated with oxygen requirement after adjustment, whereas lung ultrasound score remained significantly associated with the outcome.
This suggests that early lung aeration assessed directly by ultrasound may provide more relevant bedside information than delivery mode alone.
In contrast to lung ultrasound findings, right diaphragmatic thickening fraction and excursion did not differ significantly between groups. These negative findings should be interpreted cautiously. Diaphragmatic ultrasound was included as an exploratory secondary assessment, and the number of outcome events was limited. It is possible that diaphragmatic function at one hour of life remains relatively homogeneous in term and near-term newborns during early respiratory transition, or that subtle differences are not readily captured by single-time-point measurements in this clinical setting.
Several limitations should be acknowledged. First, this was a single-center study with a relatively limited sample size and only 28 outcome events, which restricted the complexity of adjusted modeling. Although gestational age and mode of delivery were selected a priori as the most clinically relevant covariates, residual confounding by other factors such as sex, birth weight, Apgar score, and early clinical signs of respiratory transition cannot be excluded. Second, the primary outcome partly depended on clinician judgment and local practice patterns regarding oxygen initiation. Although preductal SpO₂ below 90% was used in routine practice, oxygen initiation was not governed by a rigid study-specific algorithm, which may have introduced management-related variability and may limit external generalizability. Third, all ultrasound examinations were performed by a single experienced operator, and interobserver variability was not assessed. Therefore, the reproducibility of these measurements across operators and centers remains uncertain, which limits generalizability and should be addressed in future validation studies. Fourth, ultrasound examinations were performed at a single early time point, which did not allow evaluation of dynamic changes over time. Finally, image archiving was incomplete for normal lung ultrasound examinations, reflecting institutional archiving practice.
The strengths of this study include its prospective design, standardized ultrasound assessment performed at a fixed early time point, blinding of clinical management to ultrasound findings, and inclusion of both lung and right diaphragmatic ultrasound parameters. The study also addresses a clinically relevant question in a population of term and near-term newborns during early postnatal respiratory transition.
Future multicenter studies with larger and more diverse neonatal populations are needed to externally validate these findings. Serial ultrasound assessments may provide further insight into the dynamics of lung aeration and diaphragmatic function during postnatal adaptation. Additional work is also needed to determine whether early lung ultrasound findings can be integrated into structured neonatal monitoring pathways or bedside decision-support strategies.
Conclusions
In this cohort of term and near-term newborns, a higher lung ultrasound score at one hour of life was significantly associated with subsequent free-flow oxygen requirement within the first 48 h and showed promising discriminatory performance in this exploratory cohort. In contrast, right diaphragmatic ultrasound parameters did not clearly differentiate between groups. These findings support the potential role of early lung ultrasound in neonatal respiratory risk stratification, but external validation in larger prospective cohorts is required.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgements
The authors used ChatGPT (OpenAI, San Francisco, CA, USA) exclusively to improve the language and readability of the manuscript. All scientific content, interpretations, and conclusions are the original work of the authors.
Author contributions
Conceptualization, B.R. and D.I.; Methodology, B.R. and D.I.; Investigation, B.R., A.R., M.D., I.E., B.C., M.Ș. and O.R.; Formal analysis, B.R.; Data curation, B.R. and A.R.; Writing—original draft, B.R.; Writing—review and editing, all authors; Supervision, D.I.; Project administration, B.R. and D.I. All authors have read and agreed to the published version of the manuscript.
Funding
We would like to acknowledge Victor Babeș University of Medicine and Pharmacy Timișoara for their support in covering the costs of publication for this research paper.
Data availability
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.
Declarations
Ethics approval and consent to participate
The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee (approval number: 585/08.12.2025). Written informed consent was obtained from the parents or legal guardians of all newborns prior to inclusion.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
- 1.Hooper SB, te Pas AB, Kitchen MJ. Respiratory transition in the newborn: a three-phase process. Arch Dis Child Fetal Neonatal Ed. 2016;101(3):F266–71. 10.1136/archdischild-2013-305704. [DOI] [PubMed] [Google Scholar]
- 2.Blank DA, Rogerson SR, Kamlin COF, Fox LM, Lorenz L, Kane SC, et al. Lung ultrasound during the initiation of breathing in healthy term and late preterm infants immediately after birth, a prospective, observational study. Resuscitation. 2017;114:59–65. 10.1016/j.resuscitation.2017.02.017. [DOI] [PubMed] [Google Scholar]
- 3.Raimondi F, Migliaro F, Sodano A, Ferrara T, Lama S, Vallone G, et al. Use of neonatal chest ultrasound to predict noninvasive ventilation failure. Pediatrics. 2014;134(4):e1089–94. 10.1542/peds.2013-3924. [DOI] [PubMed] [Google Scholar]
- 4.Brat R, Yousef N, Klifa R, Reynaud S, Shankar Aguilera S, De Luca D. Lung ultrasonography score to evaluate oxygenation and surfactant need in neonates treated with continuous positive airway pressure. JAMA Pediatr. 2015;169(8):e151797. 10.1001/jamapediatrics.2015.1797. [DOI] [PubMed] [Google Scholar]
- 5.De Luca D, Yousef N, Cattarossi L. Ultrasound of the lung in neonates: what is new? Eur J Pediatr. 2018;177(3):347–55. 10.1007/s00431-017-3054-1. [Google Scholar]
- 6.Raimondi F, Yousef N, Migliaro F, Capasso L, De Luca D. Point-of-care lung ultrasound in neonatology: classification into descriptive and functional applications. Pediatr Res. 2021;90(3):524–31. 10.1038/s41390-018-0114-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Singh Y, Tissot C, Fraga MV, Yousef N, Gonzalez Cortes R, Lopez J, et al. International evidence-based guidelines on Point of Care Ultrasound (POCUS) for critically ill neonates and children issued by the POCUS Working Group of the European Society of Paediatric and Neonatal Intensive Care (ESPNIC). Crit Care. 2020;24(1):65. 10.1186/s13054-020-2787-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Volpicelli G, Elbarbary M, Blaivas M, Lichtenstein DA, Mathis G, Kirkpatrick AW, et al. International evidence-based recommendations for point-of-care lung ultrasound. Intensive Care Med. 2012;38(4):577–91. 10.1007/s00134-012-2513-4. [DOI] [PubMed] [Google Scholar]
- 9.Blank DA, Kamlin COF, Rogerson SR, Fox LM, Lorenz L, Kane SC, et al. Lung ultrasound immediately after birth to describe normal neonatal transition: an observational study. Arch Dis Child Fetal Neonatal Ed. 2018;103(2):F157–62. 10.1136/archdischild-2017-312818. [DOI] [PubMed] [Google Scholar]
- 10.Corsini I, Parri N, Gozzini E, Coviello C, Leonardi V, Poggi C, et al. Lung ultrasound for the differential diagnosis of respiratory distress in neonates. Neonatology. 2019;115(1):77–84. 10.1159/000493001. [DOI] [PubMed] [Google Scholar]
- 11.Vergine M, Copetti R, Brusa G, Cattarossi L. Lung ultrasound accuracy in respiratory distress syndrome and transient tachypnea of the newborn. Neonatology. 2014;106(2):87–93. 10.1159/000358227. [DOI] [PubMed] [Google Scholar]
- 12.Raimondi F, Migliaro F, Sodano A, Umbaldo A, Romano A, Vallone G, Capasso L. Can neonatal lung ultrasound monitor fluid clearance and predict the need of respiratory support? Crit Care. 2012;16(6):R220. 10.1186/cc11865. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Copetti R, Cattarossi L, Macagno F, Violino M, Furlan R. Lung ultrasound in respiratory distress syndrome: a useful tool for early diagnosis. Neonatology. 2008;94(1):52–9. 10.1159/000113059. [DOI] [PubMed] [Google Scholar]
- 14.Hiles M, Culpan AM, Watts C, Munyombwe T, Wolstenhulme S. Neonatal respiratory distress syndrome: chest X-ray or lung ultrasound? A systematic review. Ultrasound. 2017;25(2):80–91. 10.1177/1742271X16689374. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Llamas-Álvarez AM, Tenza-Lozano EM, Latour-Pérez J. Diaphragm and lung ultrasound to predict weaning outcome: systematic review and meta-analysis. Chest. 2017;152(6):1140–50. 10.1016/j.chest.2017.08.028. [DOI] [PubMed] [Google Scholar]
- 16.Vivier E, MekontsoDessap A, Dimassi S, Vargas F, Lyazidi A, Thille AW, Brochard L. Diaphragm ultrasonography to estimate the work of breathing during non-invasive ventilation. Intensive Care Med. 2012;38(5):796–803. 10.1007/s00134-012-2547-7. [DOI] [PubMed] [Google Scholar]
- 17.Goligher EC, Fan E, Herridge MS, Murray A, Vorona S, Brace D, et al. Evolution of diaphragm thickness during mechanical ventilation. Impact of inspiratory effort. Am J Respir Crit Care Med. 2015;192(9):1080–8. 10.1164/rccm.201503-0620OC. [DOI] [PubMed] [Google Scholar]
- 18.Umbrello M, Formenti P. Ultrasonographic assessment of diaphragm function in critically ill subjects. Respir Care. 2016;61(4):542–55. 10.4187/respcare.04412. [DOI] [PubMed] [Google Scholar]
Associated Data
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Supplementary Materials
Data Availability Statement
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.