Non-conditioned cord blood transplantation for infection control in athymic CHARGE syndrome.

OBJECTIVE: CHARGE syndrome is a congenital malformation syndrome caused by heterozygous mutations in the CHD7 gene. Severe combined immunodeficiency (SCID) arises from congenital athymia called CHARGE/complete DiGeorge syndrome. While cultured thymus tissue implantation (CTTI) provides an immunological cure, hematopoietic cell transplantation (HCT) is an alternative option for immuno-reconstitution of affected infants. We aimed to clarify the clinical outcomes of patients with athymic CHARGE syndrome after HCT. METHODS: We studied the immunological reconstitution and outcomes of four patients who received non-conditioned unrelated donor cord blood transplantation (CBT) at Kyushu University Hospital from 2007 to 2022. The posttransplant outcomes were compared with the outcomes of eight reported patients. RESULTS: Four index cases received CBT 70-144 days after birth and had no higher than grade II acute graft-versus-host disease. One infant was the first newborn-screened athymic case in Japan. They achieved more than 500/µL naïve T cells with balanced repertoire 1 month post transplant, and survived more than 12 months with home care. Twelve patients including the index cases received HCT at a median 106 days after birth (range: 70-195 days). One-year overall survival rate was significantly higher in patients who underwent non-conditioned HCT than in those who received conditioned HCT (100% vs. 37.5%, p = .02). Nine patients died, and the major cause of death was cardiopulmonary failure. CONCLUSIONS: Athymic infants achieved a prompt reconstitution of non-skewing naïve T cells after non-conditioned CBT that led to home care in infancy without significant infections. Non-conditioned CBT is a useful bridging therapy for newborn-screened cases toward an immunological cure by CTTI.

Divergent neurodevelopmental profiles of very-low-birth-weight infants.

BACKGROUND: Advanced perinatal medicine has decreased the mortality rate of preterm infants. Long-term neurodevelopmental outcomes of very-low-birth-weight infants (VLBWIs) remain to be investigated. METHODS: Participants were 124 VLBWIs who had in-hospital birth from 2007 to 2015. Perinatal information, developmental or intelligence quotient (DQ/IQ), and neurological comorbidities at ages 3 and 6 years were analyzed. RESULTS: Fifty-eight (47%) VLBWIs received neurodevelopmental assessments at ages 3 and 6 years. Among them, 15 (26%) showed DQ/IQ <75 at age 6 years. From age 3 to 6 years, 21 (36%) patients showed a decrease (≤-10), while 5 (9%) showed an increase (≥+10) in DQ/IQ scores. Eight (17%) with autism spectrum disorder or attention-deficit hyperactivity disorder (ASD/ADHD) showed split courses of DQ/IQ, including two with ≤-10 and one with +31 to their scores. On the other hand, all 7 VLBWIs with cerebral palsy showed DQ ≤35 at these ages. Magnetic resonance imaging detected severe brain lesions in 7 (47%) of those with DQ <75 and 1 (18%) with ASD/ADHD. CONCLUSIONS: VLBWIs show a broad spectrum of neurodevelopmental outcomes after 6 years. These divergent profiles also indicate that different risks contribute to the development of ASD/ADHD from those of cerebral palsy and epilepsy in VLBWIs. IMPACT: Very-low-birth-weight infants (VLBWIs) show divergent neurodevelopmental outcomes from age 3 to 6 years. A deep longitudinal study depicts the dynamic change in neurodevelopmental profiles of VLBWIs from age 3 to 6 years. Perinatal brain injury is associated with developmental delay, cerebral palsy and epilepsy, but not with ASD or ADHD at age 6 years.

The clinical and genetic landscape of early-onset thrombophilia in Japan.

OBJECTIVES: To determine the optimal management for early-onset thrombophilia (EOT), the genetic and clinical features of protein C (PC)-, protein S (PS)-, or antithrombin (AT)-deficient patients of ≤20 years of age were studied in Japan. METHODS/RESULTS: Clinical and genetic information of all genetically diagnosed cases was collected through the prospective, retrospective study, and literature review. One-hundred-one patients had PC (n = 55), PS (n = 29), or AT deficiency (n = 18). One overlapping case had PC- and PS-monoallelic variant. Fifty-five PC-deficient patients (54%) had 26 monoallelic or 29 biallelic variant(s), and 29 (29%) PS-deficient patients had 20 monoallelic or nine biallelic variant(s). None of the patients had AT-biallelic variants. The frequent low-risk allele p.K193del (PC-Tottori) was found in five patients with monoallelic (19%) but not 29 with biallelic variant(s). The most common low-risk allele p.K196E (PS-Tokushima) was found in five with monoallelic (25%) and six with biallelic variant(s) (67%). One exceptional de novo PC variant was found in 32 families with EOT. Only five parents had a history of thromboembolism. Thrombosis concurrently developed in three mother-newborn pairs (two PC deficiency and one AT deficiency). The prospective cohort revealed the outcomes of 35 patients: three deaths with PC deficiency and 20 complication-free survivors. Neurological complications were more frequently found in patients with PC-biallelic variants than those with PC-, PS-, or AT-monoallelic variants (73% vs. 24%, p = .019). CONCLUSIONS: We demonstrate the need for elective screening for EOT targeting PC deficiency in Japan. Early prenatal diagnosis of PC deficiency in mother-infant pairs may prevent perinatal thrombosis in them.

Critical diseases in neonates after discharge home from birth hospital: A retrospective study from a tertiary hospital in Japan.

INTRODUCTION: To establish actionable neonatal screening during the first month of life, we investigated critical diseases in seemingly healthy newborns discharged from birth hospitals. METHODS: This retrospective study enrolled previously healthy full-term infants who visited our hospital, a tertiary hospital in Japan, from home between 5 and 28 days after birth from 2009 to 2018. Infants with known perinatal or congenital diseases, positive newborn screening results, or accidental injuries were excluded. Data were collected from electronic medical records, including principal diagnosis, clinical details, and prognosis at 18 months of age. RESULTS: Ninety-seven (58 %) of 168 eligible neonates were admitted to the hospital, and 71 (42 %) were not. The median admission rate in patients with disease onset at ≤14 days after birth (80 %) was significantly higher than that in patients with disease onset at ≥15 days (42 %). Among 45 patients who received intensive medical care, 5 died and 10 developed neurodevelopmental sequelae. Four of 5 patients died by 100 days. Among 25 diseases treated in intensive care unit, 17 (68 %) diseases had a prevalence of <1 per 2000 live births. The commonly used diagnostic methods were imaging (n = 58, 35 %) and physical examination (n = 34, 20 %). CONCLUSION: Critical diseases due to rare and heterogeneous causes in ostensibly healthy newborns occurred predominantly in the first two weeks of life. Optimal newborn screening and health check-up protocols may benefit from the wide spectrum of life-threatening diseases occurring in home after birth.

Changing risk factors for postpartum depression in mothers admitted to a perinatal center.

BACKGROUND: The Edinburgh postnatal depression scale (EPDS) is commonly used in screening for major postpartum depression (PPD). We explored the clinical factors associated with score changes. METHODS: Mothers (n=1,287) who delivered a single live-born infant in Kokura Medical Center in Japan during 2018-2019 were analyzed. The EPDS-Japanese version was conducted at the first and fourth weeks after childbirth. Scores of ≥9 were considered to indicate an increased risk of PPD. RESULTS: The scores improved during the four-week period (5.03±0.12 to 3.79±0.10). Primiparity, Cesarean section (CS), and a low Apgar score were identified as initial risk factors, however, primiparity remained in the multivariate analysis (aOR 2.02, 95% CI 1.37-2.97). Age ≥35 years was associated with worsened scores (aOR 1.88, 95%CI 1.01-3.51), but CS improved (aOR 0.38, 95%CI 0.21-0.70). Primiparity, CS, and neonatal respiratory support were the initial risk factors, while infant anomaly was a late risk factor in mothers whose infants were admitted to the neonatal intensive care unit (NICU) (aOR 3.35, 95%CI 1.31-8.56). In mothers of infants with an NICU stay of ≥4 weeks, infant anomaly was associated with worsened scores (aOR 6.61, 95%CI 1.11-39.3), while respiratory support was associated with improved scores (aOR 0.09, 95%CI 0.01-0.65). Twenty-six mothrs with worsened scores received psychiatric support; three developed PPD. Two of the three were ≥35 years of age, neither of their infants had anomalies. CONCLUSION: Maternal aging and infant anomaly were risk factors for PPD. PPD occurred in mothers with worsened EPDS scores after mental care. Puerperants with worsening risk factors should be targeted to control PPD.

Effectiveness of umbilical culture for surveillance of methicillin-resistant Staphylococcus aureus among neonates admitted to neonatal intensive care units.

To compare the culture sensitivities of MRSA detection, we collected 988 paired umbilical and nasal cultures from screened neonates. MRSA positivity rates were 79.1% from umbilicus and 41.9% from nares (P = .01). The umbilicus was a more useful culture site than the nares for surveillance of MRSA among neonates upon admission.

No association between prenatal lead exposure and neurodevelopment during early childhood in the Japan Environment and Children's Study.

Compared with the relatively well-investigated effects of childhood exposure to lead on neurocognitive deficits, those of prenatal exposure remain relatively inconclusive. We aimed to investigate the association between prenatal blood lead levels and neurodevelopmental delay during the first three years of life. From a prospective cohort of the Japan Environment and Children's Study, we analyzed a total of 80,759 children. The exposure factors were prenatal lead concentrations measured from maternal whole blood in the second/third trimesters and umbilical cord blood at birth. Neurodevelopment was assessed at 6, 12, 18, 24, 30, and 36 months old using a screening tool, the Ages and Stages Questionnaires, third edition (ASQ). The outcome measures were any suspected neurodevelopmental delay (sNDD) identified via the ASQ during the first (sNDD-1Y), second (sNDD-2Y), and third (sNDD-3Y) years of life. sNDD-1Y, 2Y, and 3Y were identified in 18.0%, 16.2%, and 17.2% of children, respectively. The geometric means of blood lead concentration in this study were much lower (0.62 µg/dL in maternal blood and 0.50 µg/dL in cord blood) than previously investigated levels. Multivariable regression models revealed that there were no associations between maternal blood lead and sNDD-1Y and 2Y and between cord blood lead and sNDD-1Y, 2Y, and 3Y. Although a higher maternal blood lead was associated with a reduced risk of sNDD-3Y (adjusted relative risk: 0.84, 95% confidence interval 0.75-0.94, per 1 increase in common logarithm of lead concentration), there were no dose-response relationships in the analysis using quintiles of lead concentrations. Using a large-scale data set, the present study demonstrated no convincing evidence for an inverse association between levels of prenatal blood lead and neurodevelopment in early childhood. Longitudinal measurements of prenatal and postnatal lead levels are needed to understand the relationship between lead exposure and neurocognitive development.

Clinical outcomes of pulmonary agenesis: A systematic review of the literature.

INTRODUCTION: Pulmonary agenesis is a complete absence of the pulmonary parenchyma, airways, and vasculature unilaterally or bilaterally. Although bilateral cases are lethal, the outcome of unilateral cases remains not well described. We performed a comprehensive literature review to assess the clinical features of pulmonary agenesis. METHODS: Four database sources were searched on October 10, 2021 and two cases were included from our institution. Studies related to the clinical impact of comorbidity and intervention on the survival outcome in pulmonary agenesis were included for full-text review. RESULTS: We identified 259 patients-with right-sided (59%), left-sided (34%), and bilateral agenesis (7%)-among 195 articles and our two cases. Additional anomalies included cardiovascular (40%), skeletal (30%), gastrointestinal (20%), tracheal (20%: all stenoses), and genitourinary (14%) anomalies. Fifty-seven (24%) individuals in unilateral pulmonary agenesis had isolated disease. Outcomes related to survival were not uniformly reported, but the 2-year overall survival rate of unilateral agenesis was 62% and no subsequent death was reported until 13 years of age. The right-sided agenesis was more frequently associated with tracheal stenosis (27% vs. 11%, p = 0.003) than the left-sided disease. A multivariable analysis indicated that tracheal stenosis (hazard ratio [HR]: 2.2, 95% confidence interval [CI]: 1.3-4.1, p = 0.003) and gastrointestinal anomalies (HR: 2.0, 95% CI: 1.1-3.3, p = 0.010) were prognostic factors for mortality. CONCLUSIONS: The poor prognostic factors were tracheal stenosis, right agenesis, and gastrointestinal anomalies. Treatment for these comorbidities is a key point for improving the survival of unilateral pulmonary agenesis.

Lung to thorax transverse area ratio as a predictor of neurodevelopmental outcomes in fetuses with congenital diaphragmatic hernia.

INTRODUCTION: Infants with congenital diaphragmatic hernia (CDH) are at risk of neurodevelopmental disabilities. This study aimed to investigate the association between lung to thorax transverse area ratio (LTR) and neurodevelopmental outcomes at 3 years of age in fetuses with CDH. METHODS: We performed a retrospective study of infants with prenatally diagnosed isolated left-sided CDH born in Kyushu University Hospital between 2008 and 2016. We examined the association between prenatal ultrasound findings including LTR and development quotient (DQ) at 36 to 42 months of chronological age. RESULTS: We identified 34 live-born fetuses with isolated left-sided CDH, of which 30 survived and four died before discharge. The median LTR in the survivors was higher than in the non-survivors (p < 0.01). Among the survivors, 26 had available data on LTR (median 0.12, range 0.08-0.18) and overall DQ at 3 years of age (93, 61-112). Their median gestational age and birth weight were 37.6 (range 34.4-39.1) weeks and 2716 (2.256-3494) grams, respectively. There was no significant difference in overall DQ scores between the two groups divided according to the median LTR values (p = 0.62). LTR values were not associated with overall DQ scores after adjusting for gestational age (p = 0.39). In addition, no association was observed between LTR values and any subscale DQ scores. CONCLUSION: In fetuses with isolated left-sided CDH, prenatal LTR predicts the mortality but not neurodevelopmental outcomes at 3 years of age.

Optimal Teicoplanin Dosing Regimen in Neonates and Children Developed by Leveraging Real-World Clinical Information.

BACKGROUND: Teicoplanin is a glycopeptide antibiotic used for the treatment of methicillin-resistant Staphylococcus aureus infections. To ensure successful target attainment, therapeutic drug monitoring-informed dosage adjustment is recommended. However, it relies on the experience of the clinician and the frequency of drug measurements. This study aimed to design a new optimal dosing regimen of teicoplanin with a maintenance dosing strategy for neonates and children based on their physiological characteristics. METHODS: Data from teicoplanin-treated patients (n = 214) were collected from electronic medical records. Covariate analyses were performed using population pharmacokinetic (PK) modeling with 399 serum teicoplanin concentrations from 48 neonates and 166 children. Multiple PK simulations were conducted to explore optimal dosing regimens that would allow control of the trough concentration to the target of 15-30 mg/L quicker than the current standard regimen. RESULTS: Allometrically scaled body weight, postmenstrual age (PMA), renal function, and serum albumin were implemented as substantial covariates for teicoplanin clearance in a two-compartment PK model. Covariate analyses and comprehensive simulation assessments recommended the following modifications to the current regimen: (1) decreased dose for premature babies (PMA ≤28 weeks), (2) decreased dose for children with renal dysfunction, and (3) increased dose for children (0.5-11 years) with an estimated glomerular filtration rate of ≥90 mL/min/1.73 m2. CONCLUSIONS: This study leverages real-world clinical information and proposes new optimal dosing regimens for teicoplanin in neonates and children through PK modeling and simulation analyses, taking into account the age, including PMA, and renal function of patients.

Serum erythroferrone levels during the first month of life in premature infants.

OBJECTIVE: To examine erythroferrone (ERFE)-hepcidin iron regulation in premature infants under intensive care at risk of iron metabolic disorders. STUDY DESIGN: A retrospective cohort recruited 31 infants with a birth weight of <1500 g hospitalized in a tertiary center. Their hematological status was measured at birth and 2 and 4 weeks of life. RESULTS: ERFE was positively correlated with the reticulocyte hemoglobin content at 2 (r2 = 0.2374) and 4 weeks (r2 = 0.6005). An assumed negative correlation between ERFE and hepcidin was not determined during the neonatal period. Hepcidin was positively correlated with the leukocyte count (r2 = 0.3089) and ferritin (r2 = 0.7476) at birth and C-reactive protein (r2 = 0.3591) at 2 weeks and negatively correlated with the reticulocyte count (r2 = 0.2887) at 4 weeks. CONCLUSION: The vulnerability of the ERFE-hepcidin pathway within 4 weeks may contribute to iron imbalance in premature infants.

Neurodevelopmental Outcomes of High-Risk Preterm Infants: A Prospective Study in Japan.

OBJECTIVES: To determine the neurodevelopmental outcomes of very-low-birth-weight infants (VLBWIs, birth weight <1,500 g) after 9 years of follow-up. METHODS: This study prospectively recruited 224 VLBWIs born from 2003 to 2009 in Kyushu University Hospital, Japan. Comorbidities of neurocognitive impairment, epilepsy, and autism spectrum disorder or attention-deficit hyperactivity disorder (ASD/ADHD) were assessed at age 3, 6, and 9 years. RESULTS: Neurodevelopmental profiles were obtained from 185 (83%), 150 (67%), and 119 (53%) participants at age 3, 6, and 9 years, respectively. At age 9 years, 25 (21%) VLBWIs showed intelligence quotient (IQ) <70, 11 (9%) developed epilepsy, and 14 (12%) had a diagnosis of ASD/ADHD. The prevalence of epilepsy was higher in children with an IQ <70 at age 9 years than in those with an IQ ≥70 (44% vs 0%). In contrast, ASD/ADHD appeared at similar frequencies in children with an IQ <70 (16%) and ≥70 (11%). Perinatal complications and severe brain lesions on MRI were considered common perinatal risks for developmental delay and epilepsy but not for ASD/ADHD. Male sex was identified as a unique risk factor for ASD/ADHD. CONCLUSION: These data suggest that VLBWIs showed a higher prevalence of developmental delay, epilepsy, and ASD/ADHD at age 9 years than the general population. Distinct mechanisms might be involved in the pathogenic process of ASD/ADHD from those of developmental delay and epilepsy.

Physical growth and neurodevelopment during the first year of life: a cohort study of the Japan Environment and Children's Study.

BACKGROUND: The association between a slower physical growth and poorer neurodevelopment has been established in infants born preterm or small for gestational age. However, this association is inconsistent in term-born infants, and detailed investigations in infancy, when intervention is most beneficial for improving outcomes, are lacking. We therefore examined this association separately by sex during the first year of life in term-born infants. METHODS: Using data collected until children reached 12 months old in an ongoing prospective cohort of the Japan Environment and Children's Study, we analyzed 44,264 boys and 42,541 girls with singleton term-birth. The exposure variables were conditional variables that disentangle linear growth from weight gain relative to linear growth, calculated from the length and weight at birth and 4, 7 and 10 months old. Neurodevelopmental delay was identified using the Japanese-translated version of Ages & Stages Questionnaires, third edition. RESULTS: A reduced risk of neurodevelopmental delay at 6 months old was observed in children with a higher birth weight (adjusted relative risks [aRRs]: 0.91 and 0.93, 95 % confidence intervals [95 % CIs]: 0.87-0.96 and 0.88-0.98 in boys and girls, respectively) and increased linear growth between 0 and 4 months old (aRRs: 0.85 and 0.87, 95 % CIs: 0.82-0.88 and 0.83-0.91 in boys and girls, respectively). A reduced risk at 12 months was found in children with an increased linear growth between 0 and 4 months (aRRs: 0.92 and 0.90, 95 % CIs: 0.87-0.98 and 0.84-0.96 in boys and girls, respectively), boys with an increased relative weight gain between 0 and 4 months (aRR: 0.90, 95 % CI: 0.84-0.97), and girls with a higher birth weight (aRR: 0.89, 95 % CI: 0.83-0.96). CONCLUSIONS: These results suggest that a slow physical growth by four months old may be a predictor of neurodevelopmental delay during infancy.

Survival outcomes of very low birth weight infants with trisomy 18.

Trisomy 18 (T18) is one of the most commonly diagnosed aneuploidies leading to poor survival outcome. However, little is known about the dual risk of T18 and very low birth weight (VLBW, weighing <1500 g at birth). We aimed to investigate the survival and clinical features of VLBW infants with T18. In this observational cohort study, infants with T18 admitted to the neonatal intensive care unit in Kyushu University Hospital from 2000 to 2019 were eligible. Among 30 infants with T18 who were enrolled as study participants, 11 (37%) were born with VLBW. VLBW infants had lower gestational age (34.4 vs. 39.4 weeks, p < 0.01) and a higher incidence of esophageal atresia (64% vs. 11%, p < 0.01) than non-VLBW infants. The proportions of patients who underwent any surgery (55% vs. 5%, p < 0.01) and positive pressure ventilation (82% vs. 32%, p = 0.02) were higher in VLBW than non-VLBW infants. One-year overall survival rate (45% vs. 26%, p = 0.32 by log-rank test) did not differ between the two groups. In conclusion, being born at VLBW may not be fatal for infants with T18 undergoing active interventions.

Clinical Impact of Heritable Thrombophilia on Neonatal-Onset Thromboembolism: A Nationwide Study in Japan.

OBJECTIVE: To clarify the incidence and genetic risk of neonatal-thromboembolism, we conducted a nationwide study exploring the impact of thrombophilia on neonatal-thromboembolism in Japan. STUDY DESIGN: A questionnaire survey was conducted for perinatal centers in Japan, focusing on the clinical expression, genotype, treatment, and outcome of patients who developed thromboembolism within 28 days of birth from 2014 to 2018. RESULTS: The estimated incidence of neonatal-thromboembolism was 0.39 cases per 10 000 live births. Intracranial lesions and purpura fulminans occurred in 66 and 5 of 77 patients, respectively. Fifty-eight (75.3%) infants presented within 3 days after birth. Four (5.2%) died, and 14 (18.2%) survived with disability. At the diagnosis, <20% plasma activity of protein C was noted in 16 infants, protein S (in 2), and antithrombin (in 1). Thirteen genetic tests identified 4 biallelic and 5 monoallelic protein C-variants but no protein S- or antithrombin-variants. Protein C-variants had purpura fulminans (P < .01), ocular bleeding (P < .01), positive-family history (P = .01), and death or disability (P = .03) more frequently than others. Protein C-variants were independently associated with disability (OR 5.74, 95% CI 1.16-28.4, P = .03) but not death. Four biallelic variants had serious thrombotic complications of neurologic disability, blindness, and/or amputation. Three monoallelic variants survived without complications. The only protein C-variant death was an extremely preterm heterozygote infant. CONCLUSIONS: Monoallelic protein C-variants had a higher incidence of neonatal-thromboembolism than biallelic variants. Thrombophilia genetic testing should be performed in the setting of neonatal-thromboembolism and low protein C to identify the underlying genetic defect.

Study protocol for a multicentre, open-label, single-arm phase I/II trial to evaluate the safety and efficacy of ripasudil 0.4% eye drops for retinopathy of prematurity.

INTRODUCTION: Retinopathy of prematurity (ROP) is a vascular proliferative disorder that occurs in preterm infants. Existing treatments are only indicated in severe ROP cases due to the high invasiveness and the potential risk of irreversible side effects. We previously elucidated that ripasudil, a selective inhibitor of the Rho-associated protein kinase, has the ability to inhibit abnormal retinal neovascularisation in animal models. In addition, ripasudil eye drops (Glanatec ophthalmic solution 0.4%) have been already used for the treatment of glaucoma. Since eye drop therapy is less invasive, early intervention for ROP is possible. The purpose of this phase I/II trial is to evaluate the safety and efficacy of ripasudil eye drops for preterm infants with ROP. METHODS AND ANALYSIS: This is a multicentre, open-label, single-arm phase I/II trial. To evaluate the safety and efficacy of ripasudil as much as possible, ripasudil will be administered to all enrolled preterm infants with zone I/II, stage 1, or worse ROP. The safety and efficacy of ripasudil in treated patients will be assessed in comparison to a historical control group. Because this is the first trial of ripasudil in preterm infants, a dose-escalation study (once daily for 1 week, then two times per day for 2 weeks) will be conducted in phase I. After obtaining approval from the independent data and safety monitoring board to continue the trial after the completion of phase I, phase II will be conducted. In phase II, ripasudil eye drops will be administered two times per day for 12 weeks. The primary endpoint in phase II is also safety. Efficacy and pharmacokinetics will be evaluated as secondary endpoints. ETHICS AND DISSEMINATION: This study protocol was approved by the institutional review board at each of the participating centres. Data will be presented at international conferences and published in peer-reviewed journals. TRIAL REGISTRATION NUMBERS: NCT04621136 and jRCT2071200047.

Trends in Bronchopulmonary Dysplasia Among Extremely Preterm Infants in Japan, 2003-2016.

OBJECTIVE: To investigate recent trends in bronchopulmonary dysplasia (BPD) and its risk factors among extremely preterm infants. STUDY DESIGN: Demographic and clinical data were reviewed for 19 370 infants born at 22-27 weeks of gestation registered in the affiliated hospitals of the Neonatal Research Network of Japan between 2003 and 2016. We investigated the overall survival and prevalence of bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age and risk factors for developing BPD among the survivors. RESULTS: Among 19 370 infants, 2244 (11.6%) died by 36 weeks' postmenstrual age. The mortality rate decreased from 19.0% (99% CI, 15.7%-22.8%) in 2003 to 8.0% (99% CI, 6.2%-10.3%) in 2016. Among 17 126 survivors, BPD developed in 7792 (45.5%) infants, and its proportion significantly increased from 41.4% (99% CI, 36.5%-46.4%) in 2003 to 52.0% (99% CI, 48.2%-55.9%) in 2016. A multivariable analysis of the survivors showed a positive association of BPD with ≥4 weeks' supplemental oxygen or invasive ventilation, birth weight <750 g, small for gestational age, ≥4 weeks' noninvasive positive pressure ventilation, chorioamnionitis, <26 weeks' gestational age, <20 cases per year of center patient volume, or treated patent ductus arteriosus. Although the median duration of invasive ventilation was shortened, the proportions of factors associated adversely with BPD generally showed increasing trends over time. CONCLUSIONS: The mortality rate of extremely preterm infants has decreased, but the rate of BPD has increased in survivors between 2003 and 2016. Despite the decreasing duration of invasive ventilation over time, increasing rates of BPD suggest that differences in the patient population or other management strategies influence the development of BPD.