Survey of enteral feeding of preterm infants and the human milk bank in Japan.

BACKGROUND: In Japan, the first human milk bank (HMB) was established in 2017, which changed the practice of enteral feeding in neonatal care. This study investigated the practice of enteral feeding of preterm infants after the establishment of the HMB in Japan and examined related future issues. METHODS: A survey on enteral feeding and the use of the HMB was conducted in 251 neonatal intensive care units (NICUs) from December 2020 to February 2021. RESULTS: The response rate was 61%. The ideal times to start enteral feeding for extremely-low-birthweight infants (ELBWI) and very-low-birthweight infants (VLBWI) were within 24 h after birth in approximately 59% and 62% of NICUs, however, only 30% and 46% could do so, respectively. Artificial nutrition was used to initiate enteral feeding for ELBWIs and VLBWIs in in 24% and 56% of NICUs, respectively. Of the NICUs, 92% considered the HMB "necessary" or "rather necessary". Fifty-five percent wanted to use the HMB but could not. The major reasons for this were (1) difficulty in paying the annual membership fee, (2) difficulty obtaining approval from the NICU, and (3) complexity in using the facility. The indications for using and discontinuation of use of donor milk varied among the NICUs. Only in 17%, milk expression was within 1h after delivery. CONCLUSIONS: Compared with before the establishment of the HMB, NICUs are currently more willing to start enteral feeding for preterm infants earlier. However, the implementation of enteral feeding appears to be challenging. Issues related to the HMB highlighted by the responses need to be addressed. Additionally, guidelines for using donor milk should be established.

Breast-feeding rate comparison by parity and delivery age in Japan.

BACKGROUND: To examine the effects of maternal age on breast-feeding, we classified mothers who delivered vaginally aged 20-42 into 1-year age groups and investigated breast-feeding states. We also studied differences between primiparas and multiparas in breast-feeding. METHODS: The subjects were 2,605 primipara mothers (age at delivery ranged from 16to 45 years; the gestational age of their infants ranged from 37 to 42 weeks, birthweight ranged from 2,501 to 4,300 g) and 3,261 multipara mothers (age 18-45 years; the gestational age of their infants ranged from 37-42 weeks, and their birthweight ranged from 2,502-4,726 g) at 12 baby-friendly hospitals in Japan. RESULTS: The percentage of infants exclusively breast-fed at 1 week and 1 month after birth in the primipara mothers was 80% among mothers in their 20s but lower than 60% among mothers aged above 35. On the other hand, the percentage of infants exclusively breast-fed in the multipara mothers was almost 90% among mothers in their 20s and remained at 70% or over among mothers in their 40s. The percentage of infants exclusively breast-fed was significantly higher in the multipara mothers than in the primipara mothers in many age groups at both 1 week and 1 month of age. CONCLUSIONS: The percentage of infants exclusively breast-fed rate decreased as the maternal age increased. We found that multipara mothers can breast-feed even in their 40s, but primipara mothers may encounter difficulty breast-feeding at ages above 35. Our results suggest a need to consider not only their age but number of children, i.e., breast-feeding experience, to provide effective support to breast-feeding mothers.

Antenatal Administration of Betamethasone Contributes to Intimal Thickening of the Rat Ductus Arteriosus.

BACKGROUND: Antenatal betamethasone (BMZ) is a standard therapy for reducing respiratory distress syndrome in preterm infants. Recently, some reports have indicated that BMZ promotes ductus arteriosus (DA) closure. DA closure requires morphological remodeling; that is, intimal thickening (IT) formation; however, the role of BMZ in IT formation has not yet been reported. Methods and Results: First, DNA microarray analysis using smooth muscle cells (SMCs) of rat preterm DA on gestational day 20 (pDASMCs) stimulated with BMZ was performed. Among 58,717 probe sets, ADP-ribosyltransferase 3 (Art3) was markedly increased by BMZ stimulation. Quantitative reverse transcription polymerase chain reaction (RT-PCR) confirmed the BMZ-induced increase of Art3 in pDASMCs, but not in aortic SMCs. Immunocytochemistry showed that BMZ stimulation increased lamellipodia formation. BMZ significantly increased total paxillin protein expression and the ratio of phosphorylated to total paxillin. A scratch assay demonstrated that BMZ stimulation promoted pDASMC migration, which was attenuated byArt3-targeted siRNAs transfection. pDASMC proliferation was not promoted by BMZ, which was analyzed by a 5'-bromo-2'-deoxyuridine (BrdU) assay. Whether BMZ increased IT formation in vivo was examined. BMZ or saline was administered intravenously to maternal rats on gestational days 18 and 19, and DA tissues were obtained on gestational day 20. The ratio of IT to tunica media was significantly higher in the BMZ-treated group. CONCLUSIONS: These data suggest that antenatal BMZ administration promotes DA IT through Art3-mediated DASMC migration.

Urinary ß2-microglobulin and bronchopulmonary dysplasia: Trends in preterm infants.

BACKGROUND: The developmental process of bronchopulmonary dysplasia (BPD) is not identical between very preterm infants born small for gestational age (SGA) and those born appropriate for gestational age (AGA). In this study, we compared the pattern of the inflammatory response in infants of each group, by measuring urinary ß2-microglobulin (Uß2M) as an alternative, concise, and less-invasive biomarker. METHODS: Uß2M and clinical details were examined at birth and at 4 weeks of age in 146 very preterm infants. RESULTS: Of the 57 infants diagnosed with BPD, 18 were SGA, and 39 were AGA. Uß2M at birth was significantly lower in SGA BPD infants than in AGA BPD infants, but it increased with time. The prevalence of chorioamnionitis (CAM) was significantly lower in SGA BPD infants than in AGA BPD infants, while that of pregnancy-induced hypertension was the opposite. CONCLUSIONS: Exposure to prenatal factors other than CAM may sensitize fetal lungs to become vulnerable to postnatal inflammation in very preterm SGA infants with BPD.

Glutamate Promotes Contraction of the Rat Ductus Arteriosus.

BACKGROUND: Extremely preterm infants frequently have patent ductus arteriosus (PDA). Recent recommendations include immediately beginning amino acid supplementation in extremely preterm infants. However, the effect of amino acids on closure of the ductus arteriosus (DA) remains unknown.Methods and Results:Aminogram results in human neonates at day 2 revealed that the plasma glutamate concentration was significantly lower in extremely preterm infants (<28 weeks' gestation) with PDA than in those without PDA and relatively mature preterm infants (28-29 weeks gestation). To investigate the effect of glutamate on DA closure, glutamate receptor expression in fetal rats was examined and it was found that the glutamate inotropic receptor, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) type subunit 1 (GluR1), mRNA was highly expressed in the DA compared to the aorta on gestational day 19 (preterm) and gestational day 21 (term). GluR1 proteins were co-localized with tyrosine hydroxylase-positive autonomic nerve terminals in the rat and human DA. Intraperitoneal administration of glutamate increased noradrenaline production in the rat DA. A whole-body freezing method demonstrated that glutamate administration induced DA contraction in both preterm (gestational day 20) and term rat fetuses. Glutamate-induced DA contraction was attenuated by the calcium-sensitive GluR receptor antagonist, NASPM, or the adrenergic receptor α1 blocker, prazosin. CONCLUSIONS: These data suggest that glutamate induces DA contraction through GluR-mediated noradrenaline production. Supplementation of glutamate might help to prevent PDA in extremely preterm infants. (Circ J 2016; 80: 2388-2396).

Efficacy of Cranial Orthosis for Plagiocephaly Based on 2D and 3D Evaluation.

Background With the advent of cranial orthoses as therapeutic medical devices for the treatment of severe positional head deformities in Japan, an increasing number of patients are being treated with them. However, assessing the effectiveness of a treatment is often difficult due to the use of different metrics. This study aimed to evaluate the effectiveness of cranial orthoses for deformational plagiocephaly using two- (2D) and three-dimensional (3D) evaluation metrics. Methods We conducted a retrospective study of infant patients with deformational plagiocephaly who underwent cranial orthosis treatment. We evaluated the severity of deformational plagiocephaly using cranial asymmetry (CA) and the cranial vault asymmetry index (CVAI) as 2D metrics, and anterior and posterior symmetry ratios as 3D metrics. The patients were divided into 24 subgroups based on the initial severity of each outcome and their age at the start of treatment. We analyzed the changes in outcomes and correlations within improvements across the age and severity categories. Results Overall, 1,038 infants were included in this study. The mean CA, CVAI, and anterior and posterior symmetry ratios improved significantly after cranial orthosis treatment. The improvement in each score was greater in patients with more severe initial deformities and in those who underwent treatment at a younger age. Conclusion Cranial orthosis treatment was effective in correcting deformational plagiocephaly in infants, as demonstrated by improvements in both 2D and 3D metrics. Patients with more severe initial deformities and those who underwent treatment at a younger age showed greater improvement.

Immune response to Haemophilus influenzae type b conjugate vaccine in preterm infants.

BACKGROUND: Haemophilus influenzae type b (Hib) vaccine became available for use in Japan in December 2008. The aim of the present study was to evaluate the immunogenicity of Hib vaccine in Japanese preterm infants. METHODS: Serum samples were obtained from 54 preterm infants before the first vaccination and 1 month after the third. Anti-polyribosylribitol phosphate (PRP) antibodies were measured using an enzyme-linked immunosorbent assay method. Antibody positivity was defined as levels >1 µg/mL. RESULTS: Of the 54 preterm infants, 46 (85.2%) achieved antibody levels >1 µg/mL. This compares with the 92.4% reported in full-term infants. The antibody seroconversion rate of infants starting vaccination at 2 months of age was close to being significantly lower than when vaccination was started at 3 months of age (P= 0.060). In addition, the percentage of infants achieving a positive response in the group with a history of antenatal steroid exposure was significantly higher than in those not exposed (P= 0.046). Thus, risk factors for lower Hib antibody concentrations after three doses of vaccine were age at first vaccination and lack of use of antenatal steroids. CONCLUSIONS: There is a possibility that perinatal factors and the environment unique to preterm infants are related to their lower antibody positivity rates compared to full-term infants. It may therefore be preferable to modify the proposed immunization schedule.

Urinary ß2-microglobulin in very preterm neonates with chorioamnionitis.

It is important to identify premature infants with prenatal inflammation as it contributes to short- and long-term complications. Our object was to study how prenatal inflammation affects the urinary ß(2)-microglobulin (ß(2)-MG) level. Preterm neonates were divided based on the presence of chorioamnionitis (CAM) into the CAM (n = 100) and non-CAM groups (n = 117). These were further subdivided into five groups each: 30 preterm neonates of 23-26; 42 neonates of 27-28; 54 neonates of 29-30; 51 neonates of 31-32; and 40 neonates of 33-34 weeks' gestation. The urinary ß(2)-MG level within 48 h of birth was significantly higher in the CAM group than in the non-CAM group among the neonates of 23-26 weeks' gestation (18.3 ± 6.9 vs 10.0 ± 5.6 × 10(4) µg/gCr, p = 0.0018) and the neonates of 27-28 weeks' gestation (16.2 ± 10.8 vs 8.8 ± 3.3 × 10(4) µg/gCr, p = 0.0101). However, there was no difference in urinary ß(2)-MG level between the CAM and the non-CAM group among the neonates ≥ 29 weeks 'gestation. Moreover, the elevated urinary ß(2)-MG level in the neonates ≤ 28 weeks ' gestation with CAM had disappeared by 1 week after birth. The reasons for the increase in urinary ß(2)-MG level within 48 h of birth in very preterm neonates (≤ 28 weeks' gestation) with CAM are believed to be not only prematurity, but also prenatal inflammation. It is suggested that the urinary ß(2)-MG level during the early postnatal period can identify prenatal inflammation.

Early discharge from a neonatal intensive care unit and rates of readmission.

BACKGROUND: Increasing admissions to neonatal intensive care units (NICUs) demand early discharge from the units. Our hospital aims to early discharge patients who meet the following requirements: they are able to regulate body temperature; neither apnea nor bradycardia is observed; and bodyweight increases with lactation. We studied the real state of this strategy. METHODS: We looked at postmenstrual age, bodyweight, complication at the time of discharge and the readmission rate in 609 patients with gestational age of less than 34 weeks, who were discharged from our NICU between January 2000 and March 2008. RESULTS: The postmenstrual age and bodyweight at discharge decreased with the increase of gestational age. This tendency was stronger in cases with gestational age of less than 26 weeks. A comparison was made between two patient groups with a gestational age of less than 26 weeks and with the age of 26 weeks or longer. Many patients with a gestational age of less than 26 weeks suffered frequently from complications and were on home oxygen therapy. The readmission rates within 3 months and 1 year of NICU discharge were 10.4% and 26.9% in patients with gestational age between 22 and 25 weeks, respectively, while those rates were 2.8% and 7.4% in patients with gestational weeks of 26 to 34, respectively. CONCLUSION: The postmenstrual age and bodyweight at NICU discharge decreased in inverse proportion to gestational age, especially less than 26 weeks. Our requirements for early discharge were verified by the readmission rate in this investigation.

Severity of chorioamnionitis and neonatal outcome.

AIM: The aim of this study is to elucidate whether the stage of chorioamnionitis is or is not associated with the development of neonatal diseases. MATERIAL & METHODS: We reviewed the neonatal intensive care unit discharge files and placental pathology reports of 302 preterm infants. The presence of various stages of chorioamnionitis as well as absence of an association with chorioamnionitis (non-chorioamnionitis) were compared among neonatal diseases. RESULTS: Preterm infants were grouped according to three stages of chorioamnionitis or the absence of an association with chorioamnionitis. Gestational age differed significantly between these groups. Before controlling for gestational age, the chorioamnionitis stage was significantly higher among infants with chronic lung disease, retinopathy of prematurity and intraventricular hemorrhage than in infants without these diseases. On the other hand, the chorioamnionitis stage was lower in infants with respiratory distress syndrome than without. After controlling for gestational age, the stage of chorioamnionitis was significantly lower in infants with respiratory distress syndrome than in infants without respiratory distress syndrome, whereas, significant differences were not detected between the presence and absence of chronic lung disease, retinopathy of prematurity and intraventricular hemorrhage. Furthermore, gestational age was a significant risk factor for chronic lung disease, respiratory distress syndrome, retinopathy of prematurity and intraventricular hemorrhage. CONCLUSIONS: We found no significant differences in stages of chorioamnionitis between infants with and without neonatal diseases except for respiratory distress syndrome. A significant inverse relationship was observed between the stage of chorioamnionitis and development of respiratory distress syndrome.

Soluble tumor necrosis factor receptor-1 in preterm infants with chronic lung disease.

BACKGROUND: It is clear that inflammation plays an important role in developing chronic lung disease in preterm infants. The purpose of the present study is to investigate changes of serum soluble tumor necrosis factor receptor-1 levels over time in infants with chronic lung disease. METHODS: The serum levels of soluble tumor necrosis factor receptor-1 were measured after delivery, and at 7, 14, 21 and 28 days of age in 10 infants with chronic lung disease and in 18 infants without chronic lung disease. RESULTS: The serum level of soluble tumor necrosis factor receptor-1 was significantly higher in infants with chronic lung disease than in infants without chronic lung disease after delivery. The differences between these two groups remained up to 28 days of age. CONCLUSION: Prenatal inflammation with persistence into postnatal inflammation may be involved in the onset of chronic lung disease.

Interleukin-6 inhibits early differentiation of ATDC5 chondrogenic progenitor cells.

Interleukin (IL)-6 is a causative agent of systemic juvenile idiopathic arthritis (sJIA), a chronic inflammatory disease complicated with severe growth impairment. Recent trials of anti-IL-6 receptor monoclonal antibody, tocilizumab, indicated that tocilizumab blocks IL-6/IL-6 receptor-mediated inflammation, and induces catch-up growth in children with sJIA. This study evaluates the effects of IL-6 on chondrogenesis by ATDC5 cells, a clonal murine chondrogenic cell line that provides an excellent model for studying endochondral ossification at growth plate. ATDC5 cells were examined for the expression of IL-6 receptor and gp130 by fluorescence-activated cell sorting analysis. Recombinant murine IL-6 was added to ATDC5 cultures to observe cell differentiation, using a quantitative RT-PCR for the chondrogenic differentiation markers type II collagen, aggrecan, and type X collagen. To block IL-6, the anti-mouse IL-6 receptor monoclonal antibody MR16-1 was added. As a result, the cells expressed IL-6 receptor and gp130. The expression of chondrogenic differentiation marker gene was reduced by IL-6, but this was abrogated by MR16-1. We conclude that IL-6 inhibits early chondrogenesis of ATDC5 cells suggesting that IL-6 may affect committed stem cells at a cellular level during chondrogenic differentiation of growth plate chondrocytes, and that IL-6 may be a cellular-level factor in growth impairment in sJIA.

Survey of psychological support for bereaved families in Japan.

BACKGROUND: The aim of the present study was to investigate the current conditions of psychological support for the families of children who died suddenly of disease or accident. METHODS: A questionnaire survey was conducted in 2415 medical facilities across the country that have at least 100 beds and are staffed by pediatricians. Of these, 981 facilities (40.6%) responded to the questionnaire. RESULTS: There were 653 infant deaths soon after admission in 254 facilities (25.9%). For pronouncement of death, approximately 43% of the pediatricians made no attempt to provide psychological support for the family members affected. In contrast, some 53% of the pediatricians did offer psychological support. In self-assessments, approximately 53% of the pediatricians stated that the support was 'not very satisfactory' or 'unsatisfactory', while only 28% considered that they were 'fully satisfied with the help being given'. Reasons for this response were appropriate specialized knowledge, and enough time for such tasks. The proportion of institutions that employed staff specializing in psychological support for families was only 7%. Approximately 83% of institutions without such specialist staff, however, acknowledged the need for them. The number of medical facilities that gave information regarding family support associations to bereaved families was very low (11%). CONCLUSION: Psychological support for families of children who died shortly after entering hospital cannot be characterized as satisfactory. The provision of grief care by family associations is desirable, and the cooperation of the institutions and family associations is important.

Whole blood interferon-gamma assay for tuberculosis in children in Japan.

BACKGROUND: Whole blood interferon-gamma assay QuantiFERON-TB2G (QFT-2G), which is a new specific method for diagnosing tuberculosis (TB), has been developed and used in the clinical field. The aim of the present study was to assess the usefulness of QFT-2G as an indicator, both for diagnosing childhood TB and for assessing therapeutic effectiveness. METHODS: The subjects were 61 children introduced to the TB outpatient department for the first time between June 2004 and March 2006. QFT-2G, the tuberculin test and chest computed tomography (CT) were performed for all patients. RESULTS: Ten patients having typical characteristics of primary tuberculosis (PTB) on chest CT, and diagnosed as having tubercle bacillus infections, all had positive reaction on QFT-2G. Of seven patients who had no abnormalities on diagnostic imaging but who reacted positively on QFT-2G, one developed TB later, and no TB was detected over the period of observation in 44 patients with negative QFT-2G at their first consultation. Moreover, four patients with non-tuberculous acid-fast bacilli in which Mycobacterium avium or Mycobacterium gordonae was detected had negative reaction on QFT-2G. In addition, all 10 patients with positive reactions on QFT-2G in whom the subsequent course of the disease was observed had decrease on QFT after treatment. CONCLUSIONS: QFT-2G is a powerful tool with a wide application both in diagnosis and in assessment of treatment effectiveness in PTB.

A case of fetal leukemia with intracranial hemorrhage and early-onset jaundice. Fetal leukemia with intracranial hemorrhage and jaundice.

We report a case of a neonate who was diagnosed as having congenital leukemia after presenting with an intracranial hemorrhage. The chief symptom was early-onset jaundice due to the hemorrhage. The intracranial hemorrhage and post-hemorrhage hydrocephalus advanced. In addition, the leukemia worsened leading to death at 14 days old. The possibility of leukemia, although rare, should be considered as a cause of intracranial hemorrhage in term babies.

Risk factors for nosocomial infection in the neonatal intensive care unit by the Japanese Nosocomial Infection Surveillance (JANIS).

We evaluated the infection risks in the neonatal intensive care unit (NICU) using data of NICU infection surveillance data. The subjects were 871 NICU babies, consisting of 465 boys and 406 girls, who were cared for between June 2002 and January 2003 in 7 medical institutions that employed NICU infection surveillance. Infections were defined according to the National Nosocomial Infection Surveillance (NNIS) System. Of the 58 babies with nosocomial infections, 15 had methicillin-resistant Staphylococcus aureus (MRSA) infection. Multiple logistic regression analysis demonstrated that the odds ratio for nosocomial infections was significantly related to gender, birth weight and the insertion of a central venous catheter (CVC). When the birth weight group of more than 1, 500 g was regarded as the reference, the odds ratio was 2.35 in the birth weight group of 1,000-1,499 g and 8.82 in the birth weight group of less than 1,000g. The odds ratio of the CVC (+) for nosocomial infection was 2.27. However, other devices including artificial ventilation, umbilical artery catheter, umbilical venous catheter, and urinary catheter were not significant risk factors. The incidence of MRSA infection rapidly increased from 0.3% in the birth weight group of more than 1,500 g to 2.1% in the birth weight group of 1,000-1,499 g, and to 11.1% in the birth weight group of less than 1,000g. When the birth weight group of more than 1,500 g was regarded as the reference, multiple logistic regression analysis demonstrated that the odds ratio was 7.25 in the birth weight group of 1,000-1,499 g and 42.88 in the birth weight group of less than 1,000g. These odds ratios were significantly higher than that in the reference group. However, the application of devices did not cause any significant differences in the odds ratio for MRSA infection.

Questionnaire study to Japanese SIDS families.

OBJECTIVES: To clarify the situation of the incidence of the sudden infant death syndrome (SIDS) in Japan to provide the basis for health administration training. METHOD: The questionnaire study about the circumstances and responses in discovering the death of a SIDS infant was carried out by the SIDS Family Association Japan. The bereaved parents were asked to reply as to whether or not the SIDS was the cause of their children's death, carried out a cross tabulation and a chi2 test of significance. RESULT: We found differences between SIDS and non-SIDS infants in respect to the place of death, the health condition up to death, the sleeping position at the time of death and room sharing. With regards to the responses on the death of a child, we found differences between the SIDS and non-SIDS infants in respect to whom the infant was in contact with at the time of death and especially with the responses of the paramedics. Other differences found were in respect to whether or not considerations were given to the family in informing them about procedures and treatment, in informing them of the procedures and medical information or to the family's feelings in advising an autopsy and whether or not a sufficient explanation was provided before the autopsy. CONCLUSION: To lighten the trauma suffered by a SIDS family, it is necessary that we pay adequate attention to giving consideration to the family through general informed consent including giving thoughtful consideration in advising an autopsy.

Postnatal changes of cytokines in premature infants with or without funisitis.

OBJECTIVE: Fetal inflammatory response syndrome (FIRS), which induces hypercytokinemia, is important for the outcomes of premature infants. It is necessary to focus on the fetal inflammatory environments. METHODS: A total of 37 premature infants (gestational age ≤32 weeks) were divided into three groups: (1) 15 without chorioamnionitis (CAM) and funisitis; C(-)F(-) group, (2) 15 with CAM but without funisitis; C(+)F(-) group and (3) 7 with CAM and funisitis; C(+)F(+) group. Blood interleukin (IL)-1ß, IL-6 and IL-8 levels were measured on day 0 (= in umbilical cord blood), 3, 7, 14, 21 and 28. RESULTS: (1) day 0: Cord blood concentrations of IL-1ß, IL-6 and IL-8 were significantly higher in the C(+)F(+) group than in the C(+)F(-) group and C(-)F(-) group. On the other hand, they were comparable between the C(+)F(-) group and C(-)F(-) group. (2) Days 3-28: elevated cytokines levels in the C(+)F(+) group with funisitis decreased on day 3 and later. CONCLUSIONS: We suggested that hypercytokinemia in the cord blood in premature infants were greatly related with funisitis. Diagnosis of funisitis would be important to find the premature infants who need to be managed their risk of FIRS. In addition, hypercytokinemia disappeared in a few days after birth; therefore, cord blood data analysis of cytokines and/or inflammation-related proteins concentrations is necessary to evaluate the fetal inflammatory environments in premature infants after birth.

Decreased serum osmolality promotes ductus arteriosus constriction.

AIMS: At birth, dynamic changes occur in serum components and haemodynamics, such as closure of the ductus arteriosus (DA). A previous study demonstrated that, in full-term human neonates, serum osmolality decreased transiently after birth, but recovered over the next few days. However, the significance of this transient decrease in osmolality has never been addressed. The objective of the present study was to examine the role of changes in serum osmolality after birth in DA closure. METHODS AND RESULTS: We found that rats exhibited a similar transient hypoosmolality after birth. Hypotonic stimulation induced constriction of DA rings and increased Ca(2+) transient in DA smooth muscle cells, but not in the aorta. The hypoosmotic sensor transient receptor potential melastatin 3 (TRPM3) was highly expressed in the rat DA, and TRPM3 silencing abolished the Ca(2+) response to hypoosmolality. Pregnenolone sulfate stimulation of TRPM3 induced rat DA constriction ex vivo and in vivo. Furthermore, hypertonic fluid injection impaired rat DA closure. In humans, neonatal serum hypoosmolality was observed in relatively mature preterm infants (≥28 weeks). In extremely preterm infants (<28 weeks), however, this hypoosmolality was absent. Instead, a rapid increase in osmolality occurred thereafter. Such an increase was greater, in particular, among patent DA (PDA) patients. CONCLUSIONS: A transient decrease in serum osmolality may promote DA closure during the first few days of life. Adjusting serum osmolality to proper levels might help to prevent the onset of PDA, improving the therapeutic outcome in extremely preterm infants.