Hara, Kaori

写真a

Affiliation

School of Medicine, Department of Pediatrics ( Shinanomachi )

Position

Researcher (Non-tenured) / Project Researcher(Non-tenured)

External Links
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Career 【 Display / hide 】

  • 2015.04
    -
    Present

    慶應義塾大学医学部小児科学教室, 助教

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Academic Background 【 Display / hide 】

  • 2002.04
    -
    2008.03

    Keio Univercity, medicine

    University, Graduated

  • 2018.04
    -
    2022.03

    Keio University, 医学部, 医学研究科博士課程

    Graduate School, Completed, Doctoral course

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Academic Degrees 【 Display / hide 】

  • 博士（医学）, Keio University, Coursework, 2022.03

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Licenses and Qualifications 【 Display / hide 】

  • 小児科専門医, 2013.10

  • 周産期（新生児）専門医, 2016.12

  • Board-Certified Clinical Geneticist, 2024.11

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Research Areas 【 Display / hide 】

  • Life Science / Genetics (ゲノムインプリンティング)

  • Life Science / Embryonic medicine and pediatrics

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Research Keywords 【 Display / hide 】

  • インプリンティング異常症

  • ビタミンD

  • 新生児学

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Papers 【 Display / hide 】

  • Impact of COVID-19-Related Social Restrictions on Vitamin D Levels in Japanese Newborns and Infants: A Retrospective Cohort Study.

    Seki Y, Hara-Isono K, Morisawa K, Hida M, Ikeda K

    The Keio journal of medicine  2026.07

    ISSN  0022-9717

  • Bidirectional changes in serum 25-hydroxyvitamin D in newborns during the first four days of life: A longitudinal cohort study.

    Ikeda K, Hara-Isono K, Morisawa K, Abe K

    Clinical nutrition ESPEN 73   103289 2026.04

    　View Summary

    Background & aims Little is known about short-term vitamin D dynamics during the immediate neonatal period. Most neonatal studies have relied on single-point measurements of 25-hydroxyvitamin D (25(OH)D), limiting understanding of early postnatal changes. In Japan, healthy full-term infants typically remain hospitalized for 4–5 days, receiving minimal vitamin D intake from small amounts of formula and experiencing virtually no sunlight exposure. This clinical setting provides a unique opportunity to investigate early postnatal vitamin D dynamics under conditions of minimal exogenous input. This study aimed to examine short-term changes in serum 25(OH)D from birth to day 4 of life (Δ25(OH)D) and determine how baseline vitamin D status influences these changes. Methods We analyzed 40 infants with paired cord blood and day 4 serum 25(OH)D measurements obtained by chemiluminescence immunoassay. Linear regression evaluated the association between cord blood 25(OH)D concentrations and Δ25(OH)D. Results Estimated vitamin D intake during hospitalization was 64 ± 18 IU/day, substantially below the 400 IU/day recommended by the American Academy of Pediatrics. Baseline-dependent bidirectional changes in serum 25(OH)D were observed: infants with lower cord blood concentrations increased, whereas those with higher baseline concentrations declined. Cord blood 25(OH)D concentrations were strongly inversely correlated with Δ25(OH)D (r = −0.745, p < 0.001). Regression analysis indicated an equilibrium point of approximately 21.4 ng/mL, at which no net change in serum 25(OH)D was expected. Conclusion This study provides the first quantitative description of short-term changes in neonatal 25(OH)D after birth and suggest dynamic physiological regulation of vitamin D during early life.

  • Weekly vitamin D supplementation during early infancy as a potential strategy to prevent vitamin D insufficiency: A two-center retrospective study

    Hara-Isono K., Morisawa K., Hida M., Iwamoto S., Ikeda K.

    Pediatrics and Neonatology 67 ( 2 ) 203 - 209 2026.03

    ISSN  18759572

    　View Summary

    Background: For preventing Vitamin D (VD) insufficiency, several VD supplementation guidelines were established worldwide. In Japan, no nationwide guidelines for preventing VD insufficiency have been implemented, whereas guidelines for preventing vitamin K (VK) deficiency-related bleeding recommend weekly supplementation of VK. The aim of this study is to clarify whether weekly VD plus VK supplementation during the early neonatal period prevents VD insufficiency at one month of age.MethodsWe retrospectively analyzed serum 25-hydroxyvitamin D (25(OH)D) levels of 555 one-month-old infants born between 2017 and 2023. Infants were classified into the control group (not supplemented), weekly group (1000 IU/week), and daily group (240 IU/day). We compared serum 25(OH)D levels among the three groups. Multivariable logistic regression analyses adjusted for formula intake and BMI were performed to better estimate the effect of VD supplementation on the prevention of VD insufficiency.ResultsWe included 414, 55, and 86 infants in the control, weekly, and daily groups, respectively. All infants received weekly supplementation of VK. Serum 25(OH)D levels in the weekly and daily groups were higher than those in the control group (median (ng/mL): control 9.7 vs weekly 22.2, P < 0.001; control vs daily 23.0, P < 0.001). The frequencies of VD insufficiency were 370/414 (89.4 %), 11/55 (20.0 %), and 22/86 (25.6 %) in the control, weekly, and daily groups, respectively. Adjusted odds ratios of VD insufficiency compared to the control were 0.038 (95 % confidence intervals (95 %CI): 0.017, 0.085) and 0.036 (95 %CI: 0.019, 0.067) in the weekly and daily groups, respectively. No infant with VD excess was observed.ConclusionOur results demonstrated that combined weekly supplementation of VD and VK during early infancy can prevent VD insufficiency at one month of age without causing VD excess. This finding may provide evidence for the development of nationwide prophylaxis for VD insufficiency in regions lacking specific guidelines.

  • Effects of maternal commercial supplementation on 25-hydroxyvitamin D levels in newborns: a retrospective cohort study in a single center, Saitama, Japan, 2022–2023

    Morisawa K., Ikeda K., Hida M., Hara-Isono K.

    Endocrine Journal 73 ( 2 ) 243 - 249 2026

    ISSN  09188959

    　View Summary

    Vitamin D (VD) insufficiency in pregnant women is a serious health problem worldwide. To prevent VD insufficiency during pregnancy, several guidelines recommend 600 IU/day VD for all pregnant women. In Japan, no national guidelines for preventing VD insufficiency have been implemented, and no study has evaluated adequate VD intake in pregnant women; however, the number of pregnant women taking commercial dietary supplements containing VD has increased in recent years. This study aimed to examine the effects of maternal commercial supplementation of VD on 25-hydroxyvitamin D (25(OH)D) levels in newborns. We retrospectively analyzed the serum 25(OH)D levels in 279 four-days-old newborns born at the Saitama City Hospital from 2022 to 2023. Newborns were classified into a supplement group (mothers who took VD-containing commercial supplements regularly throughout pregnancy; n = 103) and a non-supplement group (mothers who did not take any supplements during pregnancy; n = 176). The study findings revealed that serum 25(OH)D levels in newborns in the supplement group were higher than those in the non-supplement group (median [interquartile range]: supplement group 17.2 [14.6, 22.9] vs. non-supplement group 14.3 [11.6, 16.7], p < 0.001). In the supplement group, approximately 70% of newborns still showed VD insufficiency. Although the maternal use of VD-containing commercial supplements during pregnancy increased the serum 25(OH)D levels in newborns at four days of age, additional measures, such as VD supplementation for newborns, are needed to improve neonatal VD status.

  • Age-dependent discordance in chemiluminescent immunoassay-electrochemiluminescence immunoassay correlation for 25-hydroxyvitamin D measurement reveals methodological considerations for assessment in early infancy

    Ota M., Ikeda K., Morisawa K., Nakagawa T., Hida M., Hara-Isono K.

    Endocrine Journal 73 ( 4 ) 563 - 570 2026

    ISSN  09188959

    　View Summary

    Vitamin D (VD) status is assessed by measuring serum 25-hydroxyvitamin D (25(OH)D) levels using immunoassays. In December 2024, a Japanese diagnostic laboratory transitioned from chemiluminescent immunoassay (CLIA: LIAISON<sup>®</sup> 25 OH Vitamin D Total Assay) to an electrochemiluminescent immunoassay (ECLIA: Elecsys<sup>®</sup> Vitamin D Total III assay). Although these methods yield comparable results in adults, it remains unclear whether this applies to children, particularly newborns and infants. This study aims to clarify the impact of transition from CLIA to ECLIA on 25(OH)D levels during early infancy. Serum 25(OH)D levels were measured in 84 infants under three months old (67 under four days old) using both CLIA and ECLIA. Correlation and agreement were assessed using Passing–Bablok regression and Bland–Altman analyses, respectively. The obtained regression equation was applied to 252 age- and sex-matched cases from 2,253 historical controls in the registry to evaluate changes in VD classification. The regression equation was Y<inf>ECLIA</inf> = 0.846X<inf>CLIA</inf> – 2.281 (τ = 0.53, p < 0.001). Bland–Altman analysis revealed a constant negative bias of –4.89 ± 3.53 ng/mL [–5.66, –4.12] (mean ± standard deviation [95% confidence interval]) for ECLIA versus CLIA. Reclassification revealed an increase in VD deficiency (25(OH)D < 12 ng/mL) from 27.8% to 61.9%, and VD insufficiency (25(OH)D < 20 ng/mL) from 75.4% to 91.7%. The transition from CLIA to ECLIA led to lower measured 25(OH)D levels in newborns and infants and increased VD deficiency and insufficiency diagnoses. Method-specific differences should be considered when evaluating VD status during early infancy, particularly in infants under four days.

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

  • 周産期におけるビタミンD誘導体 (3-epi-25(OH)D3) の役割の解明

    2025.04
    -
    2028.03

    Principal investigator

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Awards 【 Display / hide 】

  • 2022年度臨床研究Award

    2022.06, 日本周産期・新生児医学会, 早期新生児期から開始するビタミンD週1回投与により、乳児のVitamin D insufficiency を予防できるか

    Type of Award： Award from Japanese society, conference, symposium, etc.

  • 第3回SMF論文表彰制度奨励賞

    2021.11, 杉山記念財団, 30歳以上の女性における生殖補助医療はエピ変異によるインプリンティング疾患発症のリスク因子と成り得る

    Type of Award： Award from publisher, newspaper, foundation, etc.

  • 第43回日本小児遺伝学会大会長賞

    2021.01, 日本小児遺伝学会, 30歳以上の女性における生殖補助医療はエピ変異によるインプリンティング疾患発症のリスク因子と成り得る

    Type of Award： Award from Japanese society, conference, symposium, etc.

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