対象・方法：2010 ～ 2016 年に当院でインドメタシン予防投与を行った超低出生体重児71 例。予防投与後も動脈管 開存症に対し治療投与や動脈管結紮術を必要とした症例を治療群，それ以外を非治療群に分け，患者背景，合併症 について診療録から後方視的に検討した。
結果：治療群は28 例，非治療群は43 例だった。在胎週数や出生体重，合併症の頻度は両群間に差を認めなかった。 母体の硫酸マグネシウム投与は治療群に多く（78.6％ vs. 51.2％；P＝0.020），臍帯血Mg 値は治療群が有意に高値 だった（3.75mg/dL vs. 2.25mg/dL；P＝0.002）。それ以外に有意差を認めた項目はなかった。
結論：母体に硫酸マグネシウムを投与され，出生時に高Mg 血症を認める超低出生体重児は，インドメタシン予防 投与後も動脈管が閉鎖せずに追加治療を必要とする可能性がある。
Methods：Analyses were carried out in 71 infants receiving prophylactic indomethacin, among 133 ELBW infants admitted to Nagaoka Red Cross Hospital between January 2010 and December 2016. Patients in whom the ductus arteriosus was closed owing to prophylactic indomethacin were included in the non-treatment group, and patients in whom indomethacin administration and surgery were performed for patent ductus arteriosus （PDA） after prophylactic indomethacin were included in the treatment group. We retrospectively examined the background and complications of patients using medical records and compared the two groups.
Results：There were 43 patients in the non-treatment group and 28 patients in the treatment group. Incidence of maternal magnesium sulfate （MgSO4） administration was significantly higher in the treatment group than in the nontreatment group（ 78.6％ vs. 51.2％；P＝0.020）. The serum magnesium level of cord blood was significantly higher in the treatment group than in the non-treatment group （3.75mg/dL vs. 2.25mg/dL；P＝0.002）. There were no significant differences between the two groups in terms of other background factors or complications.
Conclusions：ELBW infants exposed to MgSO4 by maternal administration and who have hypermagnesemia at birth may require additional treatment for PDA after prophylactic indomethacin.
