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ObjectiveTo investigate the effect of chorionicity， gestational age at birth and birth weight discordance on neonatal outcomes in twin pregnancies. MethodsWe conducted a population-based retrospective study of monochorionic diamniotic （MCDA） twin pregnancies and dichorionic diamniotic （DCDA） twin pregnancies who were admitted in the First Affiliated Hospital， Sun Yat-sen University from January 2015 to December 2020. A total of 1504 live-born twins were included， with 386 cases in MCDA group and 1118 cases in DCDA groups， respectively. The comparison of neonatal outcomes between MCDA and DCDA twins was performed using t-test， Wilcoxon rank sum test， Chi-square test or Fisher’s exact test. Logistic regression was performed to evaluate the effects of chorionicity， gestational age at birth， birth weight discordance and sex on neonatal outcomes. There were 168 live-born twins affected by inter-twin birth weight discordance≥25%， with 96 cases in MCDA group and 72 cases in DCDA groups， respectively. Logistic regression was performed to evaluate the effects of chorionicity， gestational age at birth， birth weight light or heavy （small twin or large twin） of the twin and sex on neonatal outcomes. ResultsAmong the 1 504 newborns， gestational age at birth was lower in MCDA group compared with DCDA group （P = 0.000）， and the degree of birth weight discordance was higher in MCDA group than that of the DCDA group （P = 0.001）. Birth asphyxia， respiratory distress syndrome （RDS）， bronchopulmonary dysplasia （BPD）， and sepsis were more frequency in MCDA group compared with DCDA group （P = 0.000， P = 0.000， P = 0.000， P = 0.000）. Low gestational age at birth was an independent risk factor for birth asphyxia， RDS， BPD， sepsis， necrotizing enterocolitis （NEC）≥stageⅡ， acute kidney injury （AKI）， retinopathy of prematurity （ROP）， and neonatal death respectively （P = 0.000， P = 0.000， P = 0.000， P = 0.000， P = 0.011， P = 0.000， P = 0.000， P = 0.000）. High degree of birth weight discordance was an independent risk factor for birth asphyxia， RDS， BPD， sepsis and ROP respectively （P = 0.045， P = 0.000， P = 0.000， P = 0.004， P = 0.017 ）. Chorionicity was not an independent risk factor for neonatal morbidity and death （P > 0.05）. Among the 168 twins with birth weight discordance ≥25%， low gestational age at birth was an independent risk factor for birth asphyxia， RDS， BPD， sepsis and ROP， respectively （P = 0.000， P = 0.000， P = 0.000， P = 0.000， P = 0.000）； small twin was an independent risk factor for birth asphyxia and BPD， respectively （ P = 0.013， P = 0.001）； chorionicity was not an independent risk factor for neonatal morbidity （P > 0.05）. ConclusionChorionicity was not an independent risk factor for adverse neonatal outcome in twin births. Low gestational age at birth and high degree of birth weight discordance were independent risk factor for adverse neonatal outcome in twin births. Small twins had increased risk of adverse neonatal outcome in twins with birth weight discordance ≥25%.
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In order to study the influence of distance weight on ore-grade estimation, the inverse distance weighted (IDW) is used to estimate the Ni grade and MgO grade of serpentinite ore based on a three-dimensional ore body model and related block models. Manhattan distance, Euclidean distance, Chebyshev distance, and multiple forms of the Minkowski distance are used to calculate distance weight of IDW. Results show that using the Minkowski distance for the distance weight calculation is feasible. The law of the estimated results along with the distance weight is given. The study expands the distance weight calculation method in the IDW method, and a new method for improving estimation accuracy is given. Researchers can choose different weight calculation methods according to their needs. In this study, the estimated effect is best when the power of the Minkowski distance is 3 for a 10 m × 10 m × 10 m block model. For a 20 m × 20 m × 20 m block model, the estimated effect is best when the power of the Minkowski distance is 9.
