Objective:To analyze the risk factors and clinical features of premature infants with bronchopulmonary dysplasia(BPD)at high altitude in Tibet and low altitude in Beijing.Methods:A retrospective case-control study was conducted.The clinical data of children with gestational age ≤32 weeks admitted to the Department of Neonatology of Lhasa People′s Hospital(altitude of 3 600 m)and the Department of Neonatology of Children′s Hospital Affiliated to Capital Institute of Pediatrics(altitude of 50 m)from January 1, 2018 to December 31, 2021 were collected.Cases were divided into BPD group and non-BPD group.Premature infants with BPD were divided into high altitude group and low altitude group according to different altitudes.The clinical characteristics and high risk factors of BPD were analyzed.Results:There were 379 premature infants with gestational age ≤32 weeks, 351 were included in the study, including 110 cases in group and 241 cases in non-BPD group.There were 48 cases in high altitude group and 62 cases in low altitude group.The incidence of BPD in high altitude areas(Lhasa)was 38.7%(48/124), among which mild, moderate and severe BPD accounted for 75.0%(36 cases), 18.8%(9 cases)and 6.3%(3 cases), respectively.The incidence rates of BPD were 100%(2/2), 86.7%(13/15)and 38.7%(33/107) in gestational age <28 weeks, 28 to 29 + 6 weeks and 30 to 32 weeks, respectively.There was a statistically significant difference among different gestational age groups( χ2=19.696, P<0.001). The incidence of BPD in low altitude areas(Beijing)was 27.3%(62/227), among which mild, moderate and severe BPD accounted for 74.2%(46 cases), 4.8%(3 cases)and 21.0%(13 cases), respectively.The incidence rates of BPD in gestational age<28 weeks, 28 to 29 + 6 weeks and 30 to 32 weeks were 100%(15/15), 45.6%(36/79)and 8.3%(11/133), respectively.There was a statistically significant difference among different gestational age groups( χ2=77.474, P<0.001). The incidence of BPD in high altitude areas was significantly higher than that in low altitude areas( χ2=4.841, P=0.028). Multivariate regression analysis showed that high altitude( OR 146.893, 95% CI 19.044-1 133.064), birth weight( OR 0.996, 95% CI 0.993-0.999), asphyxia( OR 4.187, 95% CI 3.020-21.670), non-invasive mechanical ventilation( OR 1.171, 95% CI 1.106-1.240)and invasive mechanical ventilation( OR 1.198, 95% CI 1.065-1.347)were significantly correlated with the occurrence of BPD.The gestational age at birth, small for gestational age infant, the fraction of inspired oxygen and the incidence of pregnancy induced hypertension in pregnant women in high altitude group were higher than those in low altitude group( P<0.05). The incidence of patent ductus arteriosus, the use time of noninvasive and invasive mechanical ventilation, the length of hospital stay, the age of mother, the application of prenatal hormone and the twin ratio in high altitude group were significantly lower than those in low altitude group( P<0.05). Conclusion:High altitude in Tibet is a high-risk factor for the occurrence of BPD in preterm infants.Strengthening maternal health care in high altitude areas of Tibet and doing a good job in asphyxia resuscitation in delivery room may be important measures to reduce BPD in preterm infants.

Objective:To investigate the incidence and risk factors of hypertensive disorders in pregnancy (HDP) in high altitude areas and their influence on maternal and infant outcomes.Methods:This was a retrospective case-control study. A total of 220 newborns were selected as the high altitude group, who were born to 216 mothers with HDP and admitted to the Neonatal Intensive Care Unit of the Lhasa People's Hospital from June 1, 2018, to June 1, 2020. The low altitude group consisted of 235 newborns born to 231 mothers with HDP and admitted to the Department of Neonatology of the Children's Hospital Affiliated to Beijing Capital Institute of Pediatrics from January 1, 2018, to December 31, 2021. Differences in the types of HDP between the two groups and the risk factors for the high incidence of preeclampsia-eclampsia and early-onset preeclampsia in high altitude area were analyzed. The influences of HDP in high and low altitude areas on maternal and infant outcomes were compared. Statistical analysis was performed using t-test, Mann-Whitney U test, Pearson Chi-square test, or continuous correction Chi-square test, and univariate and multivariate logistic regression analysis. Results:Maternal age and the proportions of primiparae and women of advanced age or having irregular prenatal examination were greater in the high altitude group than those in the low altitude group (all P<0.05). Besides, the incidence of early-onset preeclampsia, eclampsia, preeclampsia-eclampsia, and chronic hypertension complicated by preeclampsia were also higher in the high altitude group (all P<0.05). Multivariate logistic regression analysis showed that high altitude was a risk factor for the development of preeclampsia-eclampsia ( OR=4.437, 95% CI:2.582-7.626). Adverse pregnancy history ( OR=2.576, 95% CI:1.217-5.452) and irregular prenatal examination ( OR=2.862, 95% CI:1.412-5.800) were independent risk factors for early-onset preeclampsia in pregnant women in high altitude areas. Twin-pregnancy was a protective factor for early-onset preeclampsia in pregnant women in high altitude areas ( OR=0.183, 95% CI: 0.054-0.623). The incidence of maternal heart failure [7.9% (17/216) vs 0.4% (1/231), χ2=15.98], placental abruption [7.9% (17/216) vs 3.5% (8/231), χ2=4.11], hemolysis, elevated liver function and low platelet count syndrome [14.4% (31/216) vs 1.7% (4/231), χ2=24.64], premature delivery [86.1% (118/216) vs 73.6% (170/231), χ2=10.79], fetal growth restriction [52.3% (115/220) vs 18.7% (44/235), χ2=56.26], fetal distress [18.2% (40/220) vs 8.1% (19/235), χ2=10.26], neonatal asphyxia [29.5% (65/220) vs 11.1% (26/235), χ2=24.26], severe asphyxia [8.6% (19/220) vs 2.6% (6/235), χ2=8.10] and the proportion of neonates requiring mechanical ventilation within 24 h after birth [69.5% (153/220) vs 42.6% (100/235), χ2=33.54] as well as neonatal death within 7 d after birth [5.5% (12/220) vs 1.3% (3/235), χ2=6.22] in the high altitude group were significantly higher than those in the low altitude group (all P<0.05). Conclusion:High altitude is a risk factor for preeclampsia-eclampsia, and the adverse effects of HDP on mothers and infants are more severe in high altitude areas.