Objective:To investigate the association between serum 25-hydroxy vitamin D [25-(OH)D] levels at 1 and 4 weeks after birth and bronchopulmonary dysplasia (BPD) in preterm infants.Methods:This case-control study included 125 preterm infants (gestational age<32 weeks) admitted to the Department of Neonatology, Hangzhou Women's Hospital between January 2020 and December 2022. All infants received vitamin D supplementation (900 IU/d) starting at 1 week after birth. According to the clinical diagnosis at 28 d after birth, these participants were divided into BPD ( n=57) and non-BPD ( n=68) groups. Two independent sample t-test, Wilcoxon rank-sum test, and Chi-square test were used to compare the general conditions, maternal perinatal conditions, postnatal treatment, complications, and 25-(OH)D levels between the two groups. Pearson bivariate correlation and partial correlation analyses were performed to assess the relationship between 25-(OH)D levels and BPD. Results:The BPD group had lower gestational age [(28.7±1.8) vs. (30.2±0.9) weeks, t=－6.13], birth weight [(1 166.1±238.1) vs. (1 473.8±224.4) g, t=－7.42], and Apgar scores at 1 min [(7.6±2.1) vs. (9.1±1.3) scores, t=－4.58) and 5 min [(8.9±1.2) vs. (9.5±1.1) scores, t=－2.77) compared to the non-BPD group (all P<0.05). The proportion of infants received surfactant therapy [73.7% (42/57) vs. 50.0% (34/68), χ2=7.30], the incidence of maternal preeclampsia [29.8% (17/57) vs. 14.7% (10/68), χ2=4.19], and the incidence of neonatal asphyxia [31.6% (18/57) vs. 16.2% (11/68), χ2=4.13], pneumonia [14.0% (8/57) vs. 1.5% (1/68), χ2=5.57], sepsis [64.9% (37/57) vs. 19.1% (13/68), χ2=27.10], and patent ductus arteriosus [78.9% (45/57) vs. 48.5% (33/68), χ2=12.23] were higher in the BPD group than in the non-BPD group (all P<0.05). The infants with BPD required longer durations of caffeine therapy [(37.2±15.1) vs. (16.8±11.5) d, t=8.58], mechanical ventilation [0.0 (0.0-3.0) vs. 0.0 (0.0-0.0) d, Z=3.52], non-invasive ventilation [23.0 (11.0-31.0) vs. 6.0 (4.0-9.0) d, Z=6.22], total oxygen therapy [46.0 (40.0-58.0) vs. 13.0 (6.0-19.0) d, Z=6.57], and hospitalization [(60.7±15.0) vs. (37.6±7.8) d, t=10.52] than those without BPD (all P<0.05). Serum 25-(OH)D levels were significantly lower in the BPD group than in the non-BPD group at both 1 week [(32.75±7.81) vs. (43.07±9.36) nmol/L, t=－4.60, P<0.001] and 4 weeks [(49.03±11.12) vs. (60.02±14.39) nmol/L, t=－3.90, P<0.001] after birth. Vitamin D deficiency at 1 week after birth was more prevalent in the BPD group than in the non-BPD group [40.0% (10/25) vs. 12.5% (5/40), χ2=6.55, P=0.010]. Serum 25-(OH)D levels at 1 and 4 weeks after birth were negatively correlated with BPD incidence (bivariate analysis: r=－0.50 and－0.40; partial correlation analysis corrected with birth gestational age, birth weight and other general information, the proportion of preeclampsia/cesarean section and other perinatal information of pregnant women, sepsis/mechanical ventilation time and other postnatal diseases and treatment conditions: r=－0.37 and－0.27; both P<0.05). Conclusion:Low serum 25-(OH)D levels at 1 and 4 weeks after birth may be associated with BPD in preterm infants.

Objective:To investigate the association between serum 25-hydroxy vitamin D [25-(OH)D] levels at 1 and 4 weeks after birth and bronchopulmonary dysplasia (BPD) in preterm infants.Methods:This case-control study included 125 preterm infants (gestational age<32 weeks) admitted to the Department of Neonatology, Hangzhou Women's Hospital between January 2020 and December 2022. All infants received vitamin D supplementation (900 IU/d) starting at 1 week after birth. According to the clinical diagnosis at 28 d after birth, these participants were divided into BPD ( n=57) and non-BPD ( n=68) groups. Two independent sample t-test, Wilcoxon rank-sum test, and Chi-square test were used to compare the general conditions, maternal perinatal conditions, postnatal treatment, complications, and 25-(OH)D levels between the two groups. Pearson bivariate correlation and partial correlation analyses were performed to assess the relationship between 25-(OH)D levels and BPD. Results:The BPD group had lower gestational age [(28.7±1.8) vs. (30.2±0.9) weeks, t=－6.13], birth weight [(1 166.1±238.1) vs. (1 473.8±224.4) g, t=－7.42], and Apgar scores at 1 min [(7.6±2.1) vs. (9.1±1.3) scores, t=－4.58) and 5 min [(8.9±1.2) vs. (9.5±1.1) scores, t=－2.77) compared to the non-BPD group (all P<0.05). The proportion of infants received surfactant therapy [73.7% (42/57) vs. 50.0% (34/68), χ2=7.30], the incidence of maternal preeclampsia [29.8% (17/57) vs. 14.7% (10/68), χ2=4.19], and the incidence of neonatal asphyxia [31.6% (18/57) vs. 16.2% (11/68), χ2=4.13], pneumonia [14.0% (8/57) vs. 1.5% (1/68), χ2=5.57], sepsis [64.9% (37/57) vs. 19.1% (13/68), χ2=27.10], and patent ductus arteriosus [78.9% (45/57) vs. 48.5% (33/68), χ2=12.23] were higher in the BPD group than in the non-BPD group (all P<0.05). The infants with BPD required longer durations of caffeine therapy [(37.2±15.1) vs. (16.8±11.5) d, t=8.58], mechanical ventilation [0.0 (0.0-3.0) vs. 0.0 (0.0-0.0) d, Z=3.52], non-invasive ventilation [23.0 (11.0-31.0) vs. 6.0 (4.0-9.0) d, Z=6.22], total oxygen therapy [46.0 (40.0-58.0) vs. 13.0 (6.0-19.0) d, Z=6.57], and hospitalization [(60.7±15.0) vs. (37.6±7.8) d, t=10.52] than those without BPD (all P<0.05). Serum 25-(OH)D levels were significantly lower in the BPD group than in the non-BPD group at both 1 week [(32.75±7.81) vs. (43.07±9.36) nmol/L, t=－4.60, P<0.001] and 4 weeks [(49.03±11.12) vs. (60.02±14.39) nmol/L, t=－3.90, P<0.001] after birth. Vitamin D deficiency at 1 week after birth was more prevalent in the BPD group than in the non-BPD group [40.0% (10/25) vs. 12.5% (5/40), χ2=6.55, P=0.010]. Serum 25-(OH)D levels at 1 and 4 weeks after birth were negatively correlated with BPD incidence (bivariate analysis: r=－0.50 and－0.40; partial correlation analysis corrected with birth gestational age, birth weight and other general information, the proportion of preeclampsia/cesarean section and other perinatal information of pregnant women, sepsis/mechanical ventilation time and other postnatal diseases and treatment conditions: r=－0.37 and－0.27; both P<0.05). Conclusion:Low serum 25-(OH)D levels at 1 and 4 weeks after birth may be associated with BPD in preterm infants.