Population-based Study of Chronic Lung Disease in Very Low Birth Weight Infants in North Carolina in 1994 With Comparisons With 1984

Objective. To assess the pulmonary outcomes of very low birth weight (VLBW) infants in North Carolina in 1994 and to compare rates of survival and chronic lung disease (CLD) between 1994 and 1984 (see reference 2). Methods. Data were collected prospectively by collaborators from all 13 neonatal intensive care units in North Carolina to determine survival and pulmonary outcomes of infants with birth weights of 500 to 1500 g. State vital statistics data were used to confirm completeness of the sample. CLD was defined as oxygen or ventilator therapy at 36 weeks’ postmenstrual age (PMA). For comparisons with the 1984 cohort, survival and pulmonary outcomes of infants defined to be at risk for CLD (ventilated >48 hours and survived 30 days) were recorded at 30 days, 3 months, and 6 months of postnatal age. Results. Outcome data were available for 1413 (92%) of the in-state VLBW live births. Of VLBW infants, 224 (15%) died before 48 hours of age. The overall rate of CLD in 1994 at 36 weeks’ PMA was 25%. Rates by birth weight group were 57% for 500 to 750 g birth weight (BW), 41% for 751 to 1000 g BW, 19% for 1001 to 1250 g BW, and 8% for 1251 to 1500 g BW. Infants who received ventilator therapy for >48 hours accounted for 89% of the CLD cases. The CLD rate at 36 weeks’ PMA in infants weighing 751 to 1500 g was 37% for those ventilated >48 hours versus 5% for those ventilated <48 hours (OR: 7.1; 95% CI: 4.4–11.3). Overall survival in 1994 was significantly higher for infants than in 1984 (78% vs 74%), most notably in infants 500 to 750 g BW (37% vs 24%), and 751 to 1000 g BW (82% vs 65%). When compared with 1984, the CLD rates in those infants defined to be at risk were significantly higher in 1994 at 30 days (68% vs 54%) and at 3 months (24% vs 15%) of postnatal age. For at-risk infants in 1994, there were fewer infants on the ventilator, but more infants on oxygen alone at all measured time points compared with 1984. Conclusion. Survival of VLBW infants has improved since 1984. Ventilator therapy for >48 hours remains a significant risk factor for CLD. The incidence of CLD has increased from 1984 to 1994 but has shifted from ventilator to oxygen therapy. Pediatrics 1999;104(2). URL: http://www.pediatrics.org/cgi/content/full/104/2/e17; bronchopulmonary dysplasia, epidemiology, infant, low birth weight, intensive care units, neonatal statistics, infant mortality, prospective studies. ABBREVIATIONS. VLBW, very low birth weight; CLD, chronic lung disease; NICU, neonatal intensive care unit; PMA, postmenstrual age. The incidence of very low birth weight (VLBW) births remains an important public health concern in the United States. In 1994, 1.3% of all infants born in the United States weighed ,1500 g at birth.1 Collectively, disorders relating to short gestation represent the second leading cause of infant mortality, accounting for 13% of all infant deaths in the United States in 1994 and 1995.1 VLBW infants often require complex, lengthy, and costly medical management. In addition, these infants experience multiple morbidities, the most common being infantile chronic lung disease (CLD). Kraybill et al2 reported the incidence of CLD in 1984 from a population-based study of VLBW infants in North Carolina. This study defined an at-risk population as those who received assisted ventilation for .48 hours and who had survived 30 days. The CLD rate for these at-risk VLBW infants at 30 days of age was 54%. Recent studies in the postsurfactant era have reported 30-day CLD rates of 27%,3 31%,4 and 6%.5 These multicenter studies reported outcomes for all VLBW infants admitted to participating neonatal intensive care units (NICUs) rather than for a defined at-risk population. The data of Palta et al3 suggested an increase in CLD from the presurfactant to postsurfactant period, but survival without CLD morbidity did not change. We performed a population-based study of VLBW infants in North Carolina to determine survival and rates of CLD. To identify the impact of perinatal and neonatal therapies introduced in the past decade, changes in outcomes were investigated by comparing these results with the study conducted by Kraybill et al.2