Abstract 1405 Poster Session III, Monday, 5/3 (poster 24)

INTRODUCTION: In a previous study of very low birth weight (VLBW) neonates admitted to the Vanderbilt Neonatal Intensive Care Unit (NICU) from 1976-90, improvements in neonatal survival were accompanied by a corresponding increase in the incidence of BPD. Since then, certain neonatal and perinatal interventions have become standard practice (eg. surfactant replacement therapy) and may influence neonatal outcomes. In this study we have continued the analysis of the incidence of three outcomes for an additional seven years, 1991-97: (1) neonatal death (NEOD), defined as death within 28 days after birth; (2) BPD, diagnosed at 28 days postnatal age; and (3) the combined adverse outcome of NEOD of BPD (NEOD/BPD).

METHODS: To study any changes in the incidence of NEOD, BPD, and NEOD/BPD over time we modeled the probability of each of these outcomes among 3838 VLBW infants (<1500g) admitted within 24 hours of birth to the Vanderbilt NICU as a function of time period (1=1976-80, 2=1981-85, 3=1986-90, 4=1991-95, and 5=1996-97). Multiple logistic regression models were used to adjust for relevant covariates: birth weight, gender, race, birth location, gestational age (GA), maternal age, maternal diabetes, delivery method, multiple birth, birth order, Apgar score at 1 and 5 minutes diagnosis of hyaline membrane disease, and biologically relevant interactions among these covariates. For each outcome, only important confounders and effect modifiers were retained in the final model. Adjusted odds ratios and 95% confidence intervals were calculated to measure the risk associated with a given time period in comparison with the preceding 5yr period.

RESULTS: The results of the analysis shown in the table below assume a GA of 26 weeks. Similar trends were observed in other gestational age groups. There is a progressive decline in neonatal death across all periods. The previously described increase in BPD through period 3 is followed by a decrease in period 4 and 5. Risk of NEOD/BPD remained fairly constant from period 1 to 3, but then also demonstrated a significant decrease over the two most recent periods.

Table 1 No caption available
Full size table

CONCLUSIONS: In this large NICU, the increasing incidence of BPD seen in the 1970's and 1980's has been replaced by declining incidence in the 1990's, even though survival continues to improve. If these results are representative of other NICU's, the impact of BPD as a public health concern is diminishing.

(Supported by NIH HL56697)