Trends in Mortality and Morbidity for Very Low Birth Weight Infants, 1991–1999

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Abstract
Background. Medical care for very low birth weight (VLBW) infants and their mothers has changed dramatically during the 1990s, yet it is unclear how these changes have affected mortality and morbidity. Objective. We used the Vermont Oxford Network Database to identify trends in clinical practice and patient outcomes for VLBW infants born from 1991 to 1999. Methods. Logistic regression was used to evaluate temporal trends in practices and outcomes while adjusting for patient characteristics and accounting for clustering of cases within hospitals. Results. There were 118 448 infants 501 to 1500 g from 362 neonatal intensive care units enrolled in the Network Database from 1991 to 1999. Prenatal care, cesarean section, multiple births, antenatal steroids, and 1-minute Apgar scores increased during this period, as did the use of nasal continuous positive airway pressure, high-frequency ventilation, surfactant, and postnatal steroids. The proportion of white infants decreased; the proportions of Hispanic infants and those of other races increased. The crude and adjusted rates of mortality, pneumothorax, intraventricular hemorrhage (IVH), and severe IVH declined from 1991 to 1995, whereas from 1995 to 1999, the rates of mortality, IVH, and severe IVH did not change significantly, and pneumothorax increased. Conclusions. There have been major changes in both obstetric and neonatal care during the 1990s. These changes were associated with decreases in mortality and morbidity for VLBW infants during the first half of the decade. However, since 1995, no additional improvements in mortality or morbidity have been seen, ending a decades-long trend of improving outcomes for these infants.