Improved Outcomes for Very-Low-Birthweight Infants: Evidence From a New Zealand National Population-Based Data

Abstract

The survival chances of very-low-birthweight (VLBW) infants, weighing less than 1500 g, continue to improve, and obstetricians today are more willing to intervene in earlier gestations. Nevertheless, debate continues about the propriety of offering neonatal intensive care for very preterm infants, especially those whose viability is in question. This prospective study compared survival and short-term morbidity in VLBW infants born in New Zealand in 1986 and 1998 through 1999. Data were collected from birth until discharge from the hospital or death. In 1986, 413 VLBW infants, representing 0.78% of live births, were admitted for intensive care. In 1998 through 1999 the number increased to 1084 or 0.96% of all live births, a 31% rise. The proportion of infants weighing 1000 to 1499 g at birth increased 20% from the earlier to the later period, whereas infants weighing 500 to 999 g increased 51%. Survival was significantly higher in 1998 through 1999 for all birth-weight groups, and 38% of 13 infants weighing less than 500 g survived in this period. There was a small reduction in overall median birthweight and gestation in the later period. Fewer infants born in 1998 through 1999 had a 5-minute Apgar score less than 7, and more were exposed to antenatal corticosteroids. There was no substantial difference in the risk of hyaline membrane disease, but more infants in the later period who lived 28 days received assisted ventilation (87% vs. 74% in the earlier group). Chronic lung disease was less frequent in the later period than in 1986, especially in infants weighing 1000 to 1499 g at birth. The same was the case for severe retinopathy of prematurity. The incidence of periventricular leukomalacia was probably higher in 1986. Survival of VLBW infants has improved, significantly in recent years even though more extremely low-birthweight infants are being admitted. At the same time, surviving infants have not experienced more short-term morbidity. Improved regionalization of neonatal intensive care is probably part of the reason, along with the wider use of antenatal steroids, treatments such as exogenous surfactant, and improved technology in the neonatal intensive-care unit.