Improved outcomes for very low birthweight infants: Evidence from New Zealand national population based data

Abstract

Objective: To compare the survival and short term morbidity of all New Zealand very low birthweight (VLBW) infants born in two epochs, 1986 and 1998-1999. Setting: All level III and level II neonatal intensive care units (NICUs) in New Zealand. Methods: In 1986, data were prospectively collected for a study of retinopathy of prematurity (ROP). In 1998-1999, prospective data were collected by the Australian and New Zealand Neonatal Network (ANZNN). Both cohorts included all VLBW infants born during the calendar year and admitted to a NICU. Data were collected from birth until discharge home or death. Results: More VLBW infants were admitted for care in 1998-1999 (n = 1084, 0.96% of livebirths) than in 1986 (n = 413, 0.78% of livebirths; p < 0.001), including a higher proportion of VLBW infants of < 1000 g birth weight (38% v 32% respectively; p < 0.05). Survival to discharge home increased from 81.8% in 1986 to 90.3% in 1998-1999 (p < 0.001). The 1998-1999 cohort had a higher proportion of infants born in a hospital with a level III NICU (87% v72% in 1986; p < 0.001) and receiving antenatal corticosteroids (80% v 58% in 1986; p < 0.001). In 1998-1999, the incidence of several morbidities had decreased compared with 1986, including oxygen dependency at 28 days (29% v 39% respectively; p = 0.001) and at 36 weeks postmenstrual age (16% v 23%; p = 0.002), grade 1 intraventricular haemorrhage (IVH) (8% v 24%; p < 0.001), grade 2/3 IVH (5% v 11%; p < 0.001), and stage 3/4 ROP for infants < 1000 g (6% v 13%; p < 0.001). Conclusions: The outlook for VLBW infants in New Zealand has improved since 1986.