Neurodevelopmental outcomes of extremely low birth weight infants <32 weeks' gestation between 1993 and 1998. 
This study evaluated the impact of changes in perinatal management on neurodevelopmental impairment (NDI) at 18 to 22 months' corrected age of low gestation (22-26 weeks) and higher gestation (27-32 weeks) extremely low birth weight infants (401-1000 g birth weight) who were cared for in the National Institute of Child Health and Human Development Neonatal Research Network during 3 epochs (1993-1994, 1995-1996, and 1997-1998).  It was hypothesized that outcomes would improve over the 3 epochs.  A multicenter cohort study was conducted of the outcomes of 3785 infants with assessments at 18 to 22 months' corrected age.  Regression analyses were completed to evaluate for epoch effects, gestational age effects, and time plus gestational age interaction.  Regression analyses were also performed to identify the independent associations of epoch and 4 study perinatal interventions: antenatal steroids (yes, no), high-frequency ventilation (yes, no), number of days to regain birth weight as a marker of nutritional intake, and postnatal steroids for treatment of bronchopulmonary dysplasia (yes, no) with outcomes.  Survival improved for both the low (55%-61%) and higher (82%-86%) gestational age groups during the 3 epochs.  Regression analyses indicated that the decreased risk for adverse outcome was significantly lower in epoch 2 compared with epoch 1 with decreased rates of low Bayley Mental Development Index (MDI) and neurodevelopmental impairment (NDI).  Antenatal steroids were associated with decreased risk for moderate to severe cerebral palsy (CP) and low Bayley Psychomotor Development Index.  High-frequency ventilation was associated with a low Bayley MDI and NDI, and postnatal steroids were associated with moderate to severe CP, any CP, low Bayley MDI, low Bayley Psychomotor Development Index, and increased NDI.  Survival of extremely low birth weight infants improved between 1993 and 1998.  Although some outcomes remained unchanged, the rates of low Bayley MDI scores and NDI improved.  Antenatal steroid administration was the only study intervention associated with improved outcomes.