Mortality, morbidity, growth and development of babies weighing 501-1,000 grams and 1,001-1,500 grams at birth.

During the five-year period, January 1980 to December 1984, 149 babies of extremely low birthweight (ELBW; 501-1,000 g) and 296 of very low birthweight (VLBW; 1,001-1,500 g) were admitted to King's College Hospital, Neonatal Intensive Care Unit. The survival rates were 51.7% and 82.8% respectively. There were more peri- and postnatal problems in the ELBW babies than the VLBW babies and these differences were highly significant. All surviving babies born between January 1980 and December 1982 were followed up until aged two. The ELBW children had a higher incidence of neuro-developmental sequelae than those of VLBW especially when both major and minor problems were considered. Their developmental quotients were lower at one and two years. Significantly more ELBW children were of short stature and low weight (less than 3rd centile). By two years of age the differences between ELBW and VLBW children in stature and mean DQ had lessened.