Prediction of survival for preterm births by weight and gestational age: restrospective population based study

Objective To produce current data on survival of preterm infants. Design Retrospective population based study. Setting Trent health region. Subjects All European and Asian live births, stillbirths, and late fetal lo sses from 22 to 32 weeks' gestation, excluding those with major congenital malformations, in women resident in the Trent health region between 1 Janua ry 1994 and 31 December 1997. Main outcome measures Birth weight and gestational age specific survival fo r both European and Asian infants (a) known to be alive at the onset of lab our and (b) admitted for neonatal care. Results 738 deaths occurred in 3760 infants born between 22 and 32 weeks' g estation during the study period, giving an overall survival rate of 80.4%. The survival rate for the 3489 (92.8%) infants admitted for neonatal care was 86.6%. For European infants known to be alive at the onset of labour, s ignificant variations in gestation specific survival by birth weight emerge d from 24 weeks' gestation: survival ranged from 9% (95% confidence interva l 7% to 13%) for infants of birth weight 250-499 g to 21% (16% to 28%) for those of 1000-1249 g. At 27 weeks' gestation, survival ranged from 55% (49% to 61%) for infants of birth weight 500-749 g (below the 10th centile) to 80% (76%, to 85%) for those of 1250-1499 g. Infants who were large for date s (greater than or equal to 27 weeks' gestation) had a slightly reduced, bu t not significant, predicted survival. Similar survival rates were observed for Asian infants. The odds ratio for the survival of infants from a multi ple birth compared with singleton infants was 1.4 (1.1 to 1.8). Survival gr aphs for infants admitted for neonatal care are presented by sex. Conclusion Easy to use birth weight and gestational age specific predicted survival graphs for preterm infants facilitate decision making for clinicia ns and parents. It is important that these graphs are representative, are p roduced for a geographically defined population, and are not biased towards the outcomes of particular centres. Such graphs, produced in two stages, a llow for the changing pattern of survival of infants from the start of the intrapartum period to immediately after admission for neonatal care.