Objective: To ascertain the growth characteristics, delivery room management and hospital mortality of very preterm liveborn infants (< 33 weeks of gestation) and to identify differences between infants associated with the aetiological factor related to their very preterm delivery.
Design: Cohort analytical study.
Setting: King Edward Memorial Hospital for Women, Western Australia.
Main variables examined: Gestational age, birthweight, birthweight ratio, condition at birth and mortality.
Results: Six hundred and ninety-three liveborn very preterm infants were born to 608 mothers between 1.1.90 and 31.12.91. This was 1.37% of all liveborns in Western Australia. Three hundred and eighty-five (55.6%) were male. Growth characteristics (birthweight, birthweight ratio and proportion small for gestational age) differed between infants depending on the primary obstetric complication associated with the very preterm delivery. Overall 217 (31%) infants were small for gestational age, 34(4.9%) had a congenital anomaly, and 102 (14.7%) died. Corrected mortality, excluding major fatal congenital anomaly, was 86 (12.7%). The majority of infants died on the first day (n = 59 (57.8%)). The only factors associated with an increased or decreased mortality were decreasing gestation (adjusted odds ratio (AOR) 1.7, 95% CI 1.50-1.93), decreasing birthweight ratio (small for gestational age) (AOR 1.3, 95% CI 1.08-1.53), antepartum haemorrhage as primary complication (AOR 3.1, 95% CI 1.25-7.69) and any antenatal steroids (AOR 0.26, 95% CI 0.14-0.51). In comparison with other studies, survival in the extremely preterm group, defined as a gestational age of less than 28 weeks, is improving.
Conclusions: Very preterm infants account for a large proportion of perinatal mortality. Further studies are required to explore the differences between infants on the basis of the primary obstetric complication and to ensure that increased survival is not associated with an increase in disabilities.