Objective
Moderately preterm infants account for a large proportion of admissions and bed-days
in neonatal units. Determinants of length of hospital stay, contemporary measures of
morbidity by gestational week and risk factors predicting neonatal morbidity have been
poorly studied. The overall purpose of this thesis was to fill these gaps with knowledge
to make neonatal care more effective, and to improve short- and long-term outcome for
moderately preterm infants.
Methods
Observational studies on length of hospital stay for moderately preterm infants in a
longitudinal perspective over 20 years (Paper I) and a cross-sectional multicenter
survey (Paper II) were performed. Risk factors for prolonged length of stay were
determined in Paper II. Neonatal outcomes were studied in two national populationbased
studies. Paper III explored neonatal morbidity and interventions stratified by
gestational week. In Paper IV, rates of transient tachypnea of the newborn (TTN) and
respiratory distress syndrome (RDS) among moderately preterm infants were compared
to corresponding rates in late preterm to term infants, and risk factors for these acute
respiratory morbidities were evaluated.
Results
Paper I found that length of stay decreased by an average of 14 days from 1983 to
2002, in spite of no concomitant decrease in neonatal morbidity. Paper II showed that
only 13% of the variation in length of stay in Swedish neonatal units (which differed up
to two weeks) could be attributed to neonatal morbidity. In Paper III, overall rates of
common neonatal morbidities were found to vary between 15 and 59% in moderately
preterm infants, with a strong inverse relation to birth weight standard deviation score
and gestational age at birth. Paper IV demonstrated that besides low gestational age,
Cesarean section, male sex and low Apgar score are associated to significantly
increased risks for TTN and RDS in moderately preterm infants.
Conclusions
Whereas neonatal morbidity has remained essentially unchanged and high, length of
hospital stay has decreased significantly for moderately preterm infants during the last
20 years. Our data suggest that organizational factors of neonatal care are responsible for this development. Moderately preterm infants continue to face a considerable risk of
acute respiratory morbidity, which is also predicted by low gestational age, multiparity, Cesarean section, low Apgar score and male sex
