Objectives: The aim of this study was to assess perinatal risk factors and the survival of the very preterm infant in comparison with birth beyond 32nd birthweek, as well as health care utilization by mothers and infants in the Northern Health Region of Sweden.
Design: A population-based study was designed of all children (66,646) born in the Northern Health Region of Sweden during 1991-1996 and registered in the Swedish Medical Birth Registry.
Methods: Maternal and perinatal factors of infants born very preterm, that is, at < or =27 and 28-31 weeks of gestation, were analyzed for relative risk (RR), and a 95% confidence interval (CI), and compared with those of infants born 32-36 weeks of gestation.
Results: Of the 66,646 infants registered, 3,493 (5.2%) were born at 32-36 weeks, 394 (0.6%) at 28-31 weeks, and 199 (0.3%) at 22-27 weeks' gestation. No special socio-demographic maternal factors characterized these preterm births. The very preterm infants were more prone to perinatal complications such as premature rupture of the membranes (PROM) (RR=4.13; 95% CI=3.07-5.55), and both PROM and hemorrhage (RR=7.80; 95% CI=3.43-17.72). Infants born very preterm were more often twins, growth-retarded, malformed, and affected by sepsis and respiratory distress. There was significantly better survival of preterm infants born at < or =27 weeks' gestation if their mothers were given tertiary perinatal care. For infants born extremely preterm, survival tended to be better if they were delivered by cesarean section.
Conclusion: The very preterm birth is more often than not a result of a complicated pregnancy. The infant is often sick before birth, and for its survival is highly dependent on the highest level of perinatal care.