Perinatal risk factors. With special reference to intrauterine growth retardation and neonatal respiratory adaptation.

Intrauterine growth retardation (IUGR) and neonatal respiratory disorders (RD) are two dominating problems in perinatal medicine. The aims of this study were to analyze the possibilities of selecting groups of pregnant women with increased risk of either problem, to analyze the relationship between IUGR and neonatal respiratory disorders and to evaluate the influence on neonatal respiratory adaptation of different events during delivery. For these purposes epidemiological methods were mainly used but in paper V an animal model was applied. In the whole population of pregnant women attending the antenatal clinic of the department during a six month period the items which had the best discriminating power between normal and IUGR pregnancies were selected. These eight items (previous infants less than or equal to 2,500 g, hypertension, kidney diseases, smoking, bleeding with or without uterine contractions, insufficient increase of weight, girth or fundal height) were used as a scoring system. With a risk population of 7%, all IUGR cases were included. The IUGR infants constituted 34% of the risk group. For one year all newborns of mothers living in Göteborg were screened prospectively for signs of respiratory disorders. It was not possible to indicate antenatally pregnancies with increased risks of neonatal respiratory disturbances. Preterm small for gestational age (SGA) infants were found to have the same risk of RD as non-SGA infants. Full term SGA infants had a higher incidence of RD, which could not be explained by their higher incidence of cesarean sections (CS) and low Apgar scores. In preterm infants and in full term infants after CS the relation between rupture-delivery interval and risk for RD was "u-shaped". There was a higher incidence of RD if delivery was immediately at rupture than a few hours up to 36 h later. After more than 36 h the risk increased again. Consequently there seems to be no advantage in postponing delivery more than 36 h after ROM. The impact of CTG (cardiotocography) pattern on RD during delivery, was analyzed in two subgroups of infants (greater than or equal to 37 weeks, delivered by CS). Infants with ominous CTG patterns were unexpectedly found to have a reduced incidence of RD, 6% compared to 21% in infants with normal patterns. A possible explanation could be that "intrauterine stress" might exert a positive effect on neonatal respiratory adaptation.(ABSTRACT TRUNCATED AT 400 WORDS)