Birth-characteristics, hospitalisations, and childbearing Epidemiological studies based on Swedish register data

Sammanfattning: In the past decades there has been an improvement in the medical treatment of children born preterm or with reduced foetal growth. This has resulted in a much higher survival rate of these children, but also in a higher number of surviving children with chronic conditions. These changes have, in turn, increased interest in investigating the connection between birth-characteristics and outcomes in later life. The overall aim of the present thesis was to study the relations between birth-characteristics, subsequent hospitalisations, and childbearing by means of data available in Swedish population-based registries.The study population in this thesis consisted of women (and men in Paper III) born in 1973-75 according to the Medical Birth Register and the Total Population Register. Information available in other registries, such as the Hospital Discharge Register, was obtained by individual record linkage.In Paper I, 148,281 women, alive and living in Sweden at 13 years of age, were included. Of the women, 4.1% were born preterm and 5.4% were born small for gestational age, and approximately 30% of all women had given birth between 13 and 27 years of age. We found that reduced foetal growth and possibly preterm birth were related to the likelihood of giving birth during the study period. The intergenerational effects of preterm birth and reduced foetal growth were investigated in Paper II and the study population consisted of 38,720 mother-offspring pairs. An intergenerational effect of reduced foetal growth was found, and reduced foetal growth in the mother also increased the risk for preterm birth in the child.Paper III was concerned with 304,275 men and women living in Sweden at 13 years of age. Of these men and women, 30% were hospitalised during adolescence and early adulthood (i.e. between 12 and 23 years of age). We found that men and women born small for gestational age or preterm were more likely to be hospitalised, and that those born small for gestational age seemed to be more at risk compared to those born preterm. Finally, in Paper IV, the relation between hospitalisations during adolescence and the likelihood of giving birth was studied in 142,998 women living in Sweden at 20 years of age. We found that a majority of the causes of hospitalisation during adolescence were positively connected to the likelihood of giving birth between 20 and 27 years of age. The relations presented in Papers I-IV were evident although socio-economic characteristics were adjusted for.