Determinants of perinatal outcomes in Norway: 1982-2020

Abstract

Perinatal outcomes are important indicators of maternal and fetal health on a population level, as well as important predictors of later health on an individual level. Although much is known about predictors of perinatal outcomes, there are still unknown mechanisms affecting fetal growth, the pregnancy duration and risk of complications such as preeclampsia. As a larger proportion of pregnancies in modern societies are to older couples, with a higher likelihood of adverse lifestyle factors and more frequently conceived by assisted reproductive technologies, there is a need to assess how this may impact fetal and maternal health. The aim of this thesis was to study possible predictors of perinatal outcomes in a contemporary setting in Norway, and to assess their implications for fetal growth, gestational duration and risk of pregnancy complications. This was achieved using large Norwegian registries to assess factors on a population-level basis, as well as a large Norwegian pregnancy cohort to assess a factor not available from the registries. Known predictors of birthweight could not explain a temporal trend among live term births to Scandinavian-born women in Norway with an increase in the 1990’s followed by a decrease in the 2000’s. This suggests that there are still undiscovered predictors of birthweight that are not associated with adverse neonatal health. Maternal HbA1c levels in mid-pregnancy were associated with fetal growth parameters, gestational duration, and risk of preeclampsia. This suggests that HbA1c levels reflect glycaemic control also in pregnancy, which could be of clinical importance. Perinatal outcomes were similar in women and men who were themselves conceived by assisted reproductive technologies, although they had fewer pregnancies by the end of follow-up compared to their peers. Longer follow-up time to complete the reproductive periods are needed for more in-depth assessment.