To Örebro University

Placental function and foetal growth can be influenced by environmental factors or maternal medical conditions. The aim of this thesis was to characterise biological pathways in the placenta of importance for normal and impaired foetal growth, and to investigate whether maternal SARS-CoV-2 infection affects placental protein expression or is clinically associated with aberrant newborn birth weight. In study I, placental microRNA and protein expression profiles were characterised in pregnancies with normal newborn birth weights. Study II explored microRNA expression in placentas from pregnancies complicated by small-for-gestational-age (SGA) newborns. In study III, the impact of maternal SARS-CoV-2 infection on placental levels of inflammatory and cardiovascular proteins was investigated. In study IV, potential associations between maternal SARS-CoV-2 infection with aberrant birth weight, was investigated using Swedish registers. Inflammatory response, lipid metabolism, and neurodevelopment were highlighted as key biological processes in the healthy term placenta, suggesting that these pathways may be particularly susceptible to environmental insults and maternal disease. In SGA placentas, eight microRNAs were found to be differentially expressed and connected with inflammation and the insulin/IGF system. These findings indicate that subclinical inflammation, through disturbances in the insulin/IGF system, may be involved in unexplained SGA births. For pregnancies complicated by maternal SARS-CoV-2 infection, no persistent changes were seen in placental levels of inflammatory or cardiovascular proteins in term birth. Further, in the general pregnant population, maternal SARS-CoV-2 infection was not associated with an increased risk of SGA or abnormal birth weight at term, regardless of infection timing or severity.