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.

INTRODUCTION: Maternal SARS-CoV-2 infection can affect pregnancy outcome, but the placental response to and the effect of timing of infection is not well studied. The aim of this study was to investigate the placental levels of inflammatory and cardiovascular markers in pregnancies complicated by SARS-CoV-2 infection compared to non-infected pregnancies, and to investigate whether there was an association between time point of infection during pregnancy and placental inflammatory and cardiovascular protein levels.

METHODS: Placental samples from a prospectively recruited pregnancy cohort of SARS-CoV-2-infected (n = 53) and non-infected (n = 50) women were analysed for 177 inflammatory and cardiovascular proteins, using an antibody-based proximity extension assay. In the SARS-CoV-2-infected group, half of the women were infected before 20 weeks of gestation, and five women were hospitalised for severe SARS-CoV-2 infection. Single-protein analyses were performed with linear mixed effects models, followed by Benjamini-Hochberg correction for multiple testing. Multi-protein analyses were performed using principal component analysis and machine learning algorithms.

RESULTS: The perinatal outcomes and the placental levels of inflammatory or cardiovascular proteins in women with SARS-CoV-2 infection were similar to those in non-infected women. There were no differences in inflammatory or cardiovascular protein levels between early and late pregnancy SARS-CoV-2 infection, nor any linear correlations between protein levels and gestational age at time of infection.

DISCUSSION: Women with SARS-CoV-2 infection during pregnancy without clinical signs of placental insufficiency have no changes in inflammatory or cardiovascular protein patterns in placenta at time of birth regardless of the timing of the infection.

Introduction: Description of the global expression of microRNAs (miRNAs) and proteins in healthy human term placentas may increase our knowledge of molecular biological pathways that are important for normal fetal growth and development in term pregnancy. The aim of this study was to explore the global expression of miRNAs and proteins, and to point out functions of importance in healthy term placentas.

Materials and methods: Placental samples (n = 19) were identified in a local biobank. All samples were from uncomplicated term pregnancies with vaginal births and healthy, normal weight newborns. Next-generation sequencing and nano-scale liquid chromatographic tandem mass spectrometry were used to analyse miRNA and protein expression, respectively.

Results: A total of 895 mature miRNAs and 6,523 proteins were detected in the placentas, of which 123 miRNAs and 346 proteins were highly abundant. The miRNAs were in high degree mapped to chromosomes 19, 14, and X. Analysis of the highly abundant miRNAs and proteins showed several significantly predicted functions in common, including immune and inflammatory response, lipid metabolism and development of the nervous system.

Discussion: The predicted function inflammatory response may reflect normal vaginal delivery, while lipid metabolism and neurodevelopment may be important processes for the term fetus. The data presented in this study, with complete miRNA and protein findings, will enhance the knowledge base for future research in the field of placental function and pathology.

Introduction: The placenta is an endocrine organ vital to fetal growth. It has multiple functions: pregnancy maintenance, nutrient and oxygen transport to the fetus, and removal of waste products among other functions. MicroRNAs (miRNAs) and proteins are significant mediators of these functions. A description of their global expression in healthy placenta may increase our understanding of the molecular biological pathways that are important for normal fetal growth and development. The aims of this study were to explore the global expression of both miRNAs and proteins in the same samples of human term healthy placenta and to describe involved pathways.

Methods: Nineteen term placenta samples from healthy women with uncomplicated pregnancies were identified in a local sample collection. The samples were derived from uncomplicated vaginal deliveries with healthy normal weight new-borns (5 females). Next generation sequencing and nano-scale liquid chromatographic tandem mass spectrometry were used for the analyses of miRNA and protein expression, respectively. Ingenuity Pathway Analysis was used for functional bioinformatics analyses.

Results: A total of 895 mature miRNAs and 6,523 proteins were detected in the placenta samples, whereof 123 miRNAs and 346 proteins were highly abundant. The miRNAs were in high degree mapped to chromosomes 19, 14 and X. The most abundant proteins served as enzymes (23%), transporters (10%) or transcription regulators (8%). Of the 20 most significant downstream functions for the highly expressed miRNAs and proteins, respectively, eight shared functions were found, namely Cellular function and maintenance, Cell death and survival, Cell-to-cell signaling and interaction, Cellular assembly and organization, Organismal development, Digestive system development and function, Hepatic system development and function, and Inflammatory response.

Discussion: As far as we know, this is the first study presenting both global miRNA and protein expression in the same placenta sample set from healthy term pregnancies. Two of the chromosomes found to have high presence of miRNA genes in the present study are known to contain placenta-specific miRNA clusters (chromosomes 14 and 19), while chromosome X might have been identified here since it has a higher density of miRNA genes than autosomes. The biological functions for the miRNAs and proteins point at basic cellular actions and clearly illustrate that development is an important task during fetal life. Profound knowledge of miRNA and protein expression in healthy placenta can improve the management of aberrant fetal growth and development.

INTRODUCTION: There is limited knowledge on how the SARS-CoV-2 affects pregnancy outcomes. Studies investigating the impact of COVID-19 in early pregnancy are scarce and information on long-term follow-up is lacking.The purpose of this project is to study the impact of COVID-19 on pregnancy outcomes and long-term maternal and child health by: (1) establishing a database and biobank from pregnant women with COVID-19 and presumably non-infected women and their infants and (2) examining how women and their partners experience pregnancy, childbirth and early parenthood in the COVID-19 pandemic.

METHODS AND ANALYSIS: This is a national, multicentre, prospective cohort study involving 27 Swedish maternity units accounting for over 86 000 deliveries/year. Pregnant women are included when they: (1) test positive for SARS-CoV-2 (COVID-19 group) or (2) are non-infected and seek healthcare at one of their routine antenatal visits (screening group). Blood, as well as other biological samples, are collected at different time points during and after pregnancy. Child health up to 4 years of age and parent experience of pregnancy, delivery, early parenthood, healthcare and society in general will be examined using web-based questionnaires based on validated instruments. Short- and long-term health outcomes will be collected from Swedish health registers and the parents' experiences will be studied by performing qualitative interviews.

ETHICS AND DISSEMINATION: Confidentiality aspects such as data encryption and storage comply with the General Data Protection Regulation and with ethical committee requirements. This study has been granted national ethical approval by the Swedish Ethical Review Authority (dnr 2020-02189 and amendments 2020-02848, 2020-05016, 2020-06696 and 2021-00870) and national biobank approval by the Biobank Väst (dnr B2000526:970). Results from the project will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER: NCT04433364.

COVID-19 in pregnancy increases the risk of caesarean section. We present two cases of late gestation pregnant women with severe COVID-19. Both were successfully treated with mechanical ventilation without termination of pregnancy and, following recovery from COVID-19, had vaginal deliveries at term. These two cases demonstrate the possibility of treating pregnant women with severe COVID-19 with mechanical ventilation in the late second and early third trimesters without them having a pre-term delivery. With a multidisciplinary approach, such management could avoid the maternal risks of surgery during a severe infection and, at the same time, enable term birth with a lower risk of neonatal complications.

INTRODUCTION: The molecular mechanisms behind poor foetal growth are not fully known. The aim of this study was to explore global microRNA expression in placentas of infants born small for gestational age (SGA) compared to infants with a normal birth weight (NBW).

METHODS: Placental biopsies from term infants were identified in a biobank and divided into four groups: infants born SGA with (n = 13) or without (n = 9) exposure to low maternal gestational weight gain (GWG) and infants born with NBWs with (n = 20) or without (n = 26) exposure to low GWG. All women and infants were healthy, and no woman smoked during pregnancy. Only vaginal deliveries were included. Next-generation sequencing was performed with single read sequencing of >9 million reads per sample. Differential microRNA expression was analysed using ANOVA for unequal variances (Welch) with multiple testing corrections through the Benjamini-Hochberg method. A fold change >2 and a corrected p value < 0.05 were considered significant. Adjustments for possible confounding factors were made using a linear regression model.

RESULTS: A total of 1870 known, mature human microRNAs were detected in the sample. MiR-3679-5p and miR-193b-3p were significantly upregulated, and miR-379-3p, miR-335-3p, miR-4532, miR-519e-3p, miR-3065-5p, and miR-105-5p were significantly downregulated after adjustment for potential confounding factors in SGA infants with normal GWG compared to infants with NBWs and normal GWG.

DISCUSSION: Infants born unexplained SGA show differential microRNA expression in their placenta. Important pathways for the differentially expressed microRNAs include inflammation and the insulin-IGF system.