Purpose and Background: This project aims to increase knowledge about how maternal stress during pregnancy affects children's development and genetic expression. The mother's influence on fetal development during pregnancy is significant. Epidemiological studies show that children exposed to prenatal maternal stress have an increased risk of poorer physical and mental health later in life. The biological mechanisms underlying this are still unclear. Stress hormones produced by the mother during pregnancy likely cross the placenta and, in this way, are transferred to the child, where they influence the child's development. The best current method to measure human stress response is to assess the hypothalamic-pituitary-adrenal (HPA) axis activity by measuring cortisol levels. These levels have a natural variation throughout the day and are affected by situational, psychological, or physical stressors. The most commonly used methods for measuring cortisol concentrations are from saliva, blood, or urine. Hair has long been used as a substrate to measure environmental factors, medications, or toxins. Recently, it has been shown that cortisol measurements in hair reflect both stress events and self-perceived stress, thus serving as a measure of retrospective stress. Recent studies indicate that environmental influences during pregnancy alter the child's genetic expression through epigenetic mechanisms. This likely explains the molecular link between "inheritance" and "environment." The epigenetic effects of prenatal stress are well-documented in animal studies, but in humans, there are still few studies showing how environmental factors during pregnancy affect children's epigenetic expression. A sub-study of the project "Little in Norway". Research Method: The project is part of the Little-in-Norway study (LiN study). The LiN study is a longitudinal survey to increase knowledge about pre- and postnatal risk factors that may affect children's development. In the LiN study, biological material and psychological data are collected from around 1000 infants andtheir families from pregnancy to 18 months. I will analyze hair cortisol levels in mothers during pregnancy. This is to study how mothers' hair cortisol levels correlate with mothers' self-perceived stress levels. Participants will then be divided into two groups: one group where the mother has high hair cortisol levels during pregnancy and one group where the mother has a low level. Saliva samples taken from the children at six weeks will be analyzed to see if they have different epigenetic expressions. Subsequently, saliva samples from the children taken at the age of 6 weeks and 12 months will be compared to study how stress in the first year of life affects children's epigenetic expression. Practical Research Implications: This project provides a unique opportunity to develop new knowledge about underlying biological mechanisms in relation to risk factors that affect children's development. The increased understanding can open up for earlier prevention, intervention, and individualized treatment of pathological developmental paths.
