A study has found that pregnant woman who had bigger fluctuations in stress had infants with more fear, sadness and distress.The study was published in the journal, 'Infancy'.Prior research has found that mothers' distress during pregnancy has been related to infant temperament and behavior, but this is one of the first studies to measure mothers' experience of stress in real time on many occasions, which enables a closer look at whether changes in mothers' stress across pregnancy matter for infant development. “Research often examines stress as a static, unchanging construct -- one that is either high or low, present or absent -- but most of us have a lot of ebbs and flows in our stress depending on what is going on around us,” said lead study author Leigha MacNeill, research assistant professor of medical social sciences at Northwestern University Feinberg School of Medicine and a member of the Northwestern Institute for Innovations in Developmental Sciences (DevSci).