Mood during pregnancy: Trends, structure, and invariance by gestational day.

Mood dynamics during pregnancy are important in understanding a critical period of human development, and also as a model for biopsychosocial stress processes. Here, in four large samples of smartphone app respondents (differentiated by time period and number of responses), we modeled mood for each gestational day during the pregnancy period. We aimed to delineate patterns of changes in mood across pregnancy, as well as potential changes in measurement properties across the period. Results indicated that three prominent mood factors - positivity, distress, and irritability - could account for responses in this period, and that changes in measurement properties of mood items across pregnancy were small in magnitude. Mean irritability increased, and positivity decreased, in the first trimester before reversing in direction; there was also some evidence for previously reported U-shaped trends in mood, where negative mood is greatest early in pregnancy, decreases, and then increases again. Results help characterize mood processes at a detailed level during a critical period, and point to directions for future research to explicate causes and effects of mood changes during this time.