Despite the increasing progress in the use of instruments to assess emotional health in the perinatal and puerperal periods, it is emphasized that most of the tools used do not have psychometric evidence for the population of pregnant women. The Depression, Anxiety and Stress Scale (DASS-21) enables the measurement of anxiety, stress, and depression levels, simultaneously. The study aimed to assess the internal consistency of the DASS-21, the convergent validity of the scale in relation to the State-Trait Anxiety Inventory (STAI), the Beck Depression Inventory -second edition (BDI-II), and the Perceived Stress Scale (PSS) and the stability of the evaluations in a range of up to 12 weeks. Fifty-three (first evaluation) and 35 pregnant women (second evaluation) participated in the research. The scale showed adequate internal consistency, stability, and convergence rates for the investigated population. The DASS-21 can help practitioners and researchers of health, providing agility in the diagnosis of unfavorable emotional indicators in different gestational periods.