The aim of this study was to show how a pregnant woman's body changes during pregnancy and how she reacts to exercise in pregnancy. Through the explained changes and adaptations of different organ systems, an insight into the organism is given, with an emphasis on the respiratory system. The first part describes the general anatomical and physiological changes in pregnancy, while the second part analyzes in detail the respiratory system and its parameters. Furthermore, some of the respiratory disorders in pregnancy such as dyspnoea, pulmonary hypertension, sleep-disordered breathing and asthma are listed. The last chapter deals precisely with exercise in pregnancy. The benefits of physical activity are highlighted, as well as the contraindications and complications that can occur before and after exercise. Adaptations of different organ systems while exercising and engaging in different activities were analyzed, as well as adjustments of general physiology of pregnant women and fetus during exercise in pregnancy. Recommendations and basic guidelines for exercise in pregnancy are also included.