Many studies have been supporting the positive effects of an active lifestyle concerning the prevention and treatment of pregnancy-related complications and health problems, such as gestational diabetes, gestational hypertension, obesity, low back pain, urinary incontinence, anxiety or depression, as well as regarding its effectiveness in maintaining fitness and functionality, and in improving postpartum recovery. Practice and clinical guidelines have become increasingly popular tools for synthesizing evidence-based information to assist practitioners and patients/participants in making decisions related to starting or continuing physical activity. Despite this knowledge, most women still do not receive proper guidance on how to exercise during pregnancy or after childbirth, and the prevalence of physical inactivity is still high among pregnant and postpartum women. On the other hand, the COVID-19 pandemic has highlighted the need for virtual approaches in health interventions, but few studies have addressed the effectiveness of such interventions. This study is about the benefits of exercising during pregnancy in terms of maternal physical activity, fitness, and healthy lifestyle parameters. After the first visit to the doctor, pregnant women without absolute contraindications to exercise will be invited to participate in a multi-site (fitness center, university, or hospital) prenatal exercise program delivered either in person or online by qualified exercise physiologists. The exercise intervention will follow international evidence-based guidelines. It includes aerobic, coordination, strength, postural, stretching, and pelvic floor exercises, organized in two weekly sessions lasting 60 minutes each. Pregnant women will be asked to answer questionnaires about physical activity, fitness, and healthy lifestyle parameters (sleep, diet, stress) twice: before starting the exercise program and after completing 12 weeks of the program. The same procedure applies to basic fitness field tests (e.g., to assess balance, flexibility, strength, cardiorespiratory fitness, etc.). Participants will have access to the free Active Pregnancy Guide (including recommendations for walking, dancing, swimming, etc.). On other days of the week, they can follow specific workouts on the YouTube channel (@GravidezAtiva-ActivePregnancy). Researchers will test whether the exercise program is beneficial in maintaining or improving maternal physical activity and fitness levels and healthy lifestyle parameters after 12 weeks. Moreover, researchers will compare which exercise mode (in-person or virtual) is better or similar. Participants will also be asked about their satisfaction with the intervention and educational resources. Participation and resources will be free. All participants will benefit from the exercise intervention. The study's results will contribute to knowledge on this topic, inform future exercise recommendations for pregnant women, and inform public health strategies.