The investigators aim to evaluate the effect of long-term moderate intensity physical activity during pregnancy in maternal and fetal cardiovascular system. A randomized clinical trial was designed with two groups (Study group and Control Group).

Physical activity (PA) enhances not only physical but also mental health.PA contributes to the prevention of a variety of diseases in general population including hypertension, diabetes mellitus, stress, and depression. Nevertheless, pregnancy is a time period that various changes take place in a woman's body. Those alterations might be either facilitators or barriers for conducting PA during pregnancy.

When it comes to pregnancy several benefits have been associated with PA for both mother and fetus; such as low gestational weight gain, lower incidence of gestational diabetes mellitus (GDM), better management of Pre-eclampsia and post-partum weight retention. Moreover, PA improves mental health in pregnant women, while recent studies have revealed that physical exercise during pregnancy can improve oxidative stress, inflammation and endothelial function. The vast majority of Obstetricians & Gynecologists recommend that pregnant women should be urged to start or continue doing physical activity in the absence of contraindications. To be more specific, pregnant women should do at least 150 minutes of moderate intensity PA weekly. However, several studies support that pregnant women all over the world does not meet those recommendations. Relevant evidence of published literature are scarce regarding the alterations on maternal and fetal cardiovascular system due to chronic exercise .

Thus, investigators aim to evaluate the effect of long-term moderate intensity PA in maternal and fetal cardiovascular system. Thus, a randomized clinical trial with two groups (study group-control group) was designed. The study group includes pregnant women during the 1st trimester that will undergo moderate intensity PA, while the control group includes pregnant women that will receive the routine antenatal care. Participants will be followed up until 6 months postpartum.

To be more specific, all participants will receive a pedometer to record their daily steps from the first trimester until the postpartum period. The intervention group will additional receive detailed recommendations for 30 minutes of moderate intensity exercise at least 4-5 times per week (if not daily) and brochures with relevant information will be administrated as well. Moreover, brochures with dietary recommendations during pregnancy will be given to all participants.

Three routine antenatal ultrasound scans at 11-13+6 , 20-24, and 32-36 gestational weeks will be performed. Maternal Uterine Dopplers will be assessed at every scan, while fetal Dopplers will be done at 2nd and 3rd trimester. Maternal cardiovascular assessment will take place at 1st trimester, 3rd trimester and postpartum with transthoracic echocardiography, ophthalmic artery Doppler, Flow Mediated Dilatation and Arterial Stiffness . Fetal heart function will be assessed at 2nd and 3rd trimester. Evaluation of the infants' heart will also be performed at 6 months postpartum. A questionnaire evaluating mental health known as Depression-Anxiety and Stress Scale 21 (DASS-21) in pregnant women will be administered during the 1st and 3rd trimester. Maternal body fat measurements will take place at each trimester and postpartum. In addition fat composition of both the fetus will be evaluated by ultrasound before the delivery and the newborn within 48 hours following birth. Maternal blood sample will be collected during 1st trimester, 3rd trimester and postpartum and blood sample from the umbilical cord during labour, to assess several parameters.

All participants will be fully informed about the purpose of the study and will be included only after signing the Informed Consent Form. All data collected will be confidential and only accessible to members of the research team. These data will be coded according to GDPR. The clinical implementation of this study will be according to the International Code of Medical Ethics of the World Medical Association (Declaration of Helsinki), and all participants submitted a written informed consent since a detailed description of all aspects and the objectives of the study are explained and fully understood. The ethical committee of the University Hospital of Ioannina approved this study (decision number: 3/30-01-2024; date of approval; 30 January 2024).

Inclusion Criteria:

• Pregnant women during 1st trimester, who had the routine dating scan at 11-13+6 gestational weeks [also known as Nuchal translucency (NT) scan] and the uterine arteries (UtA) PI assessment

Exclusion Criteria:

• Diabetes Mellitus (Type I or II)
• Maternal age < 18 years old
• Body Mass Index (BMI) > 40
• Contraindications for PA: Multiple Pregnancies, Vaginal Bleeding, Hypertension or Gestational Hypertension, Uncontrolled Thyroid Diseases, Cardiovascular Diseases (e.g. valvular diseases, congenital heart diseases, cardiomyopathies, atrial fibrillation, coronary heart disease) or respiratory system diseases (asthma, chronic obstructive pulmonary disease) or systemic disease (cancer, autoimmune diseases) or several other diseases considered to be barriers for PA during pregnancy.