Excessive weight gain during pregnancy can promote subsequent obesity or increase pre-existing maternal obesity, lead to complications during pregnancy, such as gestational diabetes, hypertension and pre-pregnancy eclampsia, which affect fetal growth.

What are the determinants of excessive weight gain? The first determinant of excessive weight gain is related to healthy living place and physical activity, noted as "PA". Many meta-analyses have demonstrated the role of PA in gestational weight gain.

The main objective is to study the role of the living environment in the PA practice of pregnant women and to identify the socio-environmental construction contributing to the disparities in the practice of PA in women during their pregnancy. This thesis is based on an innovative approach in France, combining both epidemiology and geography approaches to meet priority research objectives in a public health context. With regard to the general issue "What are the contextual determinants of pregnant women's PA practice beyond their individual characteristics that could explain the disparities in practice according to their socio-economic position?" This question underlies the following assumptions:

i) In addition to their individual characteristics, women with low PA and who have reduced PA during pregnancy reside in a more socio-economically deprived neighborhood.

ii)Beyond the socio-economic dimension, the physical characteristic of the residential place influences the level of PA practice of pregnant women.

iii) The combination of the socio-economic, physical and psychosocial environment contributes to reducing the level of PA among pregnant women.

iv) Pregnant women with an unfavourable living environment and low PA have adverse pregnancy outcomes.

Inclusion Criteria:

• Pregnant women living in the Strasbourg Eurometropolis
• Women performing ultrasound follow-up and giving birth in HUS
• Understanding of the French language
• Patient who has expressed no opposition to the research and/or has signed a consent form in case of collection creation

Exclusion Criteria:

• Refusal to participate in study
• Minor women
• Unable to provide informed information (subject in an emergency, difficulty understanding the subject, etc.)
• Subject under protection of justice
• Subject under guardianship or curatorship
• Obstetric pathologies against-indicating the practice of AP

Pregnant women will be included in the study at the time of their first or second trimester ultrasound in the Hautepierre and CMCO ultrasound department. The period of inclusion should extend from 1 October 2020 to 31 October 2021 with a duration of participation of each subject of 9 months.