This is a single-centre observational, prospective study carried out at the maternity unit of Dijon CHU. It will include pregnant women with a pre-conception BMI ≥ 30 kg/m² and will evaluate in these patients, the activation and migration capacities of circulating leukocytes and their association with the onset of spontaneous labour. Patients who meet the inclusion criteria will be informed about the study during their consultation at the 7th or 8th month, and their gynecologist will invite them to take part. If the answer is positive, the patients will be seen again at a specific consultation for the study between the 37th and 38the Weeks of amenorrhea at the maternity unit of Dijon CHU. During this consultation, the gynecologist will conduct a medical examination, while the Plurithematic clinical investigation center nurse will take a blood sample (3 x 6ml tubes and 1 x 7ml tube). If labour has not started by 41 Weeks of amenorrhea, the patients will be seen at another consultation (consultation programmed in the usual follow-up of pregnancy) and a second blood sample (1 x 6ml tube and 1 x 7ml) will be taken. The patients will be followed until childbirth and will be split into two groups according to whether or not they gave birth after the onset of spontaneous labour.