Like in the full immersion, studied in the context of diving, immersion in water causes a cascade of events with hemodynamic and hormonal consequences.

First, immersion leads to a relative hypervolemia by venous redistribution and then 40-60 minutes later, hypovolemia by stimulating diuresis.

Dilatation bath is helpful in relieving moderate pain the first stage of obstetrical labor.

However, when the labor progresses, the dilatation bath is no longer sufficient and epidural analgesia remains the only effective method to control pain.

Used before the realization of an epidural analgesia, dilatation bath could affect blood volume and thus worsen the hemodynamic consequences of the sympathetic block that is linked to the installation of sensory block of the epidural analgesia in the parturient (severe prolonged maternal hypotension that can cause a decrease of the placental perfusion and fetal distress).

Before beginning a study in pregnant women, it seems essential to study the hemodynamic consequences of the dilatation bath in a comparable population of volunteers healthy young women and out of the obstetrical context.

Inclusion Criteria:

Healthy female volunteers aged 18 to 45 years

Exclusion Criteria:

• pregnancy
• menopause (confirmed for at least 12 weeks)
• breastfeeding
• Proteinuria> 2 cross on the dipstick
• Glycosuria > 2 cross on the dipstick
• subject with no empty stomach for at least 8 hours
• Taking medication in the week before the test affecting diuresis, production of antidiuretic hormone or on the cardiovascular system: paracetamol, nonsteroidal anti-inflammatory Alcohol intake the day before the tes