Water immersion and changes in the foetoplacental and uteroplacental circulation: an observational study with the case as its own control.

Objective: To evaluate the effect of immersion into water on maternal blood pressure, amount of amniotic fluid and on the foetoplacental- and uteroplacental circulation in healthy women with an uncomplicated singleton pregnancy. Methods: Twenty-five healthy women were included. Recordings of blood pressure, deepest vertical pocket of amniotic fluid and pulsatility index (PI) measured by Doppler in the umbilical and uterine arteries were obtained. The participants were immersed into water and the measurements were repeated after 5 and 25 min in water and again 15 and 30 min post immersion. Results: The amount of amniotic fluid increased significantly (p<0.001), and the maternal blood pressure decreased significantly during immersion (p<0.001). There was no significant effect of immersion on either umbilical-or uterine artery PI. All changes returned toward baseline-level within 30 min after immersion. Conclusions: Immersion into water increases the amount of amniotic fluid and decreases the maternal blood pressure. Immersion into water has no significant effect on either the foetoplacental or uteroplacental circulation. Further studies are needed in order to explore the effect of immersion in pregnancies complicated by a dysfunctional placenta.