Amniotic Fluid Pressure during Pregnancy

Intrauterine pressure was measured, at the time of diagnostic amniocentesis or cordocentesis, in 200 pregnancies at 10-38 weeks' gestation. Mean pressure decreased exponentially with gestation from 9 mm Hg at 10 weeks reaching a plateau of 5 mm Hg at 30 weeks. These findings are compatible with Laplace's law of pressure in spheroids.