A pneumatic tocodynamometer (“pTOCO”) (10) having a guard-ring (13) with a thin elastic membrane (18) stretched across a shallow spherical depression (12) trapping a small volume of air in the center of the guard-ring (13). A pressure transducer (17) may be molded into the body 11 of the pTOCO (10). In an alternative embodiment, the air volume beneath the membrane (18) of the pTOCO (10) may be connected via a low volume air conduit (14, 15) to a separate pressure transducer (16).
1. A pneumatic tocodynamometer, comprising: a sensor body having a planar lower surface; said planar lower surface comprising a rigid guard-ring and an elastic membrane covering a depression centered in said rigid guard-ring; a closed interior air volume defined by said depression and said elastic membrane; and a pressure transducer communicating with said closed interior air volume.