Abstract: A sensor placement and retention mechanism for use with fetal sensor sites beyond the user's reach are disclosed. The preferred embodiment of this invention is a fetal pulse oximetry sensor having an active face through which a light source and a light detector operate. The sensor includes a handle that facilitates placement of the active face at a sensor site in a preferred region beyond the transcervical region and beyond the reach of the user. A pair of electrodes--one disposed against the fetus' skin and one exposed to the amniotic fluid--are used to confirm that the sensor is firmly in place on the fetus. In an optional sensor retention feature, a self-inflating bladder presses the active face of the sensor against the fetus' skin to optically couple the sensor with the tissue at the sensor site.

Abstract: An intrauterine pulse oximetry apparatus and method are provided to measure fetal blood oxygen saturation at sites in a preferred region on the fetus. The sensor of the apparatus is attached to a stiff cable which can be inserted into the uterus past the presenting part and transcervical region of the fetus. The cable may have visual and tactile markings by which the user, without seeing or feeling the sensor, can guide it to an appropriate site on the fetus.

Abstract: A first light emitting element directs light through a first region of tissue, a second light emitting element directs light through a second region of tissue that is spatially distinct from the first region of tissue, and a photodetector detects light traveling through the first and second regions. First and second oxygen saturation values are calculated from the amount of light detected from the first and second regions of tissue, respectively. A difference calculating unit calculates a difference value which represents how much the first oxygen saturation value differs from the second oxygen saturation value, and a comparator compares the difference value to a threshold value. A threshold indicating signal is provided when the difference value has a selected mathematical relationship (e.g., less than or equal) to the threshold value.