An optical measuring device having features that contribute to increased safety and ease of use include a mechanism to keep the sensor within an introducer tube during storage and insertion, and to expose a portion of the sensor only when the sensor is applied to the unborn baby and a rotating feature whereby if a torque applied on the sensor exceeds a first predetermined amount, the sensor rotates and a disengaging feature whereby the sensor detaches from insertion rod if a pull off force exceeds a second predetermined amount the rotating and disengaging features being independent of one another.
