A wearable antenna is described, for wirelessly receiving sensor data generated by an implantable sensor device implanted in a uterus, the wearable antenna, in use, extending around the waist of the wearer's body, and having a downwardly extending portion for location at the front of the wearer's body. In this way, an improved electromagnetic interaction between the wearable antenna and the implantable sensor can be achieved. Further, the wearable antenna may have an undulating shape around at least a portion of the wearer's waist, to permit expansion and contraction of the wearable antenna about the wearer's waist.
