Cardiotocography
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In medicine (obstetrics) cardiotocography (CTG) is a technical means of recording (-graphy) the fetal heartbeat (cardio-) and the uterine contractions (-toco-) during childbirth. CTG can be used to identify signs of fetal distress.
Recordings are done by two separate electrodes, one for the measurement of the fetal pulse and a second one for the contractions.
External measurement means taping or strapping the electrodes to the abdominal wall, with the heart electrode overlying the fetal heart and the contraction electrode measuring the tension of the abdominal wall, an indirect measure of the intrauterine pressure.
Internal measurement requires a certain degree of cervical dilatation, as it involves inserting a pressure catheter into the uterine cavity, as well as attaching a scalp electrode to the child's head to adequately measure the pulse. Internal measurement is more precise, and might be preferable when a complicated childbirth is expected.
A typical CTG reading is printed on paper or stored on a computer terminal for later reference.