External measurement means taping or strapping the two sensors to the abdominal wall. The heart ultrasonic sensor, similar to a Doppler fetal monitor, overlays the fetal heart. The pressure-sensitive contraction transducer, called a tocodynamometer (toco), measures the tension of the maternal 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 and/or stored on a computer for later reference. Use of CTG and a computer network allows continual remote surveillance: a single nurse, midwife, or physician can watch the CTG traces of multiple patients simultaneously, via a computer station.
Use of this machine during labor is called a stress test. When introduced, this practice was expected to reduce the incidence of fetal demise in labor and make for a reduction in cerebral palsy (CP). Its use became almost universal for hospital births in the U.S. In recent years there has been some controversy as to the utility of the cardiotocograph in low-risk pregnancies, and the related belief that over-reliance on the test has led to increased misdiagnoses of fetal distress and hence increased (and possibly unnecessary) cesarean deliveries.
Biophysical profile is another test associated with CTG. It is often done when the non stress test is non reactive.
A randomised clinical trial on cardiotocography plus fetal blood sampling versus cardiotocography plus ST-analysis of the fetal electrocardiogram (STAN.sup.[R].sup.) for intrapartum monitoring.(Study protocol)
Jul 26, 2007; Authors: Michelle EMH Westerhuis (corresponding author) ; Karel GM Moons ; Erik van Beek ; Saskia M Bijvoet ; Addy P...
THE VALUE OF CARDIOTOCOGRAPHY IN PREDICTING FETAL OUTCOME IN WOMEN WHO PRESENT WITH DECREASED FETAL MOVEMENT
May 01, 2006; Background: Maternal perception of decreased fetal movement causes concern in late pregnancy and is a common presenting complaint...