The aim. of fetal monitoring is to make sure that any harm which might threaten the fetus in the uterus can be recognised in time so that the baby can be removed in time from it's unfavorable environment or the harmful. influence can be removed. This applies to both during pregnancy and during labour.
In 1953, while working in Lewisham Hospital, Southeast London, Gunn and Wood reported "The amplification and recording of fetal heart sounds" in the proceedings of the Royal Society of Medicine. In 1958 Hon pioneered electronic fetal monitering in the US.A. This setthe scene for the fetal monitor by Hammacher and Hewlett Packard in 1968,
The enduring challenge of Obstetrics lies in the need to care for People simultaneously. One the mother who can express her feelings, answer our questions and allow us to examine her. The other, the fetus' (the baby) is hidden . far from our view and such information as we can obtain must be gained to resort to indirect methods and .hence the
development of tests of fetal well being. soon to be followed by Sonicaid in the UK. Thus what we have today is the Electronic Fetal MQnitor or Cardiotocograph. Electronic Fetal Monitering in the UK. is known as Antenatal (during pregnancy) and Intra-partum (during labour) Cardiotocographs whereas in the US. cardiotocographs during pregnancy are referred t . as Non-Stress Tests, a term The machine consists of an ultrasonic transducer which uses the principle of sound waves getting altered by a moving structure, in this case the baby's heart and blood flowing through it and records the baby's heartbeat which gets translated into an external tracing much like as that of an adult Electrocardiogram (ECG). A direct ECG of the baby can also be obtained by applying an electrode to the baby which the doctor uses during labour under certain clinical circumstances. The activity of the uterus is detected by another transducer. As the uterus ontracts and moves forward, a sensor pin attached to a strain gauge is pushed in by the shape of the mother's tummy. The change in electric current is amplified and recorded on the paper. Direct data of this activity within uterus can also be detected by a catheter inserted within the uterus which is rarely necessary. The tracing of the baby gets recorded on the upper half of the strip of paper and activity of the uterus on the bottom half.
The principle of this test is that movement of the baby is accompanied' by a transient increas or acceleration of the baby's heart rate. This forms the basis for the Non-Stress Test or the fetal acceleration test.
When this test is, done dring pregnancy, each time the rhovement of the baby is felt by the mother, she presses a button to record the instant of movement on the 'saine moving paper strip that the heart rate is recptded upon.The test is generally considered, normal or Reactive when two or more movements of the baby are accompanied by increase or acceleration of the baby's heart rate of 15 beats/min for atleast 15 seconds duration within a 20 minute recording period. This indicates a healthy baby. A Non-Reactive tracing is one without acceptable fetal heart rate increase or accelerations over a 40 minute period. This indicates that the baby may be sick within ,the womb and' the doctor will take appropriate steps for 'the same either by asking for more tests or consider delivery. Observations reported to date imply that an increase of the fetal heart rate during and immediately after fetal movements most often, but certainly not always indicates that the fetus will survive for atleast one week provided the mother'scondition remains stable.
Reactive nonstress test. Notice increase of fetal heart rate to more than 15 beats per minute for longer than 15 second following fetal movements, indicated by the vertic marks on the lower part oj the recording
During labour the same principle is used but since the mother cannot feel the baby move due to contractions the doctor will also interpret the tracing obtained from the baby in response to contractions of labour to see how well it is coping up with the stress of labour.