What is CTG?
Let us first break the term- Cardio-Toco-Graphy.
Upon decoding each fragment we get, Cardio which means heart (as we all know); Toco is a prefix term derived from the Greek word Tokos meaning labor or child birth, and Graphy means graphical representation. So, basically, Cardiotocography is a graphical recording of fetal heart beat and uterine contractions during pregnancy. The machine used to conduct this test is called Cardiotocograph or Electronic Fetal Monitor. The graph looks somewhat like an ECG.
Why is CTG done?
It is done to assess the fetal well being before and during the labor.
How is CTG done?
The mother is asked to lie down on the bed on her back. The machine is brought close to the mother’s bed. It has two transducers. These transducers are based on Doppler ultrasound mechanism. Both the transducers can function externally and internally.
External recording can be done continuously or intermittently. For external recording, first of all the doctor tries to find out the location of the fetal heart with the help of a fetal stethoscope or with the help of a hand held portable Doppler. One transducer is placed on the fetal heart location with the help of some jelly to pick the fetal heart rate. The other transducer is placed on the fundus of the uterus which is identified by mere palpation of the abdomen by the doctor. This transducer records the uterine contractions. A crepe bandage like strap is used to fix both the transducer on to the abdomen. The mother is also given a button which she has to press every time she feels a fetal movement.
Internal recording is done only when labor has progressed and there is some cervical dilatation. A pressure catheter is inserted into the uterine cavity via the vagina and cervix. A scalp electrode is attached to presenting fetal scalp after rupture of the membranes.
When is CTG done?
It is a method of fetal surveillance carried out in the third trimester mostly towards the term and during labor.
When a continuous external electronic fetal monitoring or CTG for 30 minutes is done in late pregnancy i.e. after 32 weeks, it is known as NON-STRESS TEST as there is no stress of labor. In this test, an increase in fetal heart rate with fetal movements is observed and counted upon as a healthy fetus. Sometimes if the fetus is in non-REM sleep and not showing any movements during the recording, vibroacoustic stimulation is given to bring the fetus to REM sleep and initiate fetal movements.
During labor it is done in case there is maternal hypertension, previous caesarean delivery, induced labor, premature rupture of membrane, multiple pregnancy, abnormal fetal heart rate heard through stethoscope. Mostly external monitoring is done in normal cases. Internal monitoring is done only when a complicacy is anticipated in the course of an already progressing normal vaginal delivery.
How does it help the doctor in decision making?
While lying in the labor room with the transducers tied to your abdomen, you may hear terms like acceleration and deceleration. They are nothing but increase in fetal heart rate and decrease in fetal heart rate in response to fetal movements or uterine contractions and relaxations. So you need not panic or be anxious about them. From the graph doctor acquires information about frequency, duration and intensity of uterine contractions along with the changes in fetal heart rate. A first time mom may take 12 to 24 hours to deliver by normal or induced labor. Hence this monitoring becomes necessary to actively assess the fetal well being and progress of the labor until a significant cervical dilatation has occurred. Any abnormality or complicacy or fetal distress faced during monitoring, the doctor can immediately proceed for a lower segment c-section.