Special Tests for Monitoring Foetal Health
Foetal monitoring is the procedure used to assess the rate and rhythm of the foetal heart and determine the foetus’s health. It is generally recommended during late pregnancy and labour.
The average heart rate of the foetus lies between 110 and 160 beats per minute, which can vary up to 5-25 beats per minute. The heart rate may vary as the foetus responds to the uterine conditions, but an abnormal pattern may indicate problems such as the lack of oxygen supplied to the foetus.
The foetal heart can be monitored by two methods:
External monitoring: uses the placement of the device on the mothers’ abdomen so that the foetal heartbeat can be heard and recorded. External monitoring can be done to:
- Track the baby's heart rate during rest and movement
- Measure the frequency and duration of contractions during labour and delivery
- Detect premature labour
- Monitor the baby's health if certain problems are suspected
- Monitor the placenta (membrane lining the womb and enveloping the foetus) and ensure that the baby gets enough oxygen
- Monitor for delayed foetal growth, if you have hypertension, diabetes or you have been pregnant for more than 41 weeks
Internal monitoring: foetal heart rate is monitored by placing an electronic device directly on the scalp of the foetus. Internal monitoring can be done to:
- Determine if the baby can be harmed due to stress during labour
- Measure the duration and strength of labour contractions
You may have to eat a meal before the procedure if the foetal heart rate monitoring is combined with other monitoring procedures, as digestion of food increases the foetal activity. If you smoke, you will have to stop smoking a few hours prior to the external monitoring test to prevent a drop in your baby’s activity. The amniotic membrane (fluid-filled sac surrounding the foetus) will be broken and the cervix (neck-like passage opening into the uterus) is dilated to gain access to the foetal scalp.
The foetal heart monitoring involves the use of external or internal monitoring procedures. At times, both procedures can be combined by using an internal sensor to measure the baby’s heart rate and an external sensor to measure your contractions.
External monitoring procedure
External monitoring of the foetal heart can be performed after 20 weeks of pregnancy. The steps include:
- You will be asked to lie on your back. A clear gel will be applied on your abdomen.
- Your doctor will use a Doppler ultrasound device (uses sound waves to create an image of the womb) and move the transducer (sensor) around your abdomen to locate the foetal heartbeat.
- Continuous electronic monitoring can be done by securing the transducer in place with the help of an elastic belt.
- The choice of continuous or intermittent monitoring of the foetal heart rate during labour will depend on your condition and the condition of the foetus.
- The heartbeat can be detected with the help of a Doppler or an electronic monitor.
- A pattern of the heart rate will be displayed on a computer screen and can be printed.
- After the procedure is completed, the gel will be wiped off, and you will be allowed to get out of bed.
Internal monitoring procedure
Internal monitoring procedure is performed during labour. The steps include:
- You will lie on the labour bed with support provided for your feet and legs (as for a pelvic exam).
- Your doctor will conduct a vaginal exam to check if the cervix has sufficiently dilated.
- The amniotic sac will then be broken with an instrument, and its contents will flow out through your vagina.
- Once the doctor determines the head of the foetus with a gloved hand, a plastic electrode will be inserted into your vagina which will guide a spiral wire, which will be placed on the foetal scalp.
- The wires of the electrode will be held around your thigh with a band and will be connected to the monitor.
- The electrode will be removed after the birth of the baby.
External monitoring does not require any specific care, but following the internal monitoring procedure, the site of the electrode on the new-born baby will be checked for the presence of bruises, tears or infection. An antiseptic solution will be used to clean the site of the electrode on the foetus. Depending on your situation, you can resume normal activities and diet unless you are advised otherwise.
Risks and Complications
As with any procedure, foetal monitoring involves certain risks and complications. The outcome of the procedures may be affected by factors such as obesity of the mother, foetal or mother’s position, inadequate dilation of cervix, amniotic sac is not broken or excessive amniotic fluid. Foetal monitoring may cause an increase in caesarean, forceps or vacuum deliveries.
The foetal scalp may get infected and bruised with internal foetal monitoring. It is not advised for HIV positive mothers because of the chances of transferring the infection to the foetus. If you have any concerns, it is best to discuss them with your doctor prior to the procedure.