Labour and delivery of a baby is a stressful period for parents and even sometimes for the baby. Measuring the heart rate of the baby during pregnancy and labour may identify certain problems in time for medical intervention. During pregnancy and before the onset of labour the midwife or doctor may ask for a test of the heart rate if there is a suspicion of problems.
Certain equipment may be used to measure the heart rate and this is called monitoring. All babies will have fluctuations in heart rate during labour and most of these changes are normal. However certain patterns may signal a problem which may prompt the midwife or doctor to take steps to protect the health of the baby.
Types of monitoring
The heartbeat of the baby may be checked by a simple instrument which looks like a short trumpet that is held against the pregnant tummy. This is called a Pinnard stethoscope (or foetoscope) and can be used by a midwife or doctor to listen to the heartbeat periodically. This method can be used anywhere and does not require electricity or expensive equipment. It may be old-fashioned, but is a very useful and effective way of monitoring.
Modern electronic equipment come in two forms namely Doppler and CTG (cardiotocogram).
A machine using Doppler technology consists of a probe and a receiver. The probe is a device which makes high frequency sound waves which is reflected from the moving heart of the baby and then measured again. Doppler machines may be very simple and report only the rate and rhythm of the beat, but more sophisticated models will provide additional information about blood flow in the umbilical artery. Doppler machines are often used during pregnancy before the onset of labour to evaluate the function of the placenta (afterbirth). Simple Doppler devices (such as Doptone) are commonly used in ante-natal clinics and sometimes during labour as well.
A cardiotocogram measures the heart rate of the baby (cardiogram) and the frequency and intensity of the uterine contractions (tocogram). Two sensors, the size of Marie biscuits, are attached to the pregnant patient with broad elastic bands which are then connected with a cable to a machine. The machine prints a continuous paper report, which indicates the heart rate and contractions. In a minority of women in labour, the external sensors may not “hear” well enough and the doctor may attach a small electrode to the baby’s scalp to record the heart rate. This is referred to as internal monitoring.
When to monitor:
It is not always necessary to monitor the baby all the time during labour. Most normal labours can be safely checked by intermittent monitoring. If there are special situations, constant monitoring may be needed.
What is normal?
It is normal for the heart rate to vary between 110 and 160 beats a minute. The rate is much faster than that of the mother. A normal pattern will have a degree of variation. During contractions the rate and pattern of the heart may change and certain patterns may suggest a problem.
What happens if the tests are abnormal?
During pregnancy before the onset of labour an abnormal test will usually lead to some form of intervention if it is serious, or closer surveillance if the problem is mild.
During labour a short period of abnormality can be managed with one of the following:
- You may be asked to change your position (usually to lie on your side) to increase blood flow to the uterus
- You may be given extra oxygen through a mask
- You may receive medicine to stop the contractions and relax the uterus
- You may get extra fluid through a drip
If the problem persists or is of a serious nature, your doctor may suggest an immediate or urgent delivery of the baby. Sometimes a Caesarean section is the best option but a forceps or suction (ventouse) delivery will be used in the right circumstances.