Definition Foetal monitoring is the recording of the baby's heart rate and the mother's contractions during labour. Devices are connected to the mother's abdomen and to the baby.
This is done in two ways:
External monitoring uses external belts around the mother's abdomen.
Internal monitoring involves placing a monitor electrode on the baby's scalp. A thin tube or catheter is also inserted into the uterus via the vagina to monitor contractions.
Who is a candidate for the test? The contractions of the uterus during labour decrease the amount of blood flowing to the placenta, the organ that normally attaches to the uterus, connecting the developing foetus to the mother and supplies nutrition and oxygen to the foetus. Contractions also decrease the blood flow to the foetal umbilical cord, which inserts into the developing baby's belly button and connects the foetus to the placenta. The decreased blood flow cuts down on the amount of oxygen getting to the baby. Labour and delivery can be risky to the foetus under normal conditions, but presents even more risk if the placenta is not functioning fully. In most hospital settings, the majority of women in labour undergo foetal monitoring to ensure a good outcome.
Conditions that require foetal monitoring include:
intrauterine growth retardation, a condition in which the foetus is not growing at an appropriate rate
past due pregnancy, of more than 42 weeks
preeclampsia, a toxic condition of pregnancy that may cause increased blood pressure, excessive swelling in the arms or legs, abnormal kidney function and disturbances in vision
eclampsia, a condition in which seizures develop in a woman with preeclampsia
use of epidural anaesthesia, a type of anaesthesia in which the analgesia is given directly into the compartment that contains the spinal cord
use of drugs given to cause labour and delivery. These include oxytocin and prostaglandins.
suspected foetal distress
presence of green amniotic fluid due to meconium, or foetal bowel movement, which may cause meconium aspiration syndrome.
Foetal monitoring is also used to evaluate the strength of uterine contractions in cases such as:
preterm or early labour
placenta abruptio, a condition in which the placenta detaches from the wall of the uterus at an inappropriately early time
failure of labour to progress
How is the test performed? Only external foetal monitoring is conducted if the fluid-filled membrane surrounding the foetus, known as the amniotic sac, has not broken. This is more common in early term or pre-term labour. The woman should lie on her left side if possible. This allows the maximum amount of blood to reach the infant. Two belts are placed around the abdomen. One belt will monitor the baby's heartbeat. The other measures the strength and frequency of uterine contractions.
Internal monitors can be placed once the amniotic sac has broken. Internal monitors provide a more accurate picture of the progress of labour. Internal monitoring involves two devices. The first is a small wire placed directly on the baby's scalp, called the foetal scalp electrode. It measures the baby's heart rate. The second is an intrauterine pressure catheter. This is a narrow plastic tube inserted through the vagina, past the cervix and into the uterus. It is attached to a pressure gauge that measures the timing and strength of the uterus' contractions. Both of these devices are attached to a computerised foetal monitor. This instrument converts the heart rate and uterine contractions into a readable graph chart.
What is involved in preparation for the test? A woman should discuss the use of foetal monitoring with her doctor during her antenatal visits in order to understand the risks and benefits of the testing.
What do the test results mean? Foetal heart rate during labour varies. The normal range is from 120 to 160 beats per minute. Heartbeat speeds up and slows down slightly during and after a contraction. Abnormal heartbeat patterns may indicate:
foetal distress. It can be either an ongoing problem or develop suddenly.
fever in either the woman or the foetus. This usually indicates an infection.
an umbilical cord wrapped around the baby's neck or compressed during a contraction.
inability of the foetus to withstand the stress of labour.
Abnormal uterine contraction patterns may indicate:
slow progress of labour. This may be due to dehydration or insufficient amounts ofoxytocin, a medication used to cause labour and delivery.
abnormally prolonged and intense contractions. This may be due to placenta abruptio or the use of too much oxytocin.
irritable uterus, or a uterus that contracts too frequently due to irritation. This may be the result of premature labour or fever.
Any of these results may require an immediate caesarean section or other form of intervention to prevent serious complication for mother or baby.
Author: Eva Martin, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 6/06/2005 Contributors Potential conflict of interest information for reviewers available on request
