fetal monitoring

Fetal Monitoring in Labor

The purpose of fetal monitoring in labor is to keep a regular check that the process is progressing normally. By such checks, any difficulties and problems, such as fetal distress, can be detected at an early stage.

FETAL HEART MONITORS

One of the best ways of telling whether the fetus is coping with the strain of labor is to listen to its heart beat. Traditionally, this is done with a fetal stethoscope-a hollow metal tube, wider at one find than the other, which is placed on the mother’s abdomen over the position of the fetal back. When the midwife places her ear against the other find she can hear the fetal heart, can count its rate and check that the beat is regular.

The modern fetal heart monitor ‘listens’ to the baby’s heart either by means of an ultrasound head placed on the mother’s abdomen, or by fetal monitoringmeans of a tiny wire clip attached through the cervix on to the fetal scalp. This picks up electrical impulses from the fetal heart through the scalp skin. The sound waves or electrical impulses are then fed into the monitor which automatically records the heart rate and displays it as a flashing light, or beating sound or by writing a continuous record on a moving reel of paper, plus onto a screen.

This latter method of continuous fetal heart recording is the most popular because it enables the obstetrician to see how the heart rate varies during labor and especially during and after contractions. The contractions themselves can be recorded through a simple pressure recorder strapped on to the mother’s abdomen and displayed on the same monitor.

Normally the baby’s heart rate is between 110 and 180 beats per minute. There is a constant small variation in rate, called beat-to-beat variation, and the rate reacts only slightly or not at all to the uterine contractions. A slow rate, below 110 beats a minute, or a high rate, above 180 beats per minute, a loss of beat-to-beat variation which gives a rather flat trace, or a sharp and prolonged drop in rate during and after a contraction, may all indicate fetal distress.

Fetal monitoring is particularly valuable in monitoring fetal well-being in ‘at risk’ cases, such as when the mother has toxaemia. With the object of making labor as safe as possible for the fetus, many obstetric units monitor most cases, including normal cases. Apart from the inconvenience of the abdominal belt and the wires which are attached to the machine, the mother suffers no discomfort. The sight of the trace of the baby’s heart, displayed by the monitor by the side of her bed, is very reassuring.

INTRAVENOUS DRIPS

An intravenous drip, for feeding liquid into the mother’s vein, is often used in labor. It provides a way of giving the mother fluid if she is unable to drink and glucose if she is unable to eat. (Fluids and food are often restricted in labor to avoid nausea and vomiting). The other use for the drip is to give drugs to the mother.

Oxytocin, also called Syntocinon, is a preparation of a natural hormone which makes the uterus contract. It may be given by drip for this purpose if labor is slow, or during or following an induction.

Prostaglandins are sometimes used for the same purpose. Sometimes, too, a small attachment is put on to the drip. This counts the rate of the drops given per minute and automatically adjusts the rate to keep it constant.

FETAL BLOOD SAMPLES

Occasionally when it is thought that the fetus is becoming distressed through lack of oxygen, a sample of blood may be taken from its scalp. In order to do this, a hollow tube, an amnioscope, is passed into the vagina, through the cervix and placed against the baby’s head. By passing a special instrument down this tube, a very small quantity of the baby’s blood can be obtained and tested. The actual measurement that is made is that of the acidity (pH) of the blood because this gives a good indication of the actual blood oxygen level.

The procedure does not harm the fetus in any way and is not uncomfortable for the mother. It provides valuable information about the baby’s well-being and is very important in the diagnosis of fetal distress.

PARTOGRAPH

This is another addition to fetal monitoring, consisting of a simple chart that is used in many labor wards to show the progress of labor. The dilatation of the cervix and the descent of the fetal head are recorded on the chart after each examination. By comparing the rate of dilatation of the cervix with a normal graph, the patient’s progress can be assessed and a rough estimate made about when delivery is likely to take place.