Fetal Monitoring During Labor

Fetal Monitoring Labor

Monitoring your baby’s heart rate during labor, along with the duration and frequency of your contractions, helps your doctor assess how well your baby is doing. Fetal monitoring measures the response of your baby’s heart to your contractions.

The average heart rate of a baby during labor is between 110 and 160 beats  per minute, with a variation of about 5 to 25 beats. The baby’s heart rate can vary in response to  the mother’s contractions, or as the result of medication given to her during labor.

A steady heart rate with minor variations means labor is proceeding normally while changes in the normal pattern may indicate a problem and a need for medical intervention.

During the first part of labor the baby’s heart rate will be checked about every half hour. Later on it will be checked about every 15 minutes but it may be monitored more often if there is a problem during labor or if you had a high risk pregnancy.

Intermittent or continuous monitoring: advantages and disadvantages

Your baby’s heart rate may be monitored externally or internally, intermittently or continuously during your labor. Several factors influence the decision and labor can develop in unexpected ways. Most hospitals have a centralized fetal monitoring system that allows nurses to continuously track the baby’s heart rate at their station and notify a doctor of any significant changes.

Each type of monitoring has advantages and disadvantages

External monitoring is the most commonly used type of monitoring, especially in low risk pregnancies. It can be intermittent or continuous.

One advantage of intermittent monitoring is the mother’s ability to walk during labor, which is recommended as a way to ease the pain of contractions.

If the heart rate is only measured intermittently, a  doctor or nurse will measure the baby’s heartbeat using a handheld device, similar to a stethoscope. You may be familiar with this device, the Doppler transducer, since it was likely used to monitor your baby during prenatal visits. Since the heartbeat is only monitored during set times, this intermittent method allows the laboring mother to move around.

Labor may start with only intermittent monitoring but then switch to continuous monitoring

A high risk pregnancy dictates continuous monitoring. For example, a mother who has preeclampsia or type 1 diabetes would be considered high risk. Any concerns about the baby’s development might also warrant continuous monitoring, as does opting for epidural pain relief.

Continuous external monitoring works by attaching two sensors to your abdomen with elastic bands. The sensors monitor the baby’s heartbeat and note how long your contractions last. The pattern of your contractions and your baby’s heartbeat appear on a screen and a printout. The advantage of this type of monitoring is that it becomes immediately apparent if your baby is having a problem.

The disadvantage of such monitoring is that it limits  a laboring mother’s mobility since she has to stay near the monitor. Studies have shown that continuous monitoring can prevent neonatal seizures and other complications but use has led to more cesarean deliveries,  since doctors prefer to be cautious.

Internal monitoring

If a doctor can’t get a satisfactory reading from external monitoring, internal monitoring may be recommended. For example, if the mother is obese, it can make an external reading less reliable.

Internal monitoring involves placing a thin wire through your vagina on to the baby’s body, usually the scalp, since it’s closest to the cervix. This method of monitoring can only be used if your amniotic sac or waters have broken. A catheter may also be inserted to measure uterine contractions.

There is a slight risk of infection or bruising on the baby’s scalp with internal monitoring but the attachment site is usually treated with an anesthetic immediately after birth.

What happens if your baby’s heart rate is abnormal?

The results of fetal monitoring are read and interpreted by a doctor, who will then decide if an intervention is needed. An abnormal heart rate does not necessarily mean there is a problem.

However, if a baby is not getting enough oxygen, doctors can note changes based on the heart rate, as well as a slowing down of  fetal movement. If a baby appears to be in distress and not getting enough oxygen, doctors are likely to schedule an immediate cesarean.

As your due date approaches, you may want to discuss what happens during labor with your doctor or midwife. It can also help to learn what the hospital or birthing center’s policies are on common labor practices.

Joan MacDonald
Joan Vos MacDonald has written about health and fitness for newspapers, magazines and websites. She is a member of the National Association of Science Writers and the author of two books on health-related topics, "Tobacco and Nicotine Dangers," for young adults, and "High Fit Home," a design book about fitness and architecture. She lives in upstate New York near her children and grandchildren.

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