Your doctor will perform fetal heart monitoring to measure your baby’s heart rate and rhythm. Doctors most often perform fetal heart monitoring in the delivery room. It’s critical for your doctor to monitor your baby’s heart rate throughout labor. The timing of your baby’s heartbeats can indicate whether they’re in distress or at physical risk.
Doctors may also use fetal monitoring during the following tests:
- a non-stress test, which measures how the baby’s heart rate changes as they move
- a biophysical profile, which combines a non-stress test and pregnancy ultrasound
- a contraction stress test, which compares the baby’s heart rate with the rate of the mother’s contractions
Doctors can use either external or internal fetal monitoring.
External fetal monitoring
External fetal monitoring involves wrapping a device called a tocodynamometer around your stomach. A tocodynamometer uses high-frequency sound waves to measure your baby’s heart rate. This fetal monitoring method is noninvasive and has no associated complications.
Internal fetal monitoring
Internal fetal monitoring involves inserting a transducer through your cervical opening and placing it on your baby’s scalp. A transducer is a small, patch-like object attached to a wire. The wire connects to a monitor, which displays your baby’s heart rate. Your doctor may perform internal fetal monitoring while assessing the pressure inside your uterus. This allows them to monitor your baby’s heart rate and compare it with your contractions. However, they can only do this type of monitoring once your water breaks and your cervix opens. If these two events haven’t occurred, your doctor can’t perform internal fetal monitoring.
Internal fetal monitoring is usually more accurate than external fetal monitoring. During external monitoring, the accuracy of the heart rate reading may vary depending on where your doctor places the tocodynamometer. The device can also slip out of place easily, which affects its ability to work well. Other times, external monitoring won’t pick up a good signal, and internal monitoring is the only way your doctor can get a true reading of your baby’s heart rate. For these reasons, your doctor may use internal fetal monitoring instead of external fetal monitoring to determine your baby’s heart rate.
Your doctor may choose to perform fetal monitoring during pregnancy or labor if any of the following occurs:
- You have anemia.
- You have a history of heart disease, diabetes, or hyperthyroidism.
- You have oligohydramnios.
- You’re obese.
- You’re carrying more than one baby.
- You go into labor before 37 weeks.
- You go into labor after 42 weeks.
- Your baby moves into a breech position, which means feet or buttocks first
Fetal monitoring usually doesn’t harm babies, but this method has some risks. It’s important that you and your doctor consider these risks before using fetal monitoring.
Risk of infection
Your doctor must insert a gloved hand into the cervix to attach the transducer to perform internal fetal monitoring, This increases the risk of infection because bacteria from the glove, your tissues, or your blood can spread to the baby. Due to this risk, internal fetal monitoring isn’t recommended for women with infections that could potentially spread to the baby.
Risk of fetal injury
During internal fetal monitoring, your doctor tries to place the transducer on the baby’s scalp as gently as possible. In some cases, the transducer might cause some injury to your baby. Examples of potential injuries include bruising and scratching. These markings typically heal quickly without any complications.
Risk of assisted delivery complications
Fetal monitoring gives doctors more information about your baby’s heart rate during labor. This information can be helpful, but it may sometimes create unnecessary concern. In some cases, it might be difficult to determine whether your baby is in true distress or whether the monitor just isn’t reading their heart rate accurately.
When fetal monitoring indicates the baby is distressed, doctors tend to err on the side of caution. They’re more likely to perform an assisted delivery to help prevent complications in the baby. Examples of assisted deliveries include:
- a cesarean delivery, which involves making one incision in your abdomen and another in your uterus to deliver your baby
- a vacuum-assisted delivery, which involves using a vacuum-like device to help ease your baby out of the birth canal
- a forceps-assisted delivery, which involves using large, curved tongs to gently pull your baby out of the birth canal
While these delivery methods are widely used and may be necessary, any extra interventions increase the risk of complications.
For the mother, these may include:
- heavy bleeding
- tears or wounds in the genital tract
- injuries to the bladder or urethra
- problems urinating
- a temporary loss of bladder control
- a severe infection
- an adverse reaction to anesthesia or medication
- blood clots
For the baby, these may include:
- breathing problems
- nicks or cuts
- bleeding in the skull
- minor scalp wounds
- a yellowing of the skin and eyes, which is called jaundice
Your doctor should always discuss the risks and benefits of assisted delivery with you before you give birth.
According to the American Academy of Nursing, the risks associated with internal fetal monitoring outweigh the benefits in low-risk pregnancies. These are pregnancies that are considered to be healthy and not at risk for complications. In low-risk pregnancies, the alternative to internal fetal monitoring is called intermittent auscultation. This method involves using a special stethoscope-like instrument to assess a baby’s heartbeat.
In some cases, fetal monitoring may helpful prevent labor complications. Recent research shows that seizures in newborns occurred less often in women who had fetal monitoring than those who didn’t.
What you can do
Fetal monitoring is important to use in certain situations, but it does involve some risk. You should speak with your doctor about these risks and determine whether this method is best for you and your baby.