Monitoring Your Baby’s Heart Rate

By: Bradley G. Goldberg, M.D.

During most of your obstetric office visits, and throughout your labor process, the heart rate of your baby will be monitored. This process is referred to as “fetal heart rate monitoring”.

The baby’s heart rate can usually be heard for the first time around the 12th week of pregnancy, although this varies. A healthy baby’s heart rate is faster than an adult, and is normally between 110 – 160 beats per minute. The rate changes periodically in response to fetal movement, and sometimes in response to fetal stress.

There are two ways to listen for the heart rate. First is the more traditional approach using a device called a “fetoscope”. The fetoscope is a device similar to a stethoscope, which is placed on the abdomen. This is an older, less sensitive technique and is not commonly used anymore. The second technique is electronic and utilizes a handheld “Doppler” ultrasound unit. This is much more sensitive and can detect the fetal heart rate much earlier in the pregnancy.

The fetal heart rate will also be monitored during labor. This can be done either intermittently (listening every few minutes) or in a continuous fashion. Most modern hospitals use the continuous monitoring during labor. Usually this is done with an external device similar to the hand held Doppler used on office visits which is fastened to your abdomen with a Velcro belt.

In certain circumstances it may be necessary to use internal monitoring with a fetal scalp electrode. The electrode is a small wire that is applied just under the skin on the baby’s scalp (similar to having a splinter). Instead of “listening” for the baby’s heart rate like the Doppler device, the electrode picks up the electrical signal of the heart rate, giving a more precise reading. It is removed at delivery and usually the application site is not even obvious, however there is a rare chance of complications such as skin infection, which is why we do not use it routinely.

Although fetal heart rate monitoring cannot guarantee a perfect outcome, it can often help to identify problems during the labor process. When you are on the fetal monitor during labor the doctors and labor nurses look for “reactivity” which are the reassuring accelerations in the heartbeat that indicate a healthy baby. If more concerning, or “non-reassuring”, patterns are noted a Cesarean section or other rapid delivery method may be performed.

Other types of monitoring are currently being investigated. Most promising is a device that can measure the oxygenation status of the baby, although this is years away from being considered standard of care.
 

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