For most parents, the experience of hearing their unborn baby’s heartbeat for the first time and seeing the image on the ultrasound is an exciting moment. Hearing the steady rhythm of the fetal heartbeat can make parents realize they are truly having a baby in a short time. It also brings a sense of peace as they see their child is healthy and developing like he or she should.
The embryonic heart starts beating 22 days after conception, but at this stage, the fetal heartbeat is too small to hear. Sometimes, however, the fetal heartbeat can be seen as a flickering in the chest on an ultrasound screen when the ultrasound is done as early as four weeks after conception.
During doctor visits, the obstetrician practitioner will use a Doppler instrument for listening to the fetal heartbeat. The Doppler bounces harmless sound waves off the baby’s heart. The way the sound comes back is affected by motion, and the beating heart creates a change in the sound waves that the Doppler picks up and records.
To measure the fetal heartbeat, the practitioner counts the heartbeats for a full minute, or counts for fifteen seconds and multiplies by four. Some fetal Dopplers provide the fetal heartbeat rate. An average adult’s heart rate is less than 100 beats per minute, but a fetal heartbeat is normally between 120 and 160 beats per minute. The practitioner can tell the difference between the mother’s heartbeat and the fetal heartbeat because of this difference between the two.
Although there are myths and rumors about fetal heartbeat rates being different for boys and girls, the medical community says a fast or slow heartbeat depends on the individual baby, and not the gender. The sound of the fetal heartbeat depends on the distance the Doppler instrument is from the fetal heart. During a twin pregnancy, it can be difficult to determine the fetal heartbeats of each baby. The practitioner will listen at different points and angles on the uterus to try to determine the rates for each baby. If only one heartbeat can be heard, an ultrasound can be done to show the fetal heartbeat of the twins.
Some companies now sell Dopppler-like instruments so that parents can listen to the fetal heartbeat outside of the doctor’s office. However, most parents are not trained in the intricacies of finding the fetal heartbeat, and often become alarmed when the heartbeat cannot be found or the heart seems slower than it was in the doctor’s office. When the baby is 20 weeks along, it is developed enough so that one can hear the fetal heartbeat with a stethoscope. Stethoscopes cost far less than the Doppler instruments, which usually sell for around $500.
The fetal heartbeat can be heard best when the instrument is pressed over the baby’s back, which is often the firmest part of the baby when pressing around the abdomen. If one is overweight or the placenta is on the front of the uterus, the fetal heartbeat can be more difficult to hear.
By Virginia Zignego