When Should You Hear a Heartbeat in the First Trimester of Pregnancy?

by Piper Li

Similar to feeling you baby's kicking movements, hearing his heartbeat can help reassure you that everything is going fine with your pregnancy. Normally heard during the first trimester of pregnancy, this amazing sound may help bring home the reality of impending parenthood. This experience also provides one of earliest, audible contacts you and your husband have with your growing child. Knowing when you might first hear your baby's heartbeat allows you to prepare for this big moment and invite others to be present at this exciting, prenatal appointment.

Early Development

Your baby's heart begins developing soon after conception. Although you may not be able to hear a beating heart yet, a vaginal ultrasound performed about 6 weeks after your last period may indicate the presence of a growing embryo. At this point, your baby can measure between 2 and 4 millimeters between his head and rump. Even though it is still early in your first trimester, your doctor may notice a regular fluttering movement, signaling the beating of a tiny heart.

Tools and Devices

In addition to the vaginal ultrasound, which provides the earliest method for detecting your baby's heartbeat, your doctor may listen with an external fetal monitor. Placed on your abdomen, this instrument bounces harmless sound waves off your baby's heart, making an audible sound. Although it won't pick up early fetal heart tones, a standard stethoscope allows you to listen to your baby's heartbeat as he grows inside your uterus.

Listen Carefully

With careful placement of the ultrasound device, you may first hear the heartbeat around nine or 10 weeks after your last period started. Your weight may also affect your chances of hearing the heartbeat at this early stage. Expect to hear the heartbeat by about 12 weeks, near the end of your first trimester. Keep in mind that the location of the placenta and the thickness of your abdominal fat may affect the results. Using a traditional stethoscope, you won't hear your baby's heartbeat until the second trimester, sometime around 20 weeks after your last period.

Heart Tones

Although you might like listening to your baby's heartbeat for personal enjoyment, your doctor can use the sounds to help monitor the health of your developing baby. Fetal heart rates normally fall between 120 and 160 beats each minute.

Safety Issues

Although some new mothers may worry about the long-term effects of using external fetal monitors, listening to your baby's heartbeat with one of these devices causes no known medical risks.

About the Author

Piper Li, a professional freelance writer, began writing in 1989. Her articles appear online at Biz Mojo, Walden University and various other websites. She is the co-editor for "Kansas Women: Focus on Health." With a bachelor's degree in journalism from Mesa State, Li enjoys writing about health, horticulture and business management.

Photo Credits

  • pregnant #10 image by Adam Borkowski from Fotolia.com