Fetal heartbeat: early pregnancy signs

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You may be able to see the beating of cells in the heart tube for the first time when you’re about¬†6 weeks pregnant¬†if you have an early¬†ultrasound¬†exam.

October 24th 2022  |  Originally posted on: October 18th 2022

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When does a baby have a heartbeat?

At 5 to 6 weeks of pregnancy, there’s a flickering of cells within the embryo’s torso. This flickering is the developing heart tube.

At this point, the heart isn’t the four-chambered organ we’re familiar with. It’s a tube-shaped structure that has a lot of developing to do. The heart tube bends and twists to eventually form the heart, including its chambers.

Because the heart isn’t yet developed, the American College of Obstetrics and Gynecologists (ACOG) defines this movement as “cardiac activity” rather than a heartbeat.

“What pregnant people may hear or see is the ultrasound machine translating electronic impulses that signify fetal cardiac activity into the sound that we recognize as a heartbeat,” ACOG states. The group recommends waiting until the heart is fully formed before using the term “heartbeat.”

A baby’s heart¬†is one of the first structures to form, because it’s needed to deliver oxygenated blood and nutrients to other developing organs.

Some of the important steps in heart development are:

  • The heart tube twists and bends into an S shape, and the bottom of the tube moves up to form the two upper heart chambers (atria).
  • The middle of the tube forms the two lower chambers (ventricles).
  • Valves form between the ventricles and the aorta (large blood vessel) and pulmonary artery.
  • At about¬†10 weeks¬†to¬†12 weeks, the heart is formed.
  • Small blood vessels form and fill with blood.
  • At birth, the opening between the two atria closes. Your baby is now getting oxygen from their lungs and not from¬†the placenta.

What does a fetal heartbeat sound like?

Many women say that the beating of their baby’s tiny heart sounds like galloping horses. The embryonic and fetal heartbeat is fast, about 110 to 160 beats per minutes.

If you hear a whooshing noise, that’s not the heartbeat ‚Äď it’s probably because of movement or the monitor traveling past your placenta. Also, if you hear two heartbeats, don’t assume¬†you’re having twins. You’re likely hearing your own heartbeat in the background.

If the heart rate of the embryo or fetus is healthy, it’s a sign that development is progressing normally. The chances of a miscarriage once you see or hear a heartbeat are less than 10 percent (at 6 weeks) and less than 1 percent at 9 weeks.

If you don’t have a first-trimester ultrasound, you’ll probably first hear your baby’s heart with a handheld Doppler at a regular¬†prenatal visit. Your caregiver may be able to find cardiac activity with a handheld Doppler as early as 10 weeks,

but the timing depends on a number of factors, including the position of your uterus, your belly shape, and how full (or empty) your bladder is.

What if my provider can't detect a heartbeat?

If your doctor or midwife doesn’t find your baby’s heartbeat on your first-trimester ultrasound right away, it could be because:

  • It’s too early in your pregnancy. Your¬†due date¬†may be off. (This can happen, especially if your¬†menstrual cycle¬†was irregular.) Your provider will schedule another visit in a week or two.
  • You have a¬†retroverted¬†uterus. Because of the position of your uterus, the baby can be just a little further away and harder to detect.
  • You’re¬†overweight. Extra padding between the ultrasound wand and the baby may make it harder to detect the heartbeat.
  • Miscarriage. If there’s no heartbeat when expected (and ultrasound measurements confirm the age) or if cardiac activity was detected and now isn’t, this may be a sign of miscarriage.
  • Ectopic pregnancy. In this case, an ultrasound wouldn’t pick up heart motion in the uterus because there’s no embryo there. Although ectopic pregnancies are never viable, they can sometimes develop enough to have heart motion. An ectopic pregnancy is a surgical emergency that can be fatal if not treated quickly.

How will i usually hear my baby's heartbeat?

Your provider will check your baby’s heart rate with a¬†fetal Doppler (a handheld ultrasound monitor) at each prenatal visit after about 10 weeks.

The procedure is completely painless. Your doctor or midwife will cover the device with ultrasound gel and move it around on your belly until they find a spot where the heartbeat can be detected. The Doppler sends and receives sound waves that safely bounce off your insides, including your baby’s heart. The returning sound waves are processed and amplified by the device so you and your provider can hear the heartbeat.

You can rent or buy a Doppler for home use. However, some experts think a home Doppler isn’t a good idea.

That’s because it can take considerable training and practice to find and correctly identify a baby’s heartbeat. You may not be able to hear the heartbeat ‚Äď not because of an issue with your baby, but due to user error. It’s also possible to hear the sound of blood flowing through the placenta or your own blood vessels and mistake it for a heartbeat.

There are better ways to monitor your baby, such as paying attention to¬†your baby’s movements¬†and attending all of your prenatal appointments.

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Sources: 

Miles, K. 20th July 2022. When Can I hear my Baby’s heartbeat? From Babycenter. https://www.babycenter.com/pregnancy/health-and-safety/when-can-i-hear-my-babys-heartbeat_10349811 [Accessed October 2022]

ACOG. Undated. ACOG Guide to Language and Abortion. The American College of Obstetricians and Gynecologists. https://www.acog.org/contact/media-center/abortion-language-guide [Accessed July 2022]

Johns Hopkins Medicine. Undated. Fetal heart monitoring. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/fetal-heart-monitoring [Accessed July 2022]

MayoClinic. 2020. Fetal development: The 1st trimester. https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/prenatal-care/art-20045302 [Accessed July 2022]

MedicalNewsToday. 2020. When does a fetus have a heartbeat? https://www.medicalnewstoday.com/articles/when-does-a-fetus-have-a-heartbeat [Accessed July 2022]

Napolitano R et al. 2015. First-trimester detection of fetal anomalies, in Twining’s Textbook of Fetal Abnormalities (Third Edition).¬†https://www.sciencedirect.com/topics/medicine-and-dentistry/gestational-sac¬†[Accessed July 2022]

Rettner R. 2019. Is a ‘Fetal heartbeat’ really a heartbeat at 6 weeks? LiveScience.¬†https://www.livescience.com/65501-fetal-heartbeat-at-6-weeks-explained.html¬†[Accessed July 2022]

Steinburg SP et al. 2013. What is the ‘normal’ fetal heart rate?¬†Peer J¬†1:e82.¬†https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3678114/¬†[Accessed July 2022]

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