When Does The Heartbeat Of A Child Form?

Since you found out you were pregnant, one of the first milestones you’ve likely eagerly awaited is hearing the thump, thump of your baby’s heartbeat. It’s one of the most reassuring sounds there is. And though it probably will sound the same to you from checkup to checkup, there are big changes happening to the heart and circulatory system every week of your pregnancy!

When does your baby have a heartbeat?

By week 5, a baby’s heart tube begins to beat spontaneously, though you quite can’t hear it yet. 

If you get a first-trimester ultrasound (sometime between weeks 6 and 9 of pregnancy), your practitioner or a trained sonographer will get a visual on your baby to check that his heart is beating. The ultrasound will also confirm your estimated due date along with how many babies you’re carrying.

When can you hear a baby’s heartbeat?

You may hear your baby’s heartbeat for the first time around week 10 of pregnancy if you receive an ultrasound, although the timing can vary a bit. 

Can’t hear it yet? Don’t worry. It likely just means that your shy guy is hiding in the corner of your uterus or has his back facing out, making it hard for the Doppler to find its target. At your next appointment, your practitioner will check to make sure everything is okay. Chances are, you’ll be able to hear your baby’s heartbeat then.

Normal fetal heart rate

By 6 weeks, your baby’s heart is beating 110 times a minute. In just two more weeks, the fetal heart rate will rise to 150 to 170 beats a minute. That’s about twice as fast as yours!

By week 9 or 10, your baby’s heart beats about 170 beats per minute — a rate that will slow from here on out. At around week 20, it’ll go down to around 140 beats per minute. 

During labor, a normal fetal heart rate can span from 110 to 160 beats per minute, although brief variations outside of this range can occur for a variety of (often perfectly normal) reasons. 

When can you hear your baby’s heartbeat with Doppler?

You’ll most likely hear your baby’s heartbeat with a Doppler at around the 12 week mark, but you may hear it as early as week 10. Your doctor or midwife will place this handheld ultrasound device on your belly to amplify the pitter-patter of the heart. 

Keep in mind that experts including the Food and Drug Administration (FDA) warn against using at-home fetal Dopplers unless you’re under the supervision of a medical professional.

That’s in part because these devices aren’t as sophisticated as the ones that doctors use, so they may not pick up on a baby’s heartbeat — leading to an unnecessary scare. Plus, it can be hard to use an at-home Doppler properly without training. You could, for example, mistake your own heartbeat for your baby’s. 

When can you hear a baby’s heartbeat with a stethoscope?

By around week 20 of pregnancy, you can often hear your baby’s heartbeat with a stethoscope — about eight to 10 weeks after it’s detectable by Doppler.

How your baby’s heart and circulatory system develop

Fetal heart development starts early on in pregnancy and your baby’s ticker continues to change even after birth as he adjusts from the womb to the world. 

First trimester development

By week 4, a distinct blood vessel has formed inside your embryo, which will soon develop into your baby’s heart and circulatory (blood) system. At week 5, the preliminary structures that make up your baby’s heart begin spontaneously beating. 

In these early stages, it resembles a tube that twists and divides to eventually form the heart and valves (which open and close to release blood from the heart to the body). Precursor blood vessels also begin to form in the embryo during the first few weeks.

By week 6, your baby’s heart has four hollow chambers, each with an entrance and an exit to allow blood to flow in and out. Exciting circulatory developments continue at 12 weeks, when your baby’s bone marrow begins busily producing blood cells. 

Second trimester development

By 17 weeks, the fetal brain has begun to regulate the heartbeat in preparation for life in the outside world. (Up until this point, the heart beaten spontaneously.)

Capillaries also form at an exponential rate during the second trimester. These teeny-tiny blood vessels deliver oxygenated blood to the tissues in your baby’s body and then recycle deoxygenated blood back into the circulatory system. 

During your second trimester ultrasound, your doctor will check the structure of your baby’s heart and look for any congenital heart defects.

If your doc needs a better listen and view of your baby’s heart, he or she may recommend a fetal echocardiogram between 18 and 24 weeks of pregnancy. You’ll want to make sure you get one if you have a family history of congenital heart defects, or if you personally have diabetes, phenylketonuria or an autoimmune disease.

Third trimester development

Baby’s circulatory system will continue to grow slowly and steadily during the last trimester, so that by 40 weeks it’s ready for its debut outside the womb.

How the fetal heart works

While the fetal circulatory system develops rapidly throughout pregnancy, it actually works quite differently in utero than it does once your baby is born. 

Since babies don’t breathe in utero, the lungs don’t actually function before birth. Until then, his developing circulatory system relies on the umbilical cord for a steady supply of oxygen- and nutrient-rich blood. Umbilical arteries and veins transport what your baby needs from you to him, then carry unoxygenated blood and waste products back to you for removal.

Most of the physical differences between the fetal and adult heart serve the purpose of directing blood away from baby’s lungs, which simply aren’t needed in utero. The fetal heart has: 

  • Three shunts. These shortcuts direct blood away from the lungs and the liver.
  • A ductus arteriosus. This fetal artery connects the pulmonary artery (which will eventually bring blood from the heart to the lungs) and the aorta (which will bring blood from the heart to the body). It detours blood away from the lungs in utero.
  • A foramen ovale. This for-the-womb-only opening between the upper chambers of the heart again shunts blood away from the lungs.

Once your baby is born, all of these fetal differences start to go away or disappear completely. When the umbilical cord is cut, his lungs take in air, the fetal circulation system is switched off and the shunts begin to close. All systems are a go! From the time you get your positive pregnancy test, your baby’s heart is developing and changing rapidly. To help ensure his ticker gets the healthiest start possible, take your prenatal vitamin throughout pregnancy, quit smoking or vaping (if you currently light up) and avoid alcohol and recreational drugs.

culled from whattoexpect.com by Colleen de Bellefonds

Leave a Reply

Your email address will not be published. Required fields are marked *