A person's 1st heartbeat.
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Since you found out you were pregnant, one of the first milestones you’ve likely eagerly been awaiting 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!
When your baby's heart begins developing.
Even though at 4 weeks pregnant that sweet, sweet heartbeat hasn’t yet arrived, a distinct blood vessel has formed inside your embryo, which will soon develop into your baby’s heart and circulatory (blood) system. In the early stages, the heart resembles a tube that twists and divides, eventually forming the heart and valves (which open and close to release blood from the heart to the body). In fact, by week 5, the heart tube begins to beat spontaneously, though you can't hear it. During those first few weeks, precursor blood vessels also begin to form in the embryo.
When you’ll hear baby’s heartbeat for the first time
By 6 weeks, your baby’s heart — now beating 110 times a minute — has four hollow chambers, each with an entrance and an exit to allow blood to flow in and out of each chamber. In just two more weeks, that number will rise to 150-170 beats a minute. That’s about twice as fast as yours!
With all of this growth, the chances are strong that you’ll be able to hear your baby’s heartbeat for the very first time around week 9 or week 10 of pregnancy. It will be about 170 beats per minutes by this time, a rate that will slow from here on out. Your doctor or midwife will place a handheld ultrasound device called a Doppler on your belly to amplify the telltale sound.
More on Fetal Development
Fetal Development: Baby’s Bones and Skeletal System
Fetal Development: Baby's Nervous System and Brain
Fetal Development: Baby’s Digestive System
Fetal Development: Baby's Hair, Skin & Nails
Can’t hear it yet? Don’t worry. It just means that your shy guy or gal is hiding in the corner of your uterus or has his or her back facing out, making it hard for the Doppler to find its target. In a few weeks (or at your next visit), the miraculous sound of your baby's heartbeat is certain to be audible for your listening pleasure. And your practitioner will check to make sure everything is okay, so feel free to ask any questions if you're concerned.
Ultrasound & congenital heart defects
Sometime between 6 weeks and 9 weeks of pregnancy, your practitioner (and/or a trained sonographer) will perform your first trimester ultrasound. It will not only confirm your pregnancy and estimated due date (along with how many babies you're carrying and the placement of the fetus) but also check that the heart is beating.
During your second trimester ultrasound, or 20-week anatomy scan, your doctor will check the structure of baby's heart and whether any problems (known as congenital heart defects) can be detected. About 36,000 babies (or 9 of every 1,000 infants) are born every year with a congenital heart defect, making this the most common type of major birth disorder. Although there is no medicine that can cure a heart defect in utero, and some defects can't be detected until after birth, a diagnosis during pregnancy helps doctors decide where to deliver your baby (usually in a large medical center, where pediatric cardiac care is available immediately after birth). Sometimes the issue needs to be handled with surgery right after birth, while other defects may need to be fixed at an older age or treated with medications. If your practitioner detects a fetal heart rhythm problem, she may prescribe medication to decrease the odds that your baby will be born early.
The good news is that the majority of congenital heart defects can be repaired and managed if detected early and treated promptly. Kids with congenital heart disease need to visit a cardiologist periodically throughout childhood and their adult lives.
You can hear baby’s heartbeat with a stethoscope!
Exciting circulatory developments continue at 12 weeks, when baby-to-be’s bone marrow begins busily producing blood cells. By 17 weeks, the fetal brain begins to regulate the heartbeat in preparation for supporting baby in the outside world. (Up until this point, the heart has been beating spontaneously.) In three more weeks, by around week 20, you can hear your baby’s heartbeat with a stethoscope.
If your doc needs a better listen (and a view), she may recommend that you get a fetal echocardiogram, a special ultrasound that evaluates the fetal heart, between 18 and 24 weeks. (If you have a family history of congenital heart defects, or if you personally have diabetes, phenylketonuria or autoimmune disease, make sure you get one.)
By now, baby's heart is beating at about 140 beats per minute. By the close of week 25, capillaries (the smallest blood vessels) are forming and filling with blood. Capillaries move oxygenated blood via the heart’s arteries to tissues throughout baby's body and then feed deoxygenated blood back to the lungs – making these teeny-tiny blood vessels a central component of the circulatory system.
Baby’s heart at birth
Baby’s circulatory system will continue to slowly and steadily grow, so that by 40 weeks it’s ready for its debut outside the womb.
While the fetal circulatory system develops rapidly throughout pregnancy, it actually functions quite differently in utero than it does once baby is born. Before birth, baby’s lungs aren’t yet functioning, since baby doesn't breathe in utero. Until your baby is born and takes those first independent breaths, her developing circulatory system relies on the umbilical cord for a steady supply of oxygen- and nutrient-rich blood. Umbilical arteries and veins transport what baby needs from you to her, then carry unoxygenated blood and waste products back to you for removal.
A few other differences: The fetal heart has three shunts — or shortcuts — that direct blood away from the lungs (since they simply aren’t needed in utero) and the liver. Just like you, your baby has a pulmonary artery (bringing blood from the heart to the lungs) and aorta (bringing blood from the heart to the body). However these are connected by another blood vessel (the ductus arteriosus), which also serves to shunt blood away from the lungs in utero. Finally, your little one has a for-the-womb-only opening between the upper chambers of the heart (a patent foramen ovale), which again shunts blood away from the lungs.
Once baby is born, all of these fetal differences go away completely (or start to go away). When the umbilical cord is cut, baby’s lungs take in air, the fetal circulation system is switched off, the shunts begin to close. And all systems are go for baby.
How to keep baby’s heart healthy
A lot is developing and changing when your baby’s in the womb. While certain things are out of your control that can impact the development of your baby’s heart — like genetic abnormalities — there are steps you can take to help ensure your baby’s ticker is as healthy as possible:
Taking folic acid before and during pregnancy appears to help prevent congenital heart disease in babies.
If you are a smoker, quit ASAP: Researchers estimate that maternal smoking during the first trimester may account for up to 2 percent of all heart defects.
If you have type 2 diabetes or gestational diabetes, keep your blood sugar under control during pregnancy, since diabetes is associated with an increased risk of heart defects.
Don't take Accutane (for acne), which can also cause fetal heart defects.
Avoid alcohol and recreational drugs.
Even if you take every precaution and do everything your practitioner recommends, your baby may still be born with a congenital heart defect. This is not your fault. There are many factors — most out of your control — that can cause heart defects, and doctors are just starting to learn what some of them are. The good news is, with early detection, your baby can get the treatment she needs to increase the odds that she'll live a long, healthy life.
Let's start making that our starting date
< >
Since you found out you were pregnant, one of the first milestones you’ve likely eagerly been awaiting 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!
When your baby's heart begins developing.
Even though at 4 weeks pregnant that sweet, sweet heartbeat hasn’t yet arrived, a distinct blood vessel has formed inside your embryo, which will soon develop into your baby’s heart and circulatory (blood) system. In the early stages, the heart resembles a tube that twists and divides, eventually forming the heart and valves (which open and close to release blood from the heart to the body). In fact, by week 5, the heart tube begins to beat spontaneously, though you can't hear it. During those first few weeks, precursor blood vessels also begin to form in the embryo.
When you’ll hear baby’s heartbeat for the first time
By 6 weeks, your baby’s heart — now beating 110 times a minute — has four hollow chambers, each with an entrance and an exit to allow blood to flow in and out of each chamber. In just two more weeks, that number will rise to 150-170 beats a minute. That’s about twice as fast as yours!
With all of this growth, the chances are strong that you’ll be able to hear your baby’s heartbeat for the very first time around week 9 or week 10 of pregnancy. It will be about 170 beats per minutes by this time, a rate that will slow from here on out. Your doctor or midwife will place a handheld ultrasound device called a Doppler on your belly to amplify the telltale sound.
More on Fetal Development
Fetal Development: Baby’s Bones and Skeletal System
Fetal Development: Baby's Nervous System and Brain
Fetal Development: Baby’s Digestive System
Fetal Development: Baby's Hair, Skin & Nails
Can’t hear it yet? Don’t worry. It just means that your shy guy or gal is hiding in the corner of your uterus or has his or her back facing out, making it hard for the Doppler to find its target. In a few weeks (or at your next visit), the miraculous sound of your baby's heartbeat is certain to be audible for your listening pleasure. And your practitioner will check to make sure everything is okay, so feel free to ask any questions if you're concerned.
Ultrasound & congenital heart defects
Sometime between 6 weeks and 9 weeks of pregnancy, your practitioner (and/or a trained sonographer) will perform your first trimester ultrasound. It will not only confirm your pregnancy and estimated due date (along with how many babies you're carrying and the placement of the fetus) but also check that the heart is beating.
During your second trimester ultrasound, or 20-week anatomy scan, your doctor will check the structure of baby's heart and whether any problems (known as congenital heart defects) can be detected. About 36,000 babies (or 9 of every 1,000 infants) are born every year with a congenital heart defect, making this the most common type of major birth disorder. Although there is no medicine that can cure a heart defect in utero, and some defects can't be detected until after birth, a diagnosis during pregnancy helps doctors decide where to deliver your baby (usually in a large medical center, where pediatric cardiac care is available immediately after birth). Sometimes the issue needs to be handled with surgery right after birth, while other defects may need to be fixed at an older age or treated with medications. If your practitioner detects a fetal heart rhythm problem, she may prescribe medication to decrease the odds that your baby will be born early.
The good news is that the majority of congenital heart defects can be repaired and managed if detected early and treated promptly. Kids with congenital heart disease need to visit a cardiologist periodically throughout childhood and their adult lives.
You can hear baby’s heartbeat with a stethoscope!
Exciting circulatory developments continue at 12 weeks, when baby-to-be’s bone marrow begins busily producing blood cells. By 17 weeks, the fetal brain begins to regulate the heartbeat in preparation for supporting baby in the outside world. (Up until this point, the heart has been beating spontaneously.) In three more weeks, by around week 20, you can hear your baby’s heartbeat with a stethoscope.
If your doc needs a better listen (and a view), she may recommend that you get a fetal echocardiogram, a special ultrasound that evaluates the fetal heart, between 18 and 24 weeks. (If you have a family history of congenital heart defects, or if you personally have diabetes, phenylketonuria or autoimmune disease, make sure you get one.)
By now, baby's heart is beating at about 140 beats per minute. By the close of week 25, capillaries (the smallest blood vessels) are forming and filling with blood. Capillaries move oxygenated blood via the heart’s arteries to tissues throughout baby's body and then feed deoxygenated blood back to the lungs – making these teeny-tiny blood vessels a central component of the circulatory system.
Baby’s heart at birth
Baby’s circulatory system will continue to slowly and steadily grow, so that by 40 weeks it’s ready for its debut outside the womb.
While the fetal circulatory system develops rapidly throughout pregnancy, it actually functions quite differently in utero than it does once baby is born. Before birth, baby’s lungs aren’t yet functioning, since baby doesn't breathe in utero. Until your baby is born and takes those first independent breaths, her developing circulatory system relies on the umbilical cord for a steady supply of oxygen- and nutrient-rich blood. Umbilical arteries and veins transport what baby needs from you to her, then carry unoxygenated blood and waste products back to you for removal.
A few other differences: The fetal heart has three shunts — or shortcuts — that direct blood away from the lungs (since they simply aren’t needed in utero) and the liver. Just like you, your baby has a pulmonary artery (bringing blood from the heart to the lungs) and aorta (bringing blood from the heart to the body). However these are connected by another blood vessel (the ductus arteriosus), which also serves to shunt blood away from the lungs in utero. Finally, your little one has a for-the-womb-only opening between the upper chambers of the heart (a patent foramen ovale), which again shunts blood away from the lungs.
Once baby is born, all of these fetal differences go away completely (or start to go away). When the umbilical cord is cut, baby’s lungs take in air, the fetal circulation system is switched off, the shunts begin to close. And all systems are go for baby.
How to keep baby’s heart healthy
A lot is developing and changing when your baby’s in the womb. While certain things are out of your control that can impact the development of your baby’s heart — like genetic abnormalities — there are steps you can take to help ensure your baby’s ticker is as healthy as possible:
Taking folic acid before and during pregnancy appears to help prevent congenital heart disease in babies.
If you are a smoker, quit ASAP: Researchers estimate that maternal smoking during the first trimester may account for up to 2 percent of all heart defects.
If you have type 2 diabetes or gestational diabetes, keep your blood sugar under control during pregnancy, since diabetes is associated with an increased risk of heart defects.
Don't take Accutane (for acne), which can also cause fetal heart defects.
Avoid alcohol and recreational drugs.
Even if you take every precaution and do everything your practitioner recommends, your baby may still be born with a congenital heart defect. This is not your fault. There are many factors — most out of your control — that can cause heart defects, and doctors are just starting to learn what some of them are. The good news is, with early detection, your baby can get the treatment she needs to increase the odds that she'll live a long, healthy life.
