One of the milestones of fetal development is when the heart begins to beat. In most cases, an ultrasound can detect the beating of cardiac tissue around weeks five to six, and the heart will form within the next few weeks.
Below, we look into the timeline of a fetus developing a heartbeat and describe how and when a healthcare professional can detect it.
Before about week 8 of pregnancy, a doctor may refer to the fetus as an embryo.
Cardiac tissue starts to pulse at around 5–6 weeks of pregnancy, registering as a heartbeat on the ultrasound, though the heart has not developed yet. Also, it may be
The heart of a fetus is fully developed by the
|Week of pregnancy||Level of heart development|
|week 5||The developing heart is made up of two tubes that have fused in the middle, creating a trunk with four tubes branching off. |
Cardiac tissue begins to contract, and it may be possible to detect it using vaginal ultrasound.
|week 6||The heart of the embryo has changed dramatically — the basic heart tube has looped, forming an “S” shape.|
|week 7||The pumping chambers, or ventricles, and receiving chambers, or atria, of the heart begin to separate and develop.|
|week 8||The valves between the atria and ventricles of the heart form.|
|weeks 9 and 10||The aorta and pulmonary vein form. By week 10, the fetal heart has developed fully.|
Cardiac contractions will be visible by ultrasound well before they are audible with typical Doppler handheld devices in offices.
The heart rate of a fetus changes as it develops. In general, the rate is 110–160 beats per minute.
A pregnant person may undergo a scan to detect the fetal heartbeat at different stages of pregnancy. A doctor may recommend a scan as early as 6 weeks if the person has had spotting, bleeding, or problems with a previous pregnancy.
A healthcare professional may perform an ultrasound in the first trimester to:
- confirm the pregnancy and check the age of the fetus
- check for a suspected ectopic pregnancy
- evaluate bleeding or pain
- check the number of fetuses
- check the heartbeat of the fetus
- look for any fetal or uterine abnormalities
- look for and remove an intrauterine device
A healthcare professional can detect the heartbeat of a fetus in numerous ways, including:
A transvaginal scan is internal. The doctor inserts a device into the vagina to monitor the development of the embryo. However, until roughly the seventh week of pregnancy, it can be difficult to detect the heartbeat of the embryo.
A transvaginal scan can also be useful after 11 weeks if an abdominal scan does not provide a clear picture of the fetus.
During the second and third trimesters, a transabdominal scan can help assess the pregnancy.
To perform it, a healthcare professional spreads lubricating gel on the pregnant person’s lower abdomen. They then move a handheld ultrasound scanner device across the abdomen to find the uterus and fetus.
By the second trimester, the heart of the fetus is fully formed, and healthcare professionals should see the
Healthcare professionals use transabdominal scans in the second or third trimesters to:
- determine the age and growth of the fetus
- check for multiple fetuses
- check the condition of the fetus
- evaluate the cervix
- evaluate the uterus
- check on any previously detected issues
- examine the amniotic fluid and placenta
- evaluate any bleeding or pain
- check on any suspicious masses
- check for any abnormal biochemical markers
- check on or for fetal anomalies
- look for signs of premature labor
- confirm a suspected ectopic pregnancy
- assess pregnancy loss
Fetal heart rate monitoring
A healthcare professional uses a fetal heart rate monitor during labor to check for any changes. There are two ways to monitor the fetal heart rate at this time:
- Auscultation: This involves holding a special stethoscope or a Doppler transducer against the pregnant person’s abdomen and listening for the fetal heartbeat. The doctor may do this at specific times during labor.
- Electronic fetal monitoring: This involves using specialized internal or external equipment to measure the heart rate in response to contractions. It provides an ongoing reading, which the doctor can check at set times.
“Doptone” is a brand name for a handheld Doppler stethoscope. These devices are available online but are not approved for over-the-counter sale.
A healthcare professional may not be able to find the fetal heartbeat during a scan due to:
- the scan taking place too early in the pregnancy
- the pregnant person having a
- an ectopic pregnancy
The doctor will expect to hear a heartbeat once the fetus is 7 millimeters or more in length. If they cannot detect a heartbeat, the doctor may ask the person to come back for another scan in a week or so.
If the doctor or midwife is concerned, they may ask for a scan by an ultrasound expert.
The heart of an embryo starts beating at about week 5 of pregnancy. It may be possible to detect the heartbeat at this point using vaginal ultrasound.
Throughout the pregnancy and delivery, healthcare professionals monitor the heartbeat of the fetus.
If a pregnant person has concerns about the fetal heartbeat, they should contact a doctor or midwife.