A fetus goes through many stages of development. One of the milestones is when the heart begins to beat.
Below, we look into the timeline of a fetus developing a heartbeat and describe how and when a healthcare provider can detect it.
Before about week 8 of pregnancy, a doctor may refer to the fetus as an embryo.
The heart of an embryo starts to beat from around 5–6 weeks of pregnancy. Also, it may be possible to see the first visible sign of the embryo, known as the fetal pole, at this stage.
The heart of a fetus is fully developed by the 10th week of pregnancy. Learn more about the development of the heart from weeks 5–10 below:
|Week of pregnancy||Level of heart development|
|5th week||The developing heart is made up of two tubes that have fused in the middle, creating a trunk with four tubes branching off. |
The heart begins to beat, and it may be possible to detect it using vaginal ultrasound.
|6th week||The heart of the embryo has changed dramatically — the basic heart tube has looped, forming an S-shape and creating an area for the ventricles.|
|7th week||The ventricles and atria of the heart begin to separate and develop.|
|8th week||The valves between the atria and ventricles of the heart form.|
|9th and 10th weeks||The aorta and pulmonary vein form. By the 10th week, the fetal heart will have developed fully.|
It may be possible to hear the heartbeat of an embryo from the fifth week of pregnancy. However, a scan at this stage is unlikely to show anything related to the embryo’s heartbeat.
The heart rate of a fetus changes as it develops. In general, the rate is 110–160 beats per minute.
A woman may have a scan to detect the fetal heartbeat at different stages of pregnancy. A doctor may recommend a scan as early as 7 weeks if the woman has had spotting, bleeding, or problems with a previous pregnancy.
A healthcare provider 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 for the number of fetuses
- check the heartbeat of the fetus
- look for any fetal or uterine abnormalities
- check for suspected abnormal cells or masses
- look for and remove an intrauterine device, or IUD
A doctor 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 7th week of pregnancy, the heartbeat of the embryo can be difficult to detect.
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, the healthcare provider spreads lubricating gel onto the woman’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 the doctor should see the heart beating on the scan.
A doctor uses 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 provider 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 woman’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.
A doptone is an over-the-counter fetal heartbeat monitor. The Food and Drug Administration (FDA) warn that only medical professionals should use these devices — an untrained person may expose the fetus to unsafe energy levels.
A doctor may not be able to find the fetal heartbeat during a scan due to:
- the scan taking place too early in the pregnancy
- the woman having a larger abdomen
- 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 woman to come back for another scan in a week or so.
If the doctor is concerned, they may schedule a fetal echocardiogram. This involves placing a device that uses ultrasonic waves to detect the fetal heartbeat against the woman’s abdomen.
The heart of an embryo starts beating at about week 5 of pregnancy. It may be possible to detect, at this point, using vaginal ultrasound.
Throughout the pregnancy and delivery, healthcare providers monitor the heartbeat of the fetus.
Anyone who has concerns about the fetal heartbeat should contact a doctor.