Seeing your baby’s heartbeat for the first time is often one of the most reassuring moments of an early pregnancy scan.
One of the questions women commonly ask is how early a heartbeat can be detected and whether it should be visible at five, six or seven weeks of pregnancy.
Embryonic heart activity may first become visible on ultrasound at around six weeks of pregnancy. By seven weeks, it can usually be identified in a normally developing pregnancy.
However, the exact timing varies, and not seeing heart activity during a very early scan does not necessarily mean that something is wrong.
Key points
- The developing heart begins to show rhythmic activity during the earliest stages of embryonic development, before the heart has acquired its mature structure.
- One of the most common reasons why a baby’s heartbeat may not be visible at six weeks is that the pregnancy is earlier than expected.
- During an early pregnancy scan, the clinician identifies the gestational sac, yolk sac and embryo.
- Identifying embryonic heart activity is an encouraging finding.
When does a baby’s heartbeat first become visible?
The developing heart begins to show rhythmic activity during the earliest stages of embryonic development, before the heart has acquired its mature structure.
With modern ultrasound equipment, this activity may be identified from approximately six weeks of pregnancy, particularly when a transvaginal scan is performed.
At this stage, the embryo is extremely small, and heart activity appears as a tiny, rhythmic flicker within it.
At five weeks, the embryo may not yet be visible, so it is generally too early to expect heart activity to be demonstrated.
By six weeks, an embryo and its heart activity may be seen, although this depends on the exact stage of pregnancy development.
By seven weeks, embryonic heart activity can usually be demonstrated, making this a particularly useful time for an early pregnancy scan.
Read more: What Can You See on a Pregnancy Scan at 5, 6, 7 and 8 Weeks?
Why might a heartbeat not be visible at six weeks?
One of the most common reasons why a baby’s heartbeat may not be visible at six weeks is that the pregnancy is earlier than expected.
Pregnancy is usually dated from the first day of your last menstrual period (LMP). Most pregnancy calculators and mobile pregnancy apps use this same method to estimate how many weeks pregnant you are.
These calculations generally assume a menstrual cycle of 28 days, with ovulation occurring around day 14.
However, this does not necessarily reflect when ovulation actually occurred.
Even in women with regular menstrual cycles, ovulation may occur earlier or later than expected, for example between approximately days 12 and 18. This means that conception, and therefore the actual developmental age of the embryo, may differ by several days from the estimate provided by a pregnancy app.
The variation can be even greater in women with shorter, longer or irregular menstrual cycles.
For example, a pregnancy calculated as six weeks from the last menstrual period may actually be only five weeks and a few days in terms of its ultrasound development.
This difference is particularly important in early pregnancy because even three or four days can make a significant difference to whether an embryo and its heart activity can be identified.
The type of ultrasound examination also matters. At five or six weeks, transvaginal ultrasound generally provides clearer images of a very small embryo than an abdominal scan.
For these reasons, the absence of visible heart activity at six weeks does not automatically indicate a miscarriage.
The findings should always be interpreted alongside the embryo’s measurements and the other ultrasound appearances, rather than menstrual dates or pregnancy app calculations alone.
How is the baby’s heartbeat assessed during an early pregnancy scan?
During an early pregnancy scan, the clinician identifies the gestational sac, yolk sac and embryo.
Once the embryo is visible, the clinician looks for rhythmic movement within the developing heart.
This is usually assessed using real-time ultrasound imaging, which allows the movement to be observed directly.
When appropriate, the embryonic heart rate may also be measured using ultrasound techniques such as M-mode.
In the earliest weeks, the primary purpose is to establish whether heart activity is present and to assess the embryo’s development.
It is not routinely necessary to listen to the heartbeat using Doppler ultrasound during a very early pregnancy scan. Ultrasound exposure should be kept to the minimum necessary to obtain the required clinical information.
Does seeing a heartbeat mean the pregnancy is progressing normally?
Identifying embryonic heart activity is an encouraging finding.
It confirms that the embryo has developed to a stage at which cardiac activity can be demonstrated and provides important information about pregnancy viability at the time of the examination.
The risk of subsequent miscarriage generally decreases as pregnancy progresses, particularly when heart activity is seen and embryonic growth is appropriate for gestational age.
However, seeing a heartbeat does not guarantee that the pregnancy will continue without complications.
The overall assessment also depends on factors such as the embryo’s crown–rump length, heart rate when measured, pregnancy dating, maternal age, clinical history and any symptoms.
An early pregnancy scan also cannot exclude all fetal abnormalities or complications that may develop later.
Read more: Miscarriage in Early Pregnancy: How Likely Is It and Why Does It Happen?
What if a heartbeat cannot be seen?
Sometimes an ultrasound examination identifies an embryo, but heart activity cannot be demonstrated.
The significance of this finding depends particularly on the size of the embryo, measured as the crown–rump length (CRL).
Embryo less than 7 mm, no heart activity (transvaginal scan): the pregnancy may simply be too early for a definitive assessment. A repeat scan after at least seven days is recommended before diagnosing a miscarriage.
Embryo 7 mm or more, no heart activity (transvaginal scan): this is strongly suggestive of miscarriage. However, because an incorrect diagnosis could have serious consequences, national guidance recommends obtaining a second opinion and/or repeating the ultrasound after at least seven days before confirming the diagnosis.
Abdominal scan, no heart activity: different precautions apply, and a repeat scan after at least 14 days is recommended.
It is therefore important that the diagnosis is based on appropriate ultrasound measurements and established clinical criteria, rather than the number of weeks calculated from the last menstrual period alone.
For a more detailed explanation, read our guide: No Heartbeat on an Early Pregnancy Scan: Is It Too Early?
Is an abdominal scan sufficient to see the heartbeat?
At or after seven weeks, an abdominal ultrasound scan performed through the tummy can usually demonstrate the embryo and its heart activity.
Occasionally, the views may be less clear because of a retroverted uterus, uterine fibroids, an incompletely filled bladder or a pregnancy that is earlier than expected.
In these circumstances, a transvaginal ultrasound scan may be offered to obtain clearer images.
Transvaginal ultrasound is safe in early pregnancy and does not increase the risk of miscarriage.
Your clinician should explain the examination and discuss whether additional imaging would be helpful.
When should I seek medical advice?
If you have vaginal bleeding or abdominal pain in early pregnancy, you should seek appropriate clinical advice rather than relying solely on a previously reassuring scan.
Seek urgent assessment for heavy bleeding, severe or worsening abdominal pain, significant one-sided pelvic pain, shoulder-tip pain, dizziness, fainting or collapse.
For severe symptoms, attend an Emergency Department or call 999. For other urgent concerns, contact your local NHS Early Pregnancy Assessment Service or NHS 111.
Read more: Bleeding in Early Pregnancy: What Does It Mean?
Understanding your baby’s first heartbeat
Embryonic heart activity may first be visible from around six weeks, and by seven weeks it can usually be demonstrated on ultrasound.
The timing varies between pregnancies, particularly when ovulation has occurred later than expected.
Seeing heart activity is an encouraging milestone, but the finding should always be interpreted alongside the embryo’s measurements, gestational age and clinical circumstances.
A carefully performed early pregnancy scan can provide valuable reassurance while ensuring that uncertain findings are assessed appropriately.
Related pregnancy guides
Frequently asked questions
When does a baby’s heartbeat first become visible?
The developing heart begins to show rhythmic activity during the earliest stages of embryonic development, before the heart has acquired its mature structure.
Why might a heartbeat not be visible at six weeks?
One of the most common reasons why a baby’s heartbeat may not be visible at six weeks is that the pregnancy is earlier than expected.
How is the baby’s heartbeat assessed during an early pregnancy scan?
During an early pregnancy scan, the clinician identifies the gestational sac, yolk sac and embryo.
Does seeing a heartbeat mean the pregnancy is progressing normally?
Identifying embryonic heart activity is an encouraging finding. It confirms that the embryo has developed to a stage at which cardiac activity can be demonstrated and provides important information about pregnancy viability at the time of the examination.
What if a heartbeat cannot be seen?
Sometimes an ultrasound examination identifies an embryo, but heart activity cannot be demonstrated.
Is an abdominal scan sufficient to see the heartbeat?
At or after seven weeks, an abdominal ultrasound scan performed through the tummy can usually demonstrate the embryo and its heart activity.
Early pregnancy care at The Pregnancy Clinic
At The Pregnancy Clinic, early pregnancy ultrasound examinations are provided as part of a consultant-led pregnancy and fetal medicine service.
We assess embryonic heart activity, growth and pregnancy development alongside your individual history and circumstances, providing clear explanations and appropriate advice about further assessment when needed.
Book an early pregnancy scan →The Pregnancy Clinic is not an emergency service. If you experience severe pain, heavy bleeding, fainting or other acute symptoms, please seek urgent NHS assessment.