Being told that your baby’s heartbeat cannot be seen during an early pregnancy scan can be extremely worrying. For many women, the immediate concern is whether the pregnancy has stopped developing or whether it is simply too early to see a heartbeat.
The absence of a visible heartbeat does not always mean that a miscarriage has occurred.
During the earliest weeks of pregnancy, even a difference of a few days can significantly affect what is visible on ultrasound. The interpretation depends on how far the pregnancy has developed, the size of the embryo and the type of ultrasound examination performed.
Understanding these factors can help explain why a repeat scan may sometimes be necessary before a definite conclusion can be reached.
Key points
- The baby’s heart begins developing very early in pregnancy, and the first movements of the developing heart may become visible on ultrasound at approximately six weeks.
- By seven to eight weeks, an embryo and its heartbeat would normally be visible on ultrasound in a developing pregnancy.
- One of the most important measurements during an early pregnancy scan is the crown–rump length (CRL).
- Sometimes an ultrasound scan demonstrates a gestational sac within the uterus, but an embryo cannot yet be seen.
When should a baby’s heartbeat first be visible?
The baby’s heart begins developing very early in pregnancy, and the first movements of the developing heart may become visible on ultrasound at approximately six weeks. At this stage, the embryo is extremely small, often measuring only a few millimetres.
A transvaginal ultrasound can sometimes demonstrate heart activity at around six weeks, although it may not yet be visible in every normally developing pregnancy. By approximately seven weeks, heart activity is usually clearly visible when the pregnancy is developing normally and the dates are accurate.
However, pregnancy dates alone cannot determine whether a heartbeat should be visible. The size of the embryo and the quality of the ultrasound images are particularly important.
Read more: When Can You See a Baby’s Heartbeat on an Early Pregnancy Scan?
Why might there be no heartbeat at six weeks?
There are several reasons why a heartbeat may not be visible during an ultrasound examination at six weeks.
The pregnancy may be earlier than expected
Pregnancy dates are usually calculated from the first day of the last menstrual period. Most pregnancy apps use this calculation and commonly assume a 28-day menstrual cycle, with ovulation occurring around day 14. However, ovulation does not always occur on day 14. Even women with regular menstrual cycles may ovulate several days earlier or later than expected.
If ovulation occurred later, the embryo may be younger and smaller than anticipated. A pregnancy thought to be six weeks may therefore be closer to five weeks and a few days, when heart activity may not yet be visible.
The embryo may still be very small
At the earliest stages of development, the embryo may measure only one or two millimetres. Heart activity can be difficult to identify reliably when the embryo is extremely small, even with high-quality ultrasound equipment.
The type of ultrasound examination may affect visibility
An abdominal ultrasound may not provide sufficiently detailed images during the earliest weeks of pregnancy. A transvaginal ultrasound places the probe closer to the uterus and can often demonstrate structures that are not yet clearly visible on an abdominal scan. Factors such as the position of the uterus, maternal body habitus and the quality of the ultrasound images may also affect visibility.
The pregnancy may not be developing normally
In some circumstances, the absence of heart activity may indicate that the pregnancy has stopped developing. However, this conclusion should only be reached when established ultrasound criteria have been satisfied.
Read more: What Can You See on a Pregnancy Scan at 5, 6, 7 and 8 Weeks?
What if there is no heartbeat at seven or eight weeks?
By seven to eight weeks, an embryo and its heartbeat would normally be visible on ultrasound in a developing pregnancy. If no heartbeat is identified at this stage, the finding requires careful assessment. However, the number of weeks calculated from the last menstrual period is not sufficient to diagnose miscarriage.
For example, a woman who believes she is eight weeks pregnant may have ovulated later than expected, particularly if her menstrual cycles are irregular. The clinician should therefore assess the size of the embryo rather than relying on pregnancy dates alone.
If the embryo is very small, a repeat ultrasound may be necessary to determine whether the pregnancy is continuing to develop. If the embryo has reached a size at which heart activity would normally be expected, the absence of a heartbeat becomes more concerning.
How does the size of the embryo help determine whether a miscarriage has occurred?
One of the most important measurements during an early pregnancy scan is the crown–rump length (CRL). This is the measurement of the embryo from the top of its head to the bottom of its body. The CRL helps the clinician assess how far the pregnancy has developed and interpret the absence of visible heart activity.
Embryo less than 7 mm, no heartbeat visible: the pregnancy may still be too early for a definite diagnosis. Another ultrasound scan should be performed after at least seven days.
Embryo 7 mm or more, no heartbeat visible: the findings are strongly suggestive of miscarriage. However, NICE recommends obtaining a second opinion and/or repeating the ultrasound after at least seven days before confirming the diagnosis.
What if the gestational sac is visible but there is no embryo or heartbeat?
Sometimes an ultrasound scan demonstrates a gestational sac within the uterus, but an embryo cannot yet be seen. This is a different situation from seeing an embryo without a heartbeat. During the earliest weeks, the gestational sac usually becomes visible before the embryo.
If the pregnancy is very early, it may therefore be normal to see a gestational sac without an identifiable embryo or heart activity. The clinician may measure the gestational sac to assess whether its size is consistent with a very early pregnancy.
If the findings remain uncertain, another ultrasound scan will be recommended after an appropriate interval.
For a detailed explanation of the ultrasound measurements used to diagnose pregnancy loss, read our guide: Miscarriage and Early Pregnancy Loss: How Is It Diagnosed?
Why do I need to wait before having another scan?
Waiting for a repeat ultrasound can be difficult, particularly when you are worried about the outcome of your pregnancy. However, a repeat examination performed too soon may not provide any additional information.
During early pregnancy, the embryo grows rapidly. Allowing sufficient time between scans makes it easier to determine whether normal growth has occurred and whether heart activity has become visible. The recommendation is to wait at least seven days before repeating a transvaginal ultrasound when the findings are uncertain. When the initial assessment has been performed using an abdominal ultrasound and the findings are inconclusive, a longer interval of at least 14 days may be necessary.
Waiting for an appropriately timed repeat scan does not harm the pregnancy or increase the risk of miscarriage.
Can pregnancy hormone levels tell whether the heartbeat will appear?
The pregnancy hormone, human chorionic gonadotrophin (β-hCG), is produced during pregnancy and can be measured in the blood. In the earliest weeks, β-hCG levels generally rise as the pregnancy develops. However, the rate of increase varies between women, and a single blood test cannot reliably establish whether a pregnancy is developing normally.
When the pregnancy is too early to assess clearly on ultrasound, or its location has not yet been confirmed, blood tests taken approximately 48 hours apart may provide additional information. However, β-hCG levels cannot confirm whether a baby’s heartbeat is present or predict with certainty whether it will become visible.
Once an embryo is visible, ultrasound assessment of its size and heart activity is generally more informative than hormone levels.
Read more: Understanding hCG Levels in Early Pregnancy
Does having pregnancy symptoms mean the baby is still developing?
Pregnancy symptoms such as nausea, breast tenderness and tiredness are caused partly by hormonal changes. These symptoms may continue even when a pregnancy has stopped developing because pregnancy hormone levels do not fall immediately.
Equally, some women experience very few pregnancy symptoms despite having a normally developing pregnancy. A reduction or disappearance of pregnancy symptoms does not, by itself, establish that a miscarriage has occurred.
Pregnancy symptoms cannot reliably confirm whether the baby has a heartbeat. Ultrasound remains the most appropriate investigation when there is uncertainty about pregnancy development.
What happens if a heartbeat is seen on the repeat scan?
If the repeat ultrasound demonstrates appropriate embryo growth and visible heart activity, this is a reassuring finding. It may indicate that the pregnancy was simply earlier than expected at the time of the first examination.
Your clinician can use the embryo’s measurements to assess the gestational age and advise whether any further follow-up is necessary. Research shows that the risk of miscarriage generally decreases as pregnancy progresses after a heartbeat has been confirmed.
For more information, read our guide: Miscarriage in Early Pregnancy: How Likely Is It and Why Does It Happen?
What happens if there is still no heartbeat?
If a repeat ultrasound demonstrates that the embryo has not developed as expected and heart activity remains absent, the findings may confirm an early pregnancy loss.
The diagnosis should be based on established ultrasound criteria and the findings from the examinations, rather than pregnancy dates alone. Once miscarriage has been confirmed, your clinician should explain the results sensitively and discuss the available management options.
These may include allowing the miscarriage to occur naturally, medication or surgical treatment, depending on the circumstances and your preferences. A diagnosis should not be made prematurely when there remains uncertainty about the ultrasound findings.
When should I seek urgent medical attention?
If you experience vaginal bleeding, abdominal pain or other concerning symptoms while awaiting a repeat ultrasound, contact your GP, midwife or local NHS Early Pregnancy Assessment Service for advice.
Seek urgent medical assessment if you develop heavy bleeding, severe or worsening abdominal pain, significant one-sided pelvic pain, shoulder-tip pain, dizziness or fainting.
These symptoms may occasionally indicate significant bleeding or an ectopic pregnancy.
If you experience collapse, severe pain or heavy bleeding with faintness, call 999 or attend an Emergency Department immediately.
Understanding an early scan without a visible heartbeat
Not seeing a heartbeat on an early pregnancy scan can be distressing, but it does not always mean that the pregnancy has ended.
At six weeks, the pregnancy may simply be too early for heart activity to be demonstrated. At seven or eight weeks, the finding becomes more concerning, but the interpretation must still depend on the embryo’s measurements and the quality of the ultrasound examination.
The most important principle is that miscarriage should never be diagnosed prematurely.
Where uncertainty remains, an appropriately timed repeat ultrasound provides the safest and most reliable way to establish whether the pregnancy is developing normally.
Related pregnancy guides
Frequently asked questions
When should a baby’s heartbeat first be visible?
The baby’s heart begins developing very early in pregnancy, and the first movements of the developing heart may become visible on ultrasound at approximately six weeks. At this stage, the embryo is extremely small, often measuring only a few millimetres.
Why might there be no heartbeat at six weeks?
There are several reasons why a heartbeat may not be visible during an ultrasound examination at six weeks. Pregnancy dates are usually calculated from the first day of the last menstrual period.
What if there is no heartbeat at seven or eight weeks?
By seven to eight weeks, an embryo and its heartbeat would normally be visible on ultrasound in a developing pregnancy. For example, a woman who believes she is eight weeks pregnant may have ovulated later than expected, particularly if her menstrual cycles are irregular.
How does the size of the embryo help determine whether a miscarriage has occurred?
One of the most important measurements during an early pregnancy scan is the crown–rump length (CRL). This is the measurement of the embryo from the top of its head to the bottom of its body.
What if the gestational sac is visible but there is no embryo or heartbeat?
Sometimes an ultrasound scan demonstrates a gestational sac within the uterus, but an embryo cannot yet be seen. This is a different situation from seeing an embryo without a heartbeat.
Why do I need to wait before having another scan?
Waiting for a repeat ultrasound can be difficult, particularly when you are worried about the outcome of your pregnancy. However, a repeat examination performed too soon may not provide any additional information.
Early pregnancy care at The Pregnancy Clinic
At The Pregnancy Clinic, we provide consultant-led early pregnancy ultrasound examinations, including assessment when a heartbeat has not yet been identified or pregnancy development is uncertain.
Our approach is to assess the embryo’s measurements carefully, explain the ultrasound findings and arrange appropriate follow-up when a repeat examination is necessary.
We understand that waiting for another scan can be particularly difficult. Our aim is to provide clear, sensitive and evidence-based guidance while ensuring that no premature conclusions are reached.
Book an early pregnancy consultation → 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.