When Can You Hear a Heartbeat on Ultrasound?

A fetal heartbeat may first be detected on a transvaginal ultrasound as early as 5½ to 6 weeks after conception (timing varies by equipment and individual factors; costs and availability may differ by year and location).

You’ve just seen a positive pregnancy test, and now the waiting begins. The next big milestone — that first flicker of cardiac activity on a screen — feels both urgent and mysterious. Friends share stories of hearing a heartbeat at 6 weeks, while others say they had to wait until 8 or 9 weeks, which can stir up unnecessary worry.

The honest answer is that detection timing depends on several factors, including the type of ultrasound used and the accuracy of your gestational age. Here’s what the research says about when a fetal heartbeat can typically be seen and what to expect at each stage.

When a Heartbeat First Becomes Visible

The earliest opportunity to see cardiac activity is around 5½ to 6 weeks of pregnancy. At this point, the embryo’s heart tube has just started to beat, and its rate ranges from roughly 90 to 110 beats per minute.

For the best chance of seeing it that early, a transvaginal ultrasound is needed. An abdominal ultrasound usually can’t pick up the heartbeat until around 8 weeks, because the sound waves have to travel through more tissue and the embryo is still very small.

By 6½ to 7 weeks, detection becomes much more reliable, and doctors can begin to assess pregnancy viability. If you’re only 6 weeks along and the heartbeat isn’t visible, that can be perfectly normal — the timing of implantation and growth varies.

Why Early Detection Varies So Much

It’s easy to assume that if a heartbeat isn’t seen at 6 weeks, something is wrong. In reality, the most common reason is simply that the pregnancy is slightly earlier than calculated. Ovulation and implantation can shift by several days, making a 6-week scan really closer to 5 weeks.

Here are the main factors that influence when a heartbeat can be detected:

• Accuracy of gestational age: A miscalculation of one to two weeks is common, especially if cycles are irregular. A scan at what you think is 7 weeks may actually be only 5½ weeks.
• Type of ultrasound used: Transvaginal probes provide much clearer images early on than abdominal ones, which are better suited for later weeks.
• Position of the uterus: A tilted or retroverted uterus can sometimes make it harder to see the embryo, delaying detection by a few days.
• Quality of the equipment: Not all ultrasound machines have the same resolution, and provider experience also plays a role.
• Embryo growth rate: Some embryos develop a bit more slowly in the very early weeks, without any negative outcome.

Most providers will not rush to any conclusion based on a single early scan. They typically consider the entire picture — including hCG levels and symptoms — before deciding on next steps.

What to Expect on Your First Ultrasound

Your first pregnancy ultrasound is usually scheduled between 8 and 12 weeks. By that point, a transvaginal or abdominal scan should clearly show a heartbeat. If you need an earlier scan — for instance, if you have spotting or a history of loss — your doctor may order one around 6 to 7 weeks.

During the scan, the technician will measure the crown-rump length and look for cardiac activity. If a heartbeat is seen, it’s an assuring sign. The presence of earliest detection of fetal heartbeat is widely considered a positive indicator of early pregnancy health, though no single measurement guarantees everything will go smoothly.

If no heartbeat is detected at 6 or 7 weeks, your provider may suggest a repeat scan in 7 to 14 days. In many cases, a heartbeat appears on the second scan that wasn’t visible the first time.

Keep in mind that even the most advanced ultrasound has limits. A small embryo or early gestational age can easily hide the heartbeat, and that’s not a cause for alarm on its own.

What Happens If a Heartbeat Isn’t Detected

Not hearing or seeing a heartbeat at an early scan can be nerve-racking, but it doesn’t automatically mean the pregnancy is not progressing. Your provider will follow a structured approach to get clearer information.

1. Confirm gestational age: They will compare your last menstrual period, hCG levels, and the ultrasound measurements to see if the dates add up.
2. Check hCG trends: A rising hCG level that doubles every 48 to 72 hours suggests the pregnancy is growing, even if the heartbeat isn’t visible yet.
3. Schedule a repeat scan: Waiting 1 to 2 weeks for a follow-up ultrasound is standard practice. By then, the embryo should be large enough to assess cardiac activity.
4. Consider alternative explanations: A tilted uterus, a late ovulation, or even a suboptimal scanning angle can delay detection without any underlying problem.
5. Provide supportive care: If there’s still no heartbeat after the follow-up and hCG is falling, your doctor will discuss options for confirming a nonviable pregnancy and next steps.

The key takeaway: a single early scan without a heartbeat is rarely conclusive. Most guidelines recommend reserving judgment until at least 7 weeks, and often later.

Understanding Fetal Heart Rate Patterns

Once a heartbeat is detected, its rate changes predictably across the first trimester. The fetal heart starts beating around 90 bpm and climbs rapidly. According to Johns Hopkins Medicine, the average fetal heart rate range is 110 to 160 bpm later in pregnancy, but early rates differ significantly.

At 6 to 7 weeks, 90–110 bpm is normal. By 9 weeks, the rate peaks at about 170 bpm, then gradually declines after 13 weeks to around 130 bpm at term. This pattern is well-documented in peer-reviewed studies and reflects the developing autonomic nervous system.

It’s important to remember that a single heart rate reading isn’t diagnostic. The rate can vary by 5 to 25 bpm depending on the baby’s movement, uterine conditions, and even the time of day. Your provider looks at trends over time, not one number.

These ranges are general guidelines, not strict rules. Some babies naturally run a bit faster or slower, and that’s usually fine.

The Bottom Line

You can typically expect to see a fetal heartbeat on a transvaginal ultrasound between 6½ and 7 weeks, with the earliest possible detection at 5½ weeks. An abdominal ultrasound may require waiting until 8 weeks. If the heartbeat isn’t visible at an early scan, a repeat scan in one to two weeks often resolves the uncertainty.

Your obstetrician or midwife will track your hCG levels and ultrasound findings together to give you the most complete picture. If your scan dates seem off or detection takes a little longer, ask your provider to walk you through what they see and what the numbers mean for your specific situation.