Your baby’s heart rate changes a great deal over the course of pregnancy. In the first few weeks it speeds up quickly, peaks at around 9 weeks and then slowly settles. For most of the second and third trimesters, a fetal heart rate of 110–160 beats per minute (bpm) is considered normal. Your own heart rate changes too: the maternal heart rate usually rises a little as your body adapts to pregnancy.
This guide explains when a heartbeat can first be seen on a scan, what is typical week by week, what a slow or not-yet-visible heartbeat at 6–8 weeks can mean, and why a repeat scan is often the right next step.
In short: a heartbeat is often visible on an internal (transvaginal) scan from around 6 weeks, at roughly 100–130 bpm. It climbs to about 160–185 bpm by 8–10 weeks, then gradually slows to the 110–160 bpm range seen for the rest of pregnancy.
When can you first see a baby’s heartbeat on a scan?
At around 6 weeks of pregnancy (counted from the first day of your last period), the embryo is only about 6 mm long. The NHS notes that at this stage the heartbeat can sometimes be picked up by a vaginal ultrasound scan. On screen it looks like a tiny, rapid flicker in the middle of the embryo, and the sonographer measures its rate from the image.
“Sometimes” is the important word. If you ovulated later than average, or aren’t sure of the date of your last period, you may be less far along than you think. A healthy pregnancy can then look “too early” at the first scan. For that reason, many people choose to wait until 7–8 weeks for a first private scan, when the heartbeat and the embryo are much easier to see.
Our viability scan (6–9 weeks) is designed for exactly this question: it looks for the heartbeat, confirms the pregnancy is in the womb, checks how many babies there are and dates the pregnancy. You can book a viability scan (£140) online at either of our London clinics.
Baby’s heart rate by week
The table below shows typical embryonic and fetal heart rates. The first-trimester figures come from a 2020 study in BMC Pregnancy and Childbirth that measured more than 30,000 IVF pregnancies. Because IVF pregnancies have precisely known dates, they make a useful reference. The “typical range” covers the middle 90 per cent of healthy pregnancies (the 5th to 95th centiles).
| Stage of pregnancy | Typical range | Average (median) |
|---|---|---|
| 6 weeks | 103–128 bpm | 117 bpm |
| 7 weeks | 124–165 bpm | 146 bpm |
| 8 weeks | 158–186 bpm | 174 bpm |
| 9 weeks | 162–188 bpm | 176 bpm (the peak) |
| 10 weeks | 160–186 bpm | 174 bpm |
| 10–14 weeks | Gradually slowing | From about 170 bpm to about 155 bpm |
| Second and third trimesters | 110–160 bpm | Varies with activity and sleep |
The heart rate climbs steeply between 6 and 8 weeks. It reaches its highest point at around 9 weeks and then begins a slow decline. A large study of pregnancies scanned at 10–14 weeks found that the average heart rate fell from about 170 bpm to about 155 bpm over that period. Later in pregnancy, 110–160 bpm is the range generally regarded as normal. It is also the baseline range NICE uses when monitoring a baby’s heart rate in labour.
A few points help when reading these numbers:
- A range, not a target. A single reading a little above or below the typical range is not in itself a diagnosis. Your clinician interprets it alongside the baby’s size, your dates and the rest of the scan.
- Days matter early on. At 6–7 weeks the rate rises so quickly that a few days’ difference in dating can change what counts as “expected”.
- Heart rates vary moment to moment. Later in pregnancy, the rate naturally speeds up when your baby moves and slows during rest.
What if the heartbeat is slow, or can’t be seen yet, at 6–8 weeks?
This is one of the most worrying moments in early pregnancy, so it helps to know how clinicians approach it. Very often the explanation is simply that the pregnancy is earlier than expected.
No heartbeat seen yet
NICE guidance on early pregnancy (NG126) sets out cautious rules to minimise the chance that a pregnancy that is still developing is mistakenly declared a miscarriage. On a transvaginal scan:
- If the embryo’s crown–rump length (CRL, the measurement from the top of the head to the bottom) is less than 7 mm and no heartbeat is visible, a second scan should be done at least 7 days later before any diagnosis is made.
- If the CRL is 7 mm or more with no visible heartbeat, NICE advises seeking a second opinion and/or repeating the scan at least 7 days later.
- If no embryo is visible yet, the size of the pregnancy sac guides the next step in a similar way (a repeat scan at least 7 days later when the mean sac diameter is under 25 mm).
NICE also asks clinicians to explain that a single scan cannot be 100 per cent accurate in diagnosing miscarriage, particularly very early on. That is why a repeat scan a week or more later is such a common, and sensible, recommendation.
A slow heart rate
Research shows that a slow heart rate early in the first trimester is linked with a higher chance of miscarriage, but it is not a certainty either way:
- In a large US study, 61 per cent of pregnancies with a slow heart rate at 6–7 weeks ended in first-trimester loss, compared with 9 per cent of those with a normal rate. Even when the rate had become normal by 8 weeks, the loss rate remained higher, at about 25 per cent, compared with about 7 per cent when the rate was normal at both scans. The authors recommended at least one follow-up scan later in the first trimester.
- Very slow rates (90 bpm or less before 8 weeks) have been linked with a high likelihood of miscarriage.
- At the very earliest stage (before about 6 weeks), a slower rate is less predictive. In one small study of embryos with a rate under 100 bpm at 5–6 weeks, more than half (20 of 36) survived the first trimester, especially when the embryo’s size matched the expected dates.
If your scan shows a slow heart rate, your clinician will usually suggest a follow-up scan to see how the heart rate and growth change over the next week or two. We will explain what we have seen, what the options are, and how to involve your NHS early pregnancy unit if needed.
Bleeding or pain
If you have bleeding or tummy pain in early pregnancy, the NHS advises getting advice promptly. Contact your maternity unit or local early pregnancy unit (available free on the NHS if you are under 20 weeks), or call NHS 111. Call 999 if you have heavy bleeding, severe tummy pain, shoulder-tip pain, or feel faint or dizzy. If you would also like a same-day private scan for reassurance, see our early pregnancy bleeding scan. Our miscarriage page explains what happens if a pregnancy is not continuing.
Your heart rate in pregnancy (maternal heart rate)
Pregnancy puts extra demands on your heart and circulation from very early on:
- Cardiac output (the amount of blood your heart pumps each minute) rises by around 40 per cent during pregnancy, and has already risen by about 20 per cent by 8 weeks.
- Blood volume increases by roughly 45 per cent. The NHS describes it as rising by up to 50 per cent.
- Resting heart rate rises too. Textbooks often quote a rise of 10–20 bpm, but recent evidence suggests the average rise is smaller (see below).
A 2019 review of studies in more than 8,000 healthy pregnancies found a smaller average rise than older textbooks suggested: about 8 bpm, with the mean maternal heart rate going from about 79 bpm at 10 weeks to about 87 bpm at 40 weeks. Individual women vary, so some will notice a bigger change than others.
Some people notice palpitations (a pounding, fluttering or irregular heartbeat) during pregnancy. The NHS advises seeing a GP if palpitations keep coming back, last more than a few minutes, or you have a heart condition or a family history of heart problems.
Call 999 or go to A&E if you have palpitations that do not go away, or palpitations with chest pain, shortness of breath or fainting.
Can the baby’s heart rate predict a boy or a girl?
It’s a popular myth that a heart rate above 140 bpm means a girl and a slower one means a boy. The evidence doesn’t support it. A study of 477 pregnancies scanned before 14 weeks found average heart rates of about 152 bpm for girls and 155 bpm for boys, which is not a meaningful difference. A 2023 review pooling five studies and more than 4,300 babies reached the same conclusion: first-trimester heart rate is not a dependable way to predict sex.
If you would like to know your baby’s sex, reliable options are a gender scan from 14 weeks or an early gender blood test (NIPT) from 9 weeks. Our post Baby boy or baby girl? covers more of the old wives’ tales.
Should I listen to my baby’s heartbeat at home?
Home Doppler devices are widely sold, but the NHS advises against using one to check on your baby. Hearing a heartbeat does not mean your baby is well, and it can falsely reassure you. Later in pregnancy, the more important sign is your baby’s pattern of movements. Contact your midwife or maternity unit straight away if your baby is moving less than usual, if you can no longer feel movements, or if the usual pattern changes.
How we check your baby’s heart at London Pregnancy Clinic
Ultrasound is an important tool for screening for congenital heart disease (CHD). CHD is a heart condition a baby is born with, and it is the most common group of congenital anomalies. A population study in the north of England found it in about 8 in every 1,000 live births. A national study of babies due in England in 2018–2020 found that around two-thirds of cases were diagnosed before birth, rising to more than 90 per cent for the most complex heart conditions. The NHS 20-week scan screens for serious cardiac abnormalities, but the NHS is clear that the scan cannot find every condition.
Our approach is to assess the baby’s heart function and development at every scan we do. Echocardiography, the examination of the fetal heart using ultrasound, is included with every scan where possible. From 12–18 weeks, our early fetal echocardiography scan looks at the heart in detail. Our fetal cardiac scan page explains how we examine the heart as part of our scans.
For the earliest weeks, see our guide to the 8 week scan, or compare all of our early pregnancy scans.
Key takeaways
- A heartbeat can often be seen on a transvaginal scan from around 6 weeks, but a healthy pregnancy can look “too early” if ovulation was late.
- The heart rate rises from roughly 100–130 bpm at 6 weeks to a peak of about 175 bpm at 9 weeks, then gradually settles to 110–160 bpm.
- If no heartbeat is seen or the rate is slow, NICE guidance means a repeat scan at least 7 days later is often the next step, rather than an immediate diagnosis.
- Your own heart rate usually rises a little in pregnancy, by about 8 bpm on average in a large 2019 review. Get urgent help for palpitations with chest pain, breathlessness or fainting.
- Heart rate cannot tell you whether you are having a boy or a girl.
This information is intended for general educational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional for guidance specific to your individual circumstances. If you have concerns about your pregnancy or baby’s wellbeing, contact your midwife, GP, or maternity unit promptly.
