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Slow Heartbeat at 6 Weeks: What's Normal?

Hearing that your baby's heartbeat is "slow" at 6 weeks can be alarming, but it's actually quite common and often resolves on its own. Here's what you need to know about fetal heart rates in very early pregnancy.

Table of Contents

  1. What's a Normal Heart Rate at 6 Weeks?
  2. Why the Heartbeat Might Be Slow
  3. What Heart Rate Is Concerning?
  4. What Happens Next
  5. Will a Slow Heartbeat Catch Up?
  6. How to Cope While Waiting

What's a Normal Heart Rate at 6 Weeks?

The fetal heart begins beating at about 5+5 to 6+1 weeks, starting at roughly **80-90 beats per minute (bpm)**. It then accelerates by about 3 bpm per day, reaching:
  • 6 weeks: 90-110 bpm (normal range)
  • 7 weeks: 120-150 bpm
  • 8 weeks: 150-170 bpm
  • 9-10 weeks: 170-180 bpm (peak)

At 6 weeks, a heart rate of 90-110 bpm is normal. The heart has only just started beating, so it's naturally slower than it will be in a week or two. The rate increases rapidly as the heart develops and the baby grows.

Why the Heartbeat Might Be Slow

There are several reasons a heartbeat might be slow at 6 weeks:
  • The heart has only just started beating: If the heart began beating at 5+5 or 6+0, it will be slow at first. It needs a few days to speed up to its normal rate.
  • You're earlier than you think: If you're actually 5+4 rather than 6+2, the heart may not have started beating yet or may have only just started, giving a slow reading.
  • Measurement difficulty: At 6 weeks, the baby is so tiny that measuring the heart rate accurately is challenging. The reading may not be perfectly accurate.
  • Transient slowing: Sometimes the heart rate fluctuates in very early pregnancy. A single slow reading doesn't always reflect the true rate.

What Heart Rate Is Concerning?

Research suggests the following thresholds for concern at 6 weeks:
  • Below 80 bpm: This is considered bradycardia (slow heart rate) and warrants a repeat scan. About 50-60% of babies with a heart rate below 80 bpm at 6 weeks go on to miscarry, but 40-50% survive — so it's not a death sentence.
  • 80-100 bpm: This is borderline. The heart may have only just started beating. A repeat scan in 7-10 days will usually show an increased rate.
  • 100-110 bpm: This is within the normal range for 6 weeks. Not concerning.
  • Above 110 bpm: This is on the faster side for 6 weeks but still normal. The heart rate accelerates quickly at this stage.

The key message is that a slow heart rate at 6 weeks is not definitive. Many babies with initially slow heartbeats go on to have normal heart rates at their repeat scan.

What Happens Next

If the heart rate is slow at 6 weeks, the sonographer will:
  1. Note the heart rate: They'll tell you the number and explain what it means.
  2. Measure the CRL: If the baby is smaller than expected, you may be earlier than your dates suggest, which would explain the slow rate.
  3. Arrange a repeat scan: Usually in 7-10 days. By then, the heart rate should have increased if the pregnancy is progressing.
  4. Advise on symptoms: Watch for bleeding, cramping, or loss of pregnancy symptoms (nausea, breast tenderness). Report any changes to your GP or EPU.

The sonographer won't diagnose a miscarriage from a single slow heart rate reading. A repeat scan is always needed to see whether the rate has increased and the baby has grown.

Will a Slow Heartbeat Catch Up?

In many cases, yes. Studies show that:
  • About 50-60% of babies with a heart rate below 80 bpm at 6 weeks go on to miscarry.
  • About 40-50% survive and the heart rate normalises.
  • For heart rates of 80-100 bpm, the survival rate is higher — around 70-80%.
  • If the slow heart rate is due to a dating error (you're earlier than expected), the outlook is even better.

The repeat scan will give you the answer. If the heart rate has increased to a normal level and the baby has grown, everything is fine. If the heart rate has stayed slow or the baby hasn't grown, that's more concerning.

How to Cope While Waiting

- **Don't obsess over the number**: A single heart rate reading at 6 weeks doesn't define your pregnancy's outcome. Wait for the repeat scan. - **Avoid Googling**: The statistics online can be frightening, but they don't apply to every case. Your situation is unique. - **Watch for symptoms**: If you're still feeling nauseous and your breasts are tender, that's a good sign your hormone levels are normal. - **Talk to someone**: Share your worry with your partner or a friend. Don't carry it alone. - **Take care of yourself**: Rest, eat well, and be gentle with yourself.

Frequently Asked Questions

### What's the survival rate for a slow heartbeat at 6 weeks?

It depends on the heart rate. Below 80 bpm, about 40-50% of pregnancies survive. For 80-100 bpm, the survival rate is around 70-80%. For 100+ bpm, the outlook is very good.

Should I be worried if my symptoms have disappeared?

Loss of pregnancy symptoms (nausea, breast tenderness) can be a sign of miscarriage, but symptoms also naturally fluctuate. If you're worried, contact your EPU — they may bring your repeat scan forward.

Can I do anything to help the heart rate increase?

No. The heart rate is determined by the baby's development, which you can't influence. If the pregnancy is viable, the heart rate will increase on its own. If it isn't, nothing you did caused it.

Further reading:

This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider.

Last reviewed: June 2026

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