Fetal Heart Rate by Week: What's Normal?
Your baby's heart rate changes throughout pregnancy, starting slow and rapidly accelerating before gradually settling. Understanding what's normal at each stage can help you make sense of what the sonographer tells you.
Table of Contents
- How the Fetal Heart Rate Changes
- Heart Rate by Week Chart
- Why the Rate Changes
- What a Slow Heart Rate Means
- What a Fast Heart Rate Means
- How the Heart Rate Is Measured
- Old Wives' Tales About Heart Rate
How the Fetal Heart Rate Changes
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 remarkably quickly — about 3 bpm per day — reaching a peak of 170-180 bpm around 9-10 weeks. After that, it gradually slows down to settle at 120-160 bpm for the rest of the pregnancy.This pattern is completely normal. Your baby's heart needs to beat fast in early pregnancy because the heart is simple and the blood vessels are small — a faster rate circulates blood more effectively. As the heart develops and becomes more efficient, the rate slows.
Heart Rate by Week Chart
Here's a detailed guide to normal fetal heart rates by gestational age:| Gestational Age | Normal Heart Rate | Notes |
|---|---|---|
| 5+5 to 6+0 | 80-90 bpm | Heart just starting to beat |
| 6+1 to 6+3 | 90-100 bpm | Rate accelerating |
| 6+4 to 6+6 | 100-120 bpm | Continuing to accelerate |
| 7+0 to 7+6 | 120-150 bpm | Clearly visible on scan |
| 8+0 to 8+6 | 150-170 bpm | Approaching peak |
| 9+0 to 10+0 | 170-180 bpm | Peak heart rate |
| 10+1 to 11+0 | 160-175 bpm | Starting to slow |
| 11+1 to 12+0 | 150-170 bpm | Gradually slowing |
| 12+1 to 14+0 | 140-170 bpm | Settling into second-trimester range |
| Second trimester | 120-160 bpm | Stable for rest of pregnancy |
These ranges are based on medical research and NHS guidelines. Individual variations are normal — a reading slightly outside the range doesn't always mean a problem.
Why the Rate Changes
Several factors influence the fetal heart rate:- Gestational age: The biggest factor. The heart rate follows a predictable curve, as shown above.
- Baby's activity: When the baby moves, the heart rate can briefly increase (this is the basis of later CTG monitoring).
- Maternal factors: Your own heart rate, stress levels, and medications can have a small effect on the baby's rate.
- Measurement timing: The heart rate can fluctuate slightly throughout the day. A single reading is a snapshot, not a constant.
What a Slow Heart Rate Means
A heart rate that's below the normal range for the gestational age is called **bradycardia**. What it means depends on when it's detected:- At 6 weeks: A rate below 80 bpm is concerning but not definitive. About 40-50% of these pregnancies survive. A repeat scan will show whether the rate has increased.
- At 7-8 weeks: A rate below 100 bpm is more concerning. The heart should have accelerated by this stage. A repeat scan is essential.
- After 10 weeks: A rate below 120 bpm is unusual and warrants investigation by a fetal medicine specialist.
If you're told your baby's heart rate is slow, the sonographer will arrange a repeat scan. Don't panic — the repeat scan often shows a normal rate.
What a Fast Heart Rate Means
A heart rate above the normal range is called **tachycardia**. In early pregnancy:- Before 10 weeks: A rate above 180 bpm is unusual but can be normal near the peak. It may simply mean you're at the peak stage (9-10 weeks).
- After 10 weeks: A sustained rate above 180 bpm is unusual and may indicate fetal distress or a heart rhythm problem. This is rare and would be investigated by a specialist.
Most "fast" readings in early pregnancy are simply because you're near the 9-10 week peak. The sonographer will consider the gestational age when interpreting the rate.
How the Heart Rate Is Measured
The fetal heart rate can be measured several ways:- Ultrasound (M-mode): The most common method in early pregnancy. The sonographer uses ultrasound to measure the heart rate electronically. This is standard at all early scans.
- Doppler: A handheld device that detects the heartbeat using sound waves. This is used from about 12 weeks onwards in midwife appointments.
- CTG (cardiotocography): Used in later pregnancy to continuously monitor the heart rate. Not used in the first trimester.
At your scan, the sonographer will use M-mode ultrasound, which gives an accurate reading in seconds.
Old Wives' Tales About Heart Rate
There's a persistent myth that the fetal heart rate can predict your baby's gender — that a rate above 140 bpm means a girl and below 140 means a boy. This is **not supported by any evidence**. Studies have repeatedly shown no correlation between fetal heart rate and gender.The heart rate in early pregnancy is determined by gestational age and the baby's development, not by whether they're a boy or a girl. Don't use the heart rate to guess the gender — it won't give you a reliable answer.
Frequently Asked Questions
### What's a normal fetal heart rate at 12 weeks?At 12 weeks, a normal fetal heart rate is typically between 150 and 170 bpm. The rate is starting to slow down from its peak at 9-10 weeks.
Can the heart rate predict miscarriage?
A very slow heart rate (below 80 bpm at 6 weeks, below 100 bpm at 7-8 weeks) increases the risk of miscarriage, but it doesn't guarantee it. A repeat scan is needed to see whether the rate has normalised.
Does my heart rate affect my baby's?
Not directly. Your baby's heart rate is controlled by their own developing cardiovascular system. However, severe maternal stress or certain medications can have a small indirect effect.
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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