By Yianni Kiromitis u2014 PgC Medical Ultrasound, BSc (Hons). HCPC-registered Sonographer (RA38415)
Medically reviewed by Yianni Kiromitis, HCPC-registered Sonographer (RA38415) — 15 July 2026
Last reviewed: 15 July 2026
A baby's heart rate changes a lot in early pregnancy. It usually starts at around 90 to 110 beats per minute when it first becomes detectable u2014 typically around six weeks u2014 and rises quickly to a peak of around 150 to 170 beats per minute between nine and ten weeks. After that, it gradually settles into the range most people associate with pregnancy: 110 to 160 beats per minute from the second trimester onwards.
Understanding this arc helps make sense of what a sonographer tells you during an early scan. A heart rate that sounds very fast at eight weeks is not a cause for alarm u2014 it is exactly what a healthy eight-week heart should be doing.
The fetal heart rate arc in early pregnancy
The fetal heart begins beating at around five to six weeks of pregnancy, though it is often too faint to detect reliably before six weeks on an internal scan. The rate then rises steeply:
- 6 weeks: approximately 90u2013110 bpm u2014 just starting.
- 7 weeks: approximately 120u2013140 bpm u2014 rising.
- 8 weeks: approximately 140u2013160 bpm u2014 well established.
- 9u201310 weeks: approximately 150u2013170 bpm u2014 at or near peak.
- 11u201314 weeks: approximately 140u2013160 bpm u2014 beginning to settle.
- Second trimester onwards: approximately 110u2013160 bpm u2014 the normal range for the rest of pregnancy.
These are reference ranges, not exact targets. Individual variation is normal, and a single reading outside the range does not, on its own, indicate a problem.
Why the heart rate peaks at 9u201310 weeks
The rapid rise and then gradual fall in fetal heart rate during the first trimester reflects the development of the heart's own electrical conduction system. In the earliest weeks, the heart beats under the influence of the developing nervous system; as the conduction system matures, the rate stabilises. This is a normal part of cardiac development and is one of the reasons early scans are so informative.
What sonographers look for
During an early pregnancy scan, the sonographer will note the heart rate and compare it to the expected range for the gestational age. A rate that is very slow for the stage of pregnancy u2014 below about 90 bpm at six weeks, or below 100 bpm at seven weeks u2014 can be a sign that the pregnancy is not developing as expected, and a repeat scan is usually arranged. A rate that is very fast is rarely a concern in early pregnancy.
From our practice
The most common question I am asked after showing a heartbeat is "is that normal u2014 it sounds so fast?" At nine or ten weeks, a heart rate of 165 bpm is perfectly normal, and I enjoy explaining the arc to patients u2014 it usually transforms their anxiety into fascination. The heart rate is one of the most reassuring things we can show on an early scan, and seeing it for the first time is a moment most parents never forget. If you would like to see your baby's heartbeat, you can book an early pregnancy scan with us, or use our scan timing calculator to find the best time to come.
What is a normal fetal heart rate at 6 weeks?
At six weeks, the fetal heart rate is typically around 90 to 110 beats per minute. This is lower than it will be later in the first trimester, and reflects the very early stage of cardiac development.
What is a normal fetal heart rate at 8 weeks?
At eight weeks, the fetal heart rate is typically around 140 to 160 beats per minute. The rate is rising towards its peak, which occurs around nine to ten weeks.
Is 170 bpm too fast for a baby?
Not in early pregnancy. A heart rate of around 150 to 170 bpm is normal between nine and ten weeks, when the fetal heart rate is at its peak. After this, it gradually settles to the 110u2013160 bpm range seen in the second trimester.
What heart rate indicates a healthy pregnancy?
A heart rate within the expected range for the gestational age is reassuring. In early pregnancy, this means roughly 90u2013110 bpm at six weeks, rising to 150u2013170 bpm at nine to ten weeks, then settling to 110u2013160 bpm from the second trimester.
Can a slow heart rate be a sign of miscarriage?
A fetal heart rate that is significantly below the expected range for the gestational age can be a concerning sign, and a repeat scan is usually arranged. However, a single reading is never used to make a diagnosis u2014 context, gestational age, and repeat assessment all matter.
When can you first hear the heartbeat on a scan?
The heartbeat can usually first be detected on an internal (transvaginal) scan at around six weeks of pregnancy. On an abdominal scan, it may be a little later. Before six weeks, the heart may be beating but too faint to detect reliably.
Source: Standard sonographic reference values for fetal heart rate in early pregnancy. Practice pattern: IUS London early-pregnancy imaging team. Verified 14 July 2026.
