Fetal Heart Rate Calculator

A fetal heart rate is expressed in beats per minute (bpm). The useful question is not just “what is the number?” but “when and how was it measured?” This calculator helps you choose the applicable context before it makes an interval comparison.

For a stable baseline during labour, 110–160 bpm is the usual reference interval. This is one part of a monitoring assessment, not a pass or fail test for a pregnancy. The NICE fetal monitoring guideline interprets the rate alongside the rest of the recording and clinical picture.

Why there is no universal fetal heart rate chart by week here

A table that labels 110–160 bpm normal from the earliest scan through birth would mix different settings. Early ultrasound research evaluated rates in gestational-age subgroups; it did not establish a single normal interval across all early weeks. See the Doubilet and Benson study of singleton pregnancies at 6–8 weeks. This page uses that evidence to explain the limitation, without turning study outcomes into personal predictions.

The calculator therefore does not invent weekly upper and lower limits. If your question comes from an early scan, use the gestational age on that report and ask the clinician what the scan as a whole shows. Our gestational age calculator can explain pregnancy dating, but an estimated date cannot replace clinical dating.

The 5–42 completed-week input limits and the term-only comparison are deliberate limits of this tool. They are not diagnostic boundaries. “No comparison” means this tool cannot interpret that context; it does not mean the rate is abnormal.

A CTG baseline is different from a momentary reading

Cardiotocography (CTG) records fetal heart rate and contractions over time. NICE defines the baseline from a stable 10-minute segment, leaving out accelerations and decelerations. A changing number on the monitor is not automatically that baseline. Ask the team which value to use; this calculator cannot calculate a baseline from a few numbers or a sound recording.

Below 110 bpm does not automatically imply an emergency diagnosis: NICE allows for certain stable 100–109 bpm baselines when other features are reassuring. Equally, a value inside the interval cannot clear a concerning trace. Variability, changes from earlier recordings and the wider clinical assessment matter. A sinusoidal pattern is a trace finding, which this single-value tool cannot identify. Read the NICE assessment criteria.

Worked examples you can reproduce

Select Load worked example for a confirmed baseline of 145 bpm at 39 weeks and 2 days. The age is 39 × 7 + 2 = 275 days, which is within this tool’s term-labour scope. Because 110 ≤ 145 ≤ 160, the output is within the reference interval. That statement does not assess fetal wellbeing.

Change the example to an 8-week ultrasound at 170 bpm and the tool gives no numerical comparison. Changing the context changes whether the reference applies. It does not change the recorded heart rate or turn it into a diagnosis.

What to take to your appointment

Keep the date and gestational age at the measurement, the recorded bpm, and whether it came from an ultrasound or a CTG baseline. Useful questions include: “Was that the baseline?”, “How does it fit the rest of the assessment?” and “Do I need any follow-up?” The pregnancy week calculator can help with a separate dating question.

If your baby’s usual movements have slowed, stopped or changed, call your midwife or maternity unit immediately. Hearing a heartbeat at home cannot confirm wellbeing, and you should not wait until the next day to seek advice. This advice applies regardless of a number shown here. NHS guidance on your baby’s movements.

Method and review status

This is a transparent interval comparison using NICE NG229, not a fetal risk model. It calculates gestational days and the distance outside the interval without rounding the value before comparison. No published clinical performance study or independent clinician review of this implementation is claimed. It does not estimate viability, diagnose bradycardia or tachycardia, predict fetal sex, analyse a CTG, or recommend treatment.

The page and examples were prepared on September 6, 2026. Its authorship describes software and educational content work; the linked sources supply the clinical reference. The original early-pregnancy study is included for context, not as a weekly prediction algorithm.