A normal fetal heart rate (FHR) usually ranges from 120 to 160 beats per minute (bpm) in the in utero period.
Evolution through gestation
Although the myocardium begins to contract rhythmically by 3 weeks following conception (from spontaneously depolarising myocardial pacemaker cells in the embryonic heart) it is first visible on sonography around 6 weeks of gestation where is usually around 100 to 120 beats per minute (bpm).
This then increases progressively over the subsequent 2-3 weeks becoming 7
- ~110 bpm (mean) by 5-6 weeks
- ~170 bpm by 9-10 weeks
This is followed by a decrease becoming on average.
- ~150 bpm by 14 weeks
- ~140 bpm by 20 weeks
- ~130 bpm by term
Although the healthy fetus the heart rate is usually regular, a beat-to-beat variation of approximately 5 to 15 beat per minute can be allowed.
A slow fetal heart rate is termed a fetal bradycardia and is usually defined as 1
- a heart rate below 100 bpm before 6.3 weeks gestation, or
- a heart rate below 120 bpm between 6.3 and 7.0 weeks
A rapid fetal heart rate is termed a fetal tachycardia and is usually defined as
- a heart rate above 160-180 bpm 5,7
- a rate around 170 bpm may be classified as a borderline fetal tachycardia
- 1. Doubilet PM, Benson CB, Chow JS. Outcome of pregnancies with rapid embryonic heart rates in the early first trimester. AJR Am J Roentgenol. 2000;175 (1): 67-9. AJR Am J Roentgenol (full text) - Pubmed citation
- 2. Doubilet PM, Benson CB. Embryonic heart rate in the early first trimester: what rate is normal? J Ultrasound Med. 1995;14 (6): 431-4. J Ultrasound Med (abstract) - Pubmed citation
- 3. Benson CB, Doubilet PM. Slow embryonic heart rate in early first trimester: indicator of poor pregnancy outcome. Radiology. 1994;192 (2): 343-4. Radiology (abstract) - Pubmed citation
- 4. Doubilet PM, Benson CB. Outcome of first-trimester pregnancies with slow embryonic heart rate at 6-7 weeks gestation and normal heart rate by 8 weeks at US. Radiology. 2005;236 (2): 643-6. doi:10.1148/radiol.2362040880 - Pubmed citation
- 5. Oudijk MA, Visser GH, Meijboom EJ. Fetal tachyarrhythmia--part I: Diagnosis. Indian Pacing Electrophysiol J. 2004;4 (3): 104-13. Indian Pacing Electrophysiol J (link) - Free text at pubmed - Pubmed citation
- 6. Laboda LA, Estroff JA, Benacerraf BR. First trimester bradycardia. A sign of impending fetal loss. J Ultrasound Med. 1989;8 (10): 561-3. J Ultrasound Med (abstract) - Pubmed citation
- 7. Hornberger LK, Sahn DJ. Rhythm abnormalities of the fetus. Heart. 2007;93 (10): 1294-300. doi:10.1136/hrt.2005.069369 - Free text at pubmed - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Embryonal heart rate||✗|
|Foetal heart rate||✗|
|Embryonic heart rate||✗|
|Embryonic heart rate (EHR)||✗|