Cardiovascular System - Heart Rate Development

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Heart rate (beats / minute) is a measurement that can be made from early in development (when the heart first starts) through embryonic and fetal stages into labor and birth. It is a common clinical diagnostic tool, but data can be variable between countries and institutions.

Early ultrasonographic measurement of embryonic heart rate (EHR) shows a steady increase from Stage 9-10 (75 beats/minute) to Stage 18 (130 beats/minute) and on to Stage 20, following which a gradual decrease in EHR occurs (More? Embryonic Heart Rate). This increase correlates with heart development and a low EHR is used as an indicator of developmental failure and likely abortion. Late stethoscope measurements of fetal heart rate can monitor fetal stress and identifies the characteristic "lub-dub" heart valve sounds.

Links: 2009 Lecture - Early Vascular Development | 2009 Lecture - Heart | Cardiovascular System Development | Student Project - ILP Heart Embryology Education | OMIM selected abnormality entries | Embryonic Heart Rate original page


  • Human Embryology (2nd ed.) Larson Ch7 p151-188 Heart
  • The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Ch14: p304-349
  • Before we Are Born (5th ed.) Moore and Persaud Ch12; p241-254
  • Essentials of Human Embryology Larson Ch7 p97-122 Heart
  • Human Embryology Fitzgerald and Fitzgerald Ch13-17: p77-111

Embryonic Heart Rate

In a later study by Coulam etal. (1996), normal successful human gestations were defined by EHR criteria at different early embryonic (34-56 days from last menstrual period) developmental stages (at the earliest stages when embryo length is difficult to measure gestational sac diameters are included). Coulam CB, Britten S, Soenksen DM. Early (34-56 days from last menstrual period) ultrasonographic measurements in normal pregnancies. Hum Reprod. 1996 Aug;11(8):1771-4.

  • Stage 9-10 2 mm embryo (gestational sac diameter of 20 mm) EHR at least 75 beats / minute
  • Stage 11-12 5 mm embryo (gestational sac diameter of 30 mm) EHR at least 100 beats / minute
  • Stage 16 10 mm embryo EHR at least 120 beats / minute
  • Stage 18 15 mm embryo EHR at least 130 beats / minute

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Cite this page: Hill, M.A. (2019, December 8) Embryology Cardiovascular System - Heart Rate Development. Retrieved from

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© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G