Introduction
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.
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<html5media height="280" width="320">File:Chicken_heartloop 01.mp4</html5media>
Click Here to play on mobile device
Chicken embryo heart beat. Normal Chick Heart Movie
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Some Recent Findings
- Antenatal cardiotocography for fetal assessment[1] "Cardiotocography (CTG) is a continuous recording of the fetal heart rate obtained via an ultrasound transducer placed on the mother's abdomen. CTG is widely used in pregnancy as a method of assessing fetal well-being, predominantly in pregnancies with increased risk of complications. ...There is no clear evidence that antenatal CTG improves perinatal outcome, but further studies focusing on the use of computerised CTG in specific populations of women with increased risk of complications are warranted."
- Normal Ranges of Embryonic Length, Embryonic Heart Rate, Gestational Sac Diameter and Yolk Sac Diameter at 6-10 Weeks [2] "We examined 4,698 singleton pregnancies with ultrasound measurements of CRL, HR, GSD and YSD at 6-10 weeks and CRL at 11-13 weeks resulting in the live birth after 36 weeks of phenotypically normal neonates with birth weight above the 5th centile. Gestational age was derived from CRL at the 11- to 13-week scan using the formula of Robinson and Fleming."
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Textbooks
- 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 1996 study 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). [3]
- 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
Ultrasound Measurement
This movie is a realtime ultrasound recording of the week 12 fetus. The bottom window shows doppler analysis to measure the fetal heart rate.
- Links: Quicktime | Flash
References
- ↑ <pubmed>23235650</pubmed>
- ↑ <pubmed>20847544</pubmed>
- ↑ <pubmed>8921130</pubmed>
Reviews
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Articles
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Cite this page: Hill, M.A. (2024, March 29) Embryology Cardiovascular System - Heart Rate Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Cardiovascular_System_-_Heart_Rate_Development
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- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G