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The Endowment for Human Development
The Endowment for Human Development
Improving lifelong health one pregnancy at a time.
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Circadian Rhythms


4 months, 3 weeks

From The Biology of Prenatal Development.Buy Now

Script: From 19 weeks fetal movement, breathing activity, and heart rate begin to follow daily cycles called circadian rhythms.

All ages referenced to fertilization, not last menstrual period. One month = 4 weeks.
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