FETAL HEART RATES AS DETERMINED BY SONAR IN EARLY PREGNANCY

Abstract

Summary Using a pulsed ultrasound technique, the human fetal heart rate was studied between 45 days and 15 weeks after the first day of the last menstrual period. The heart rate rose from a level of 123 beats per minute at 45 days to a peak of 177 beats per minute at 9 weeks, and then gradually fell to a value of 147 beats per minute at 15 weeks. In cases of threatened abortion the fetal heart rates were not statistically different from those in normal pregnancies. The changes in heart rate were correlated with the morphological and physiological changes which occur in the fetal heart during this period.