Predictive value of early embryonic cardiac activity for pregnancy outcome

The biologic variation of the embryonic heart rate was investigated by transvaginal ultrasonography during the first trimester of normal (n = 141) and abnormal (n = 29) pregnancies, and the predictive value of a repeatedly diagnosed slow heart rate for pregnancy outcome was determined. The mean heart rate increased from 82 +/- 10.3 beats/min at 5 weeks' gestation to 156 +/- 9.6 beats/min at 9 weeks. A single observation of an abnormally slow heart rate did not necessarily predict subsequent embryonic death. However, a continued decline in embryonic heart activity, observed within a few days' interval, was always associated with a first-trimester abortion.