[Normal values of fetal heart rate in the 5th to 18th weeks of pregnancy (in vivo and in vitro studies)].

The normal values of the foetal heart rate (FHR) in early pregnancy were determined in utero by Doppler ultrasound technique and in vitro on isolated, in nutrient solution surviving, foetal hearts obtained from termination of pregnancy. The early heart rate was found to be surprisingly high in 354 successful ultrasonic examinations. In the eighth week the average FHR was 178 min-1. In the course of pregnancy there was a gradual decrease in FHR and in the 17th-18th week it reached 140 min-1 characteristic of the human foetus. Similar data were obtained under in vitro conditions.