VARIATION OF EMBRYONIC FETAL HEART-RATE AT 6-13 WEEKS GESTATION/

The aim of this study was to investigate changes in heart rate, namely the intraindividual variation, in normal embryos/fetuses between 6 an d 13 weeks' gestation. A prospective study was performed of 41 singlet on pregnancies undergoing routine ultrasound examination during the fi rst trimester of pregnancy. For each case, the embryonic/fetal heart r ate was measured on three consecutive occasions with a mean interval o f 4 min. The difference in heals' rate values between the serial measu rements varied from 0 to 18 beats/min and was significantly associated with gestational age (Spearman r = 0.26, p < 0.01). In the group of 1 5 fetuses (examined before 10 weeks' gestation), the difference betwee n measurements (median = 0 beats/min, range 0-8 beats/min) was signifi cantly lower (z=2.48, p < 0.05) than in fetuses assessed after 10 week s of gestation (median = 3, range 0-18 beats/min). Reliable and reprod ucible information concerning embryonic/fetal heart rate may be obtain ed from a single measurement, especially when pregnancies are examined before 10 weeks of gestation.