A study on changes in the fetal heart rate by gestational weeks

Abstract

We recorded the fetal heart rate 189 times in 89 normal pregnant women in 1982-1984 at the First Hospital of Nippon Medical School. The total time of the recordings amounted to 40 minutes. The recordings were studied and the following results were obtained.
1) Amplitude of fetal heart rate acceleration (FHR acceleration) increased as the gestational week advanced.
2) After 27 weeks of gestation, incidence of FHR acceleration with amplitude of more than 15 bpm increased, whereas that of FHR acceleration with amplitude of 10-15 bpm decreased. As a result, the total incidence of FHR acceleration remained constant.
3) As for fetal heart rate-baseline variability, it was found that as the gestational week progressed durations of both reduced and undulatory phases were prolonged. The same was true of durations of active and rest phases.
The above findings show that to obtain the information about the fetal heart rate is of significance in assessing the maturation of the fetus.