Computer Analysis of Fetal Heart Rate Variation During Normal Pregnancy

Abstract

Ninety-seven one-hour recordings of the abdominal fetal electrocardiogram (ECG) were made from 59 normal patients between 21 and 41 weeks of gestation. The heart intervals, measured between successive R-waves, were analysed by computer. The signal-to-noise ratio of the fetal ECG limited the precision of the interval measurements to approximately one millisecond. The characteristics of the baseline heart rate changed significantly as gestation advanced, the mean R-R interval, the standard deviation of the intervals and the standard deviation of the interval differences all increasing with gestation (p <0*001). In later gestation the baseline heart rate during periods of fetal rest differed significantly from that during periods of fetal activity; during rest the mean R-R interval was greater (p <0.001) and the standard deviations of the intervals and interval differences were smaller (p < 0.001). Examination of the coefficient of variation of the heart intervals gave a result which contradicted the significance of this measurement as an index of fetal welfare as proposed by Curran and MacGregor (1970).COMPUTER analysis of the fetal heart rate (FHR) can provide an objective means of condensing the large quantity of information which results from continuous monitoring of the fetus. In particular, a more accurate analysis of cardiac beat-to-beat variation can be obtained com-* Present address: Department of Obstetrics and Gynaecology, John Radcliffe Hospital, Headington, Oxford OX3 9DU. pared with that provided by conventional FHR monitors. The relatively slow recording speeds of the latter, combined with the small scales allowed for the display of the heart rate, make it difficult to distinguish the changes in rate from beat to beat. Furthermore the scales, being linear to frequency, compress the changes in heart interval at the lower rates and expand them at higher rates.Reliable observations of heart interval can 186

Influence of gestational age, heart rate, gender and time of day on fetal heart rate variability

“…We have recently reported similar results in a case of gestational hypertension (SCHIERMEIER et al, 2005). The dependency of FHRV on gestational age, confirmed in this work, has been previously documented (WHEELER et al, 1979;VAN LEEUWEN et al, 1999;WAKAI, 2004). Beyond this, our results demonstrate that, in the assessment of FHRV, it is essential to take the heart rate, i.e.…”

“…One of these factors could be fetal activity which is known to influence FHRV from the 28th week of gestation onwards (PILLAI and JAMES, 1990). This corresponds roughly to the increasing spread of the HRV measures after the 30th week of gestation that we and others have observed (WHEELER et al, 1979;VAN LEEUWEN et al, 1999;WAKAI, 2004).…”

“…WHEELER et al, 1979). In previous work examining measurements from the time domain as well as non-lineax measurements, we noted a substantial increase in the spread of the HRV values after the 30th week of gestation (VAN LEEUWEN et al, 1999).…”

Fetal heart rate and fetal heart rate variability in Lipizzaner broodmares

“…It is known from previous studies that the heart rate of the human fetus decreases from month to month with the advancement of pregnancy (Wheeler et al, 1979;van Leeuwen et al, 1999). Nagel et al (2010Nagel et al ( , 2011 have found that the same occurs in the equine fetus, with an increase of HRV during gestation.…”

“…In humans, the variability of fetal heart rate increases markedly in the third trimester of pregnancy. This can probably be attributed to the maturation of the vegetative nervous system which influences cardiac function (Wheeler et al, 1979;van Leeuwen et al, 1999).…”