British Journal of Obstetrics and Gynaecology January 1979. Vol. 86. pp 4-9
NORMAL PATTERNS OF FETAL ACTIVITY IN THE THIRD TRIMESTER BY
A. B. ROBERTS, Rank Research Fellow
D. LITTLE, Research Registrar D. COOPER, ProgrammerlAnalyst AND
S . CAMPBELL, Professor Department of Obstetrics and Gynaecology, King’s College Hospital Medico1 School, London SE5
Summary The incidence and frequency of fetal respiratory movements (FRM) and fetal trunk movements (FTM) were measured in 21 normal pregnancies between 28 and 39 weeks gestation. Fetal activity was assessed with a real-time ultrasound scanner and all observed movements were punched directly onto computer tape. Recordings were made for one hour in three over a 24 hour period, providing a total of 168 hours for analysis. The overall mean percentage incidence of FRM was 31 per cent at a mean breathing rate of 43 breaths/minute. The mean percentage incidence of FRM during the day (0800-1759 hours) was 37 per cent. The overall mean percentage incidence of FTM was 18 per cent with a mean of 29 moves per 30 minute observation period. The mean percentage incidence of FTM during the day (0800-1759 hours) was 16 per cent. There was a well-defined circadian variation in fetal activity with FRM peaking between 1900 and 2200 hours, and FTM between 2200 and 0100 hours. There was considerable variation in the amount of FRM and FTM recorded from hour to hour. Total fetal activity rarely fell below 10 per cent in any one recording period and this measurement may be a more useful clinical test of fetal well-being than FRM or FTM alone. used to study fetal movement in the first trimester (Henner et al, 1975; Reinold, 1973; Jouppila, 1976; Kubli et al, 1976) and A-scan ultrasound systems have been used to study fetal respiration (Boddy and Dawes, 1975). There have been studies of fetal movement in the third trimester as assessed by real-time ultrasound (Roberts et al, 1977; Patrick, 1977), and short accounts of fetal respiratory movement (Marsal and Gennser, 1977; Patrick, 1977; Roberts et al, 1977; Manning, 1977; Lewis, 1977; Wladimiroff et al, 1977). These studies have led to the belief that
DUEto recent development in good resolution real-time ultrasound scanners, fetal activity can now be studied in detail. In the past, assumptions about fetal well-being had been made by more indirect methods. These included maternal perception of fetal movement (Pearson and Weaver, 1976; Sadovsky and Yaffe, 1973), observer palpation (Hems, 1973; Wood et a/, 1977), electromagnetic pressure sensors (Sadovsky and Yaffe, 1973), strain gauge devices (Wood et a/, 1977), tocodynometric transducers (Timor-Tritsch, 1976) and Piezo-electric crystals (Sadovsky et al, 1977). Ultrasound has been 4
FETAL ACTIVITY
reduced levels of fetal movement and fetal respiration are indicative of fetal hypoxia, and that absence of fetal movement or respiration is a sign of severe fetal distress that should be treated by immediate delivery of the fetus (Boddy and Dawes, 1975; Sadovsky and Yaffe, 1973; Pearson and Weaver, 1976). One of the major problems in interpreting the data is that there is insufficient information on the normal patterns of fetal activity during the third trimester. For this reason we investigated in detail the patterns of fetal body movement and fetal respiratory movement in normal pregnancy over a 24-hour study period. PATIENTS AND METHODS Twenty-one patients between 28 and 39 weeks menstrual age agreed to participate in the study. All patients were normal in that there were no complications of pregnancy, they were nonsmokers, took no drugs, were aged 18 to 32 years, and were all delivered of normal babies with no signs of fetal distress. All birth weights were between the 5th and 95th centile limits for gestational age (Thomson et al, 1968). Each patient was studied over a 24-hour period, starting at 1000 hours. The 24 hours were split into 8 three-hour sessions during which fetal respiratory movements (FRM) and fetal trunk movements (FTM) were observed for 45 to 60 ninutes using an ADR real-time scanner. The first ten patients were studied for two half hour sessions with a five minute interval between, during which samples of blood were taken. The last eleven patients were observed continuously for a period lasting between 45 and 60 minutes. We felt that 60 minutes was the maximum period a patient could be expected to lie in the same position. During the remainder of the 24 hours, the patients were encouraged to go about their normal activities as much as possible. The patients slept on a bed in the scanning room so that there was little disturbance to mother and fetus when the transducer was placed in position. The light was switched off or dimmed during the night and most women slept during the evening scanning session. Meals were taken at regular hospital times and no special diets were arranged. The transducer was placed on the mother’s abdomen and a view obtained of a transverse
5
section of the upper fetal abdomen. The women lay in a semi-recumbent position tilted to the right with a pillow. All respiratory movements and all body .movements of the fetus were recorded. Respiratory movements were easy to identify and consisted of rhythmical movements of the fetal chest and abdomen. Hiccup-type movements were also recorded and were defined as sharp movements of the fetal chest and abdomen associated with a generalized jerking of the body occurring in an irregular fashion. These movements were not recorded as breaths but were analysed separately by noting the time they started and the time they finished in a separate log. Isolated limb movements with no movements of the fetal trunk were not recorded although it was our impression that most significant limb movements of the fetus were associated with movements of the fetal body. Thus there were obviously some slight limb and head movements that were not observed. The transducer was held in place using a clamp designed and manufactured by Kretz Technic. Each observed breath was punched directly onto computer tape using a hand-held punch and the beginning and end of each fetal body movement was punched using a separate button. The tape was analysed by computer and fetal movements were calculated.
Fetal respiratory movements ( F R M ) Percentage incidence. The fetus was defined as ‘breathing’ when the respiratory rate was 10 breaths/minute or more, a gap of greater than six seconds between breaths was defined as the cessation of respiration. The incidence was expressed as a percentage of total observation time. Fetal respiratory rate. This was calculated by estimating the time interval between each successive breath (providing the gap was six seconds or less) and calculating an instantaneous fetal respiratory rate for each interval. This was plotted as a histogram but the results are presented here as the mean respiratory rate for each observation period. Reproducibility studies of the ultrasound method have been performed. Ten half hour video-tapes were analysed ‘blind’ by three separate observers and five half hour video-tapes
6
ROBERTS, LITTLE, COOPER AND CAMPBELL
were analysed three times by the same observer at intervals of greater than a week. With different observers the mean standard deviation in analysis of percentage time spent breathing was 1.99 per cent and with the same observer was 1.87 per cent.
RESULTS A total of 229 recordings of between 30 and 60 minutes were made in 21 patients, making an average of nearly 11 recordings per patient, and providing a total of 168 hours of recordings for analysis.
Fetal trunk movements (FTM) Percentage incidence. As the beginning and end of each movement period was punched, it was possible to measure the exact amount of time the fetal trunk was moving in any observation period and this was expressed as a percentage of the total observation time. Total number of fetal moves. This was calculated as the mean number of fetal moves per 30 minute observation period so that comparisons could be made between different patients at various times of the day. The mean standard deviation in an analysis of the percentage incidence of fetal movement was 1 a98 per cent with different observers and 1.25 per cent with the same observer. The mean standard deviation in an analysis of the number of moves was 5-03 moves per 30 minute study period with different observers and 3.04 moves with the same observer. Reproducibility for measurements of the number of moves is thus less good than for the percentage incidence, the coefficient of variation being 18 per cent with different observers and 9 per cent with the same observer.
FRM Percentage incidence. FRM were present for a mean of 31 per cent of the time. This ranged from 11 to 61 per cent over 24 hours and the range for an individual recording of 30 to 60 minutes was 0 to 92 per cent. There was a marked circadian rhythm in all 21 patients (Fig. 1) the incidence of FRM being least in the late evening and early morning and greatest in early evening. There was a statistically significant difference between the percentage incidence of FRM in the time period 0100 to 0400 hours and 1900 to 2200 hours (p < 0.001); and also between ‘day’ (37 per cent) and ‘night’ (23 per cent) (p 40.001). During the rest of the day, there was an increase in the ‘post-prandial’ incidence of FRM (41 per cent) (p 0*06). There was no significant difference in the mean respiratory rate between group A and group B.
FTM Percentage incidence. FTM were present for a mean of 18 per cent of the time, the range over a 24 hour period being from 11 to 26 per cent. The incidence in individual recordings varied between 1 and 54 per cent. There was a marked circadian rhythm in all patients (Fig. 2), the incidence of FTM being greatest in late evening and least around mid-day. There was a statistically significant difference between the percentage incidence of FTM in time period 1000 to 1300 hours compared to time period 2200 to 0100 hours (p
NORMAL PATTERNS OF FETAL ACTIVITY IN THE THIRD TRIMESTER BY
A. B. ROBERTS, Rank Research Fellow
D. LITTLE, Research Registrar D. COOPER, ProgrammerlAnalyst AND
S . CAMPBELL, Professor Department of Obstetrics and Gynaecology, King’s College Hospital Medico1 School, London SE5
Summary The incidence and frequency of fetal respiratory movements (FRM) and fetal trunk movements (FTM) were measured in 21 normal pregnancies between 28 and 39 weeks gestation. Fetal activity was assessed with a real-time ultrasound scanner and all observed movements were punched directly onto computer tape. Recordings were made for one hour in three over a 24 hour period, providing a total of 168 hours for analysis. The overall mean percentage incidence of FRM was 31 per cent at a mean breathing rate of 43 breaths/minute. The mean percentage incidence of FRM during the day (0800-1759 hours) was 37 per cent. The overall mean percentage incidence of FTM was 18 per cent with a mean of 29 moves per 30 minute observation period. The mean percentage incidence of FTM during the day (0800-1759 hours) was 16 per cent. There was a well-defined circadian variation in fetal activity with FRM peaking between 1900 and 2200 hours, and FTM between 2200 and 0100 hours. There was considerable variation in the amount of FRM and FTM recorded from hour to hour. Total fetal activity rarely fell below 10 per cent in any one recording period and this measurement may be a more useful clinical test of fetal well-being than FRM or FTM alone. used to study fetal movement in the first trimester (Henner et al, 1975; Reinold, 1973; Jouppila, 1976; Kubli et al, 1976) and A-scan ultrasound systems have been used to study fetal respiration (Boddy and Dawes, 1975). There have been studies of fetal movement in the third trimester as assessed by real-time ultrasound (Roberts et al, 1977; Patrick, 1977), and short accounts of fetal respiratory movement (Marsal and Gennser, 1977; Patrick, 1977; Roberts et al, 1977; Manning, 1977; Lewis, 1977; Wladimiroff et al, 1977). These studies have led to the belief that
DUEto recent development in good resolution real-time ultrasound scanners, fetal activity can now be studied in detail. In the past, assumptions about fetal well-being had been made by more indirect methods. These included maternal perception of fetal movement (Pearson and Weaver, 1976; Sadovsky and Yaffe, 1973), observer palpation (Hems, 1973; Wood et a/, 1977), electromagnetic pressure sensors (Sadovsky and Yaffe, 1973), strain gauge devices (Wood et a/, 1977), tocodynometric transducers (Timor-Tritsch, 1976) and Piezo-electric crystals (Sadovsky et al, 1977). Ultrasound has been 4
FETAL ACTIVITY
reduced levels of fetal movement and fetal respiration are indicative of fetal hypoxia, and that absence of fetal movement or respiration is a sign of severe fetal distress that should be treated by immediate delivery of the fetus (Boddy and Dawes, 1975; Sadovsky and Yaffe, 1973; Pearson and Weaver, 1976). One of the major problems in interpreting the data is that there is insufficient information on the normal patterns of fetal activity during the third trimester. For this reason we investigated in detail the patterns of fetal body movement and fetal respiratory movement in normal pregnancy over a 24-hour study period. PATIENTS AND METHODS Twenty-one patients between 28 and 39 weeks menstrual age agreed to participate in the study. All patients were normal in that there were no complications of pregnancy, they were nonsmokers, took no drugs, were aged 18 to 32 years, and were all delivered of normal babies with no signs of fetal distress. All birth weights were between the 5th and 95th centile limits for gestational age (Thomson et al, 1968). Each patient was studied over a 24-hour period, starting at 1000 hours. The 24 hours were split into 8 three-hour sessions during which fetal respiratory movements (FRM) and fetal trunk movements (FTM) were observed for 45 to 60 ninutes using an ADR real-time scanner. The first ten patients were studied for two half hour sessions with a five minute interval between, during which samples of blood were taken. The last eleven patients were observed continuously for a period lasting between 45 and 60 minutes. We felt that 60 minutes was the maximum period a patient could be expected to lie in the same position. During the remainder of the 24 hours, the patients were encouraged to go about their normal activities as much as possible. The patients slept on a bed in the scanning room so that there was little disturbance to mother and fetus when the transducer was placed in position. The light was switched off or dimmed during the night and most women slept during the evening scanning session. Meals were taken at regular hospital times and no special diets were arranged. The transducer was placed on the mother’s abdomen and a view obtained of a transverse
5
section of the upper fetal abdomen. The women lay in a semi-recumbent position tilted to the right with a pillow. All respiratory movements and all body .movements of the fetus were recorded. Respiratory movements were easy to identify and consisted of rhythmical movements of the fetal chest and abdomen. Hiccup-type movements were also recorded and were defined as sharp movements of the fetal chest and abdomen associated with a generalized jerking of the body occurring in an irregular fashion. These movements were not recorded as breaths but were analysed separately by noting the time they started and the time they finished in a separate log. Isolated limb movements with no movements of the fetal trunk were not recorded although it was our impression that most significant limb movements of the fetus were associated with movements of the fetal body. Thus there were obviously some slight limb and head movements that were not observed. The transducer was held in place using a clamp designed and manufactured by Kretz Technic. Each observed breath was punched directly onto computer tape using a hand-held punch and the beginning and end of each fetal body movement was punched using a separate button. The tape was analysed by computer and fetal movements were calculated.
Fetal respiratory movements ( F R M ) Percentage incidence. The fetus was defined as ‘breathing’ when the respiratory rate was 10 breaths/minute or more, a gap of greater than six seconds between breaths was defined as the cessation of respiration. The incidence was expressed as a percentage of total observation time. Fetal respiratory rate. This was calculated by estimating the time interval between each successive breath (providing the gap was six seconds or less) and calculating an instantaneous fetal respiratory rate for each interval. This was plotted as a histogram but the results are presented here as the mean respiratory rate for each observation period. Reproducibility studies of the ultrasound method have been performed. Ten half hour video-tapes were analysed ‘blind’ by three separate observers and five half hour video-tapes
6
ROBERTS, LITTLE, COOPER AND CAMPBELL
were analysed three times by the same observer at intervals of greater than a week. With different observers the mean standard deviation in analysis of percentage time spent breathing was 1.99 per cent and with the same observer was 1.87 per cent.
RESULTS A total of 229 recordings of between 30 and 60 minutes were made in 21 patients, making an average of nearly 11 recordings per patient, and providing a total of 168 hours of recordings for analysis.
Fetal trunk movements (FTM) Percentage incidence. As the beginning and end of each movement period was punched, it was possible to measure the exact amount of time the fetal trunk was moving in any observation period and this was expressed as a percentage of the total observation time. Total number of fetal moves. This was calculated as the mean number of fetal moves per 30 minute observation period so that comparisons could be made between different patients at various times of the day. The mean standard deviation in an analysis of the percentage incidence of fetal movement was 1 a98 per cent with different observers and 1.25 per cent with the same observer. The mean standard deviation in an analysis of the number of moves was 5-03 moves per 30 minute study period with different observers and 3.04 moves with the same observer. Reproducibility for measurements of the number of moves is thus less good than for the percentage incidence, the coefficient of variation being 18 per cent with different observers and 9 per cent with the same observer.
FRM Percentage incidence. FRM were present for a mean of 31 per cent of the time. This ranged from 11 to 61 per cent over 24 hours and the range for an individual recording of 30 to 60 minutes was 0 to 92 per cent. There was a marked circadian rhythm in all 21 patients (Fig. 1) the incidence of FRM being least in the late evening and early morning and greatest in early evening. There was a statistically significant difference between the percentage incidence of FRM in the time period 0100 to 0400 hours and 1900 to 2200 hours (p < 0.001); and also between ‘day’ (37 per cent) and ‘night’ (23 per cent) (p 40.001). During the rest of the day, there was an increase in the ‘post-prandial’ incidence of FRM (41 per cent) (p 0*06). There was no significant difference in the mean respiratory rate between group A and group B.
FTM Percentage incidence. FTM were present for a mean of 18 per cent of the time, the range over a 24 hour period being from 11 to 26 per cent. The incidence in individual recordings varied between 1 and 54 per cent. There was a marked circadian rhythm in all patients (Fig. 2), the incidence of FTM being greatest in late evening and least around mid-day. There was a statistically significant difference between the percentage incidence of FTM in time period 1000 to 1300 hours compared to time period 2200 to 0100 hours (p
