Clinical experience with the Hewlett-Packard M-1350A fetal monitor: correlation of Doppler-detected fetal body movements with fetal heart rate parameters and perinatal outcome

Validity of the Hewlett-Packard actograph in detecting fetal movements

OBJECTIVE

To detect fetal movements during non-stressed cardiotocography to evaluate the validity of the Hewlett-Packard Doppler ultrasound actograph in detecting fetal movements.

METHODS

This was a prospective, observational study. Thirty healthy pregnant women were divided into two gestational age groups (Group I, 31 + 0 to 34 + 0 weeks, n = 15; Group II, 37 + 0 to 40 + 0 weeks, n = 15). A Hewlett-Packard M-1350-A actocardiograph was used to make recordings of 45 min for each woman. Fetal movements were also detected sonographically by an observer and they were recorded independently by the pregnant woman. Ninety consecutive 30-s periods were analyzed to study agreement between the three techniques.

RESULTS

The mean total agreement for fetal activity plus quiescence between ultrasound and the actograph was 63.7% for Group I, and 72.2% for Group II. In cases of fetal activity only, these values were 45.8% and 47.6%, respectively. Total agreements between ultrasound and the pregnant woman were 74.0% and 79.0%, respectively, for Groups I and II. Cohen's kappa values for total agreement between ultrasound and actograph were 0.31 (95% CI, 0.27-0.36), indicating 'fair' agreement in Group I, and 0.43 (95% CI, 0.38-0.47), indicating 'moderate' agreement in Group II.

CONCLUSIONS

Use of the Hewlett-Packard actograph may offer some additional information during routine cardiotocography. However, our results were disappointing; the technique appears not to be suitable for detailed recordings of fetal behavior, and may even be misleading when difficult cardiotocographic patterns have to be interpreted.

The effect of betamethasone versus dexamethasone on fetal biophysical parameters

BACKGROUND

Clinical observations suggest that betamethasone reduces maternal perception of fetal movements and short term variability, but that this dose not occur after treatment with dexamethasone.

OBJECTIVES

To compare the effect of betamethasone and dexamethasone on fetal biophysical parameters.

METHODS

In a randomized, prospective, double blind study, 20 courses of betamethasone and 20 courses of dexamethasone were given in random sequence to patients with imminent preterm labor. During the first 32h after initiation of treatment, fetal movements were counted by the mothers and recorded by ultrasound, and a nonstress test was performed.

RESULTS

Betamethasone induced a significant decrease in fetal movements as perceived by the mother and observed by ultrasound. Fetal breathing movements also decreased. Dexamethasone did not change fetal body movements. Neither drug changed the short term variability.

CONCLUSIONS

Unlike betamethasone, dexamethasone does not induce a decrease in fetal movements. Dexamethasone might, therefore, be preferred for enhancement of lung maturation in imminent preterm labor.

The DopFet system: a new ultrasonic Doppler system for monitoring and characterization of fetal movement

To enable the investigation of fetal movement in a manner similar to fetal heart rate (FHR) monitoring we have developed an apparatus (the DopFet system) that consists of a pair of miniature sensors, a 2-MHz continuous-wave directional Doppler electronic module and a laptop personal computer. One of the sensors is aimed at the fetal limbs and the other at the thorax to detect heart and upper body movements. The signals are analyzed, presented in real-time and postprocessed by software developed by us. The postprocessing software computes a number of parameters (the DopFet parameters) describing fetal movement. These parameters can be divided into two categories: parameters that describe the quantity of fetal movement (i.e., number of movements) and parameters that describe qualitative aspects of fetal movement (i.e., average movement duration). Future studies using the DopFet system will be aimed at discovering which of these parameters or combination of parameters is the best indicator of fetal well-being. We present an example of a 0.5 h recording and the results of testing on 23 volunteer mothers. These results show good sensitivity of the system compared to real-time ultrasound (US). The system detects 96% of rolling movements, 100% of flexion movements and 97% of leg movements.

Nonstress testing and contraction stress testing

Antepartum fetal heart rate (FHR) testing, including the nonstress test and contraction stress test, has evolved in clinical usage over the past 3 decades. Although the nonstress test has become a standard of care in high-risk pregnancy, it has been modified by the use of fetal stimulation (vibroacoustic stimulation) and the addition of automated fetal movement recording (actocardiotocography). In all of its formats, antepartum FHR testing has been associated with reduction of preventable fetal loss. More recently, there have been attempts to improve test efficacy by computer-enhanced approaches.

Fetal movement detection: comparison of the Toitu actograph with ultrasound from 20 weeks gestation

OBJECTIVE

This study evaluates the validity of Doppler-detected fetal movement by a commercially available monitor and investigates whether characteristics of maternal body habitus and the intrauterine environment affect its performance.

METHODS

Fetal movement was evaluated in normal pregnancies using both ultrasound visualization and a fetal actocardiograph (Toitu MT320; Tofa Medical Inc., Malvern, PA). Data were collected for 32 min on 34 fetuses stratified by gestational age (20-25 weeks; 28-32 weeks; 35-39 weeks). Fetal and maternal characteristics were recorded. Comparisons between ultrasound-detected trunk and limb movements and actograph records were conducted based both on 10-s time intervals and on detection of individual movements.

RESULTS

Time-based comparisons indicated agreement between ultrasound and actograph 94.7% of the time; this association rose to 98% when movements of less than 1 s duration were excluded. Individual movements observed on ultrasound were detected by the actograph 91% of the time, and 97% of the time when brief, isolated movements were excluded. The overall kappa value for agreement was 0.88. The actograph was reliable in detecting periods of quiescence as well as activity. These findings did not vary by gestational age. The number of movements detected by the actograph, but not the single-transducer ultrasound, significantly increased over gestation. Maternal age, parity, weight, height, or body mass index were not consistently associated with actograph validity. Characteristics of the uterine environment, including placenta location, fetal presentation, and amniotic fluid volume also did not affect results.

CONCLUSIONS

The Toitu actograph accurately detects fetal movement and quiescence from as early as 20 weeks gestation and has utility in both clinical and research settings. Actographs are most useful for providing objective and quantifiable measures of fetal activity level, including number and duration of movements, while visualization through ultrasound is necessary for studies of movement quality, source, or mechanics.

Antepartum testing

Among the methods of antepartum testing in use today, the nonprovocative tests (NST, BPP, MBPP) are safe and effective for use in ambulatory settings. Outpatient or office utilization of the CST is limited by the need for intravenous access (when oxytocin is used) and by the potential for uterine hyperstimulation and resultant acute FHR abnormalities. Regardless of the method of testing used, large studies have confirmed that the fetal death rate among patients undergoing antepartum testing is significantly lower than that in the general, untested population. This is a particularly encouraging observation in view of the fact that antepartum testing is used almost exclusively in complicated pregnancies at highest risk for poor outcome. In the future, protocols using adjunctive testing methods (fetal movement counting, fetal movement profile, Doppler velocimetry) in combination with standard methods (CST, NST, BPP, MBPP) may further reduce the incidence of fetal death in high-risk populations. At present, the beneficial effects of antepartum testing have created a situation in which the likelihood of fetal death in high-risk, tested populations is lower than that in low-risk, untested populations. This paradox will force us to consider the option of routine antepartum testing in all pregnancies.

Fetal and maternal diurnal rhythms during the third trimester of normal pregnancy: outcomes of computerized analysis of continuous twenty-four-hour fetal heart rate recordings

OBJECTIVE

We quantified the presence of diurnal rhythms in various computerized fetal heart rate parameters in normal pregnancies to assess their clinical relevance.

STUDY DESIGN

Modified cosine analysis was applied to the outcomes of computerized analysis of continuous 24-hour fetal heart rate recordings in 26 normal pregnancies. Diurnal rhythms in maternal heart rate and plasma hormones were assessed in 15 and 17 pregnancies, respectively. Correlations between maternal and fetal rhythms were calculated.

RESULTS

A significant diurnal rhythm in basal heart rate was present in 73% of the fetuses and was closely related to the maternal heart rate rhythm. Diurnal rhythms in heart rate variability, accelerations, and activity were present in only 30% to 50% of the fetuses.

CONCLUSIONS

The mother entrains fetal diurnal rhythms. The normal variability in neural development may account for the absence of diurnal rhythms in some fetuses.

Developments in CTG analysis

FHR monitoring has been the subject of many debates. The technique, in itself, can be considered to be accurate and reliable both in the antenatal period, when using the Doppler signal in combination with autocorrelation techniques, and during the intrapartum period, in particular when the FHR signal can be obtained from a fetal ECG electrode placed on the presenting part. The major problems with FHR monitoring relate to the reading and interpretation of the CTG tracings. Since the FHR pattern is primarily an expression of the activity of the control by the central and peripheral nervous system over cardiovascular haemodynamics, it is possibly too indirect a signal. In other specialities such as neonatology, anaesthesiology and cardiology, monitoring and graphic display of heart rate patterns have not gained wide acceptance among clinicians. Digitized archiving, numerical analysis and even more advanced techniques, as described in this chapter, have primarily found a place in obstetrics. This can be easily explained, since the obstetrician is fully dependent on indirectly collected information regarding the fetal condition, such as (a) movements experienced by the mother, observed with ultrasound or recorded with kinetocardiotocography (Schmidt, 1994), (b) perfusion of various vessels, as assessed by Doppler velocimetry, (c) the amount of amniotic fluid or (d) changes reflected in the condition of the mother, such as the development of gestation-induced hypertension and (e) the easily, continuously obtainable FHR signal. It is of particular comfort to the obstetrician that a normal FHR tracing reliably predicts the birth of the infant in a good condition, which makes cardiotocography so attractive for widespread application. However, in the intrapartum period, many traces cannot fulfil the criteria of normality, especially in the second stage. In this respect, cardiotocography remains primarily a screening and not so much a diagnostic method. As long as continuous monitoring of fetal acid-base balance has not been extensively tested in clinical practice, microblood sampling of the fetal presenting part (Saling, 1994) is a useful adjunct. The problem with non-normal tracings is that their significance is very often unclear. They may indicate serious fetal distress, finally resulting in preventable destruction of critical areas in the fetal brain and damage to various organs; or, on the contrary, they may indicate temporary changes in cardiovascular control as a reaction to the intermittent effects on fetal haemodynamics of, for example, uterine contractions, whether or not in combination with partial or complete compression of umbilical cord vessels or the vessels on the chorionic plate (van Geijn, 1994). Many factors influence the FHR and its variability, which further complicates the interpretation of FHR patterns; some have been discussed here in some detail. Undoubtedly, there is a need for quantitative and objective FHR analysis, as long as it does not lead to erroneous results. Close collaboration between engineers and clinicians is a prerequisite for further advances in this field. Decision support systems certainly have a future but only if they are able to take into account a large set of clinical data and can combine it with data obtained from FHR signals and other parameters referring to the fetal condition, such as fetal growth, Doppler velocimetry, amniotic fluid volume and biochemical and biophysical data obtained from the mother. Basic technical concepts inherent in computerized CTG analysis, such as sampling rate (Chang et al, 1995), signal loss, artefact detection (van Geijn et al, 1980), further processing of intervals, archiving in digitized format and monitor display, should receive considerable attention. There is still a long way to go until decision support systems find their way into obstetric practice. Further developments can only be achieved thanks to efforts of many basic and clinical researchers, wo

Time-quantified fetal movement detection with two-transducer data fusion

OBJECTIVE

Our purpose was to develop an automated ultrasound-based fetal movement detection system to better define fetal movements.

STUDY DESIGN

One hundred one patients had fetal movements recorded over a 20-minute period. Results of movement detection by a single-transducer system (Russell 1) and a two-transducer fusion system (Russell 2) were compared with those of Hewlett-Packard (HP-M-1350-A), maternal perception, and expert ultrasonography review.

RESULTS

A total of 86,592 seconds of videotape was scored for fetal movement. Russell 2 had a second-per-second sensitivity of 57.21% compared with Russell 1 at 40.95%, the HP-M-1350-A at 31.44%, and maternal perception at 30.80%. Russell 2 detected 67.57% of discrete movements compared with 57.52%, 41.98%, and 37.92%, respectively, in other systems.

CONCLUSION

Russell 2 represents a significant improvement over existing systems in detection of fetal movements on a second-per-second basis.