High Fetal Heart Rate Variation Research Articles

Is lower fetal heart rate variability a susceptibility marker to the impact of negative coparenting on infant regulatory capacity?

Lower fetal heart rate variability (FHRV) may be a prenatal endophenotypic susceptibility marker and increase the impact of both positive and negative coparenting on infant regulatory capacity. This study analyzed the moderator role of FHRV in the association between positive and negative coparenting and infant regulatory capacity at 3 months. The sample comprised 86 first-born infants and their mothers and fathers recruited at a public Health Service in Northern Portugal. FHRV was recorded during routine cardiotocography examination at the third trimester of gestation. Mothers and fathers reported on coparenting and infant regulatory capacity at 2 weeks and 3 months postpartum. FHRV moderated the association between mother's and father's negative coparenting at 2 weeks postpartum and infant regulatory capacity at three months. Infants with low FHRV presented higher regulatory capacity when mothers or fathers reported less negative coparenting, while lower regulatory capacity when mothers or fathers reported more negative coparenting, than infants with high FHRV. Findings suggested lower FHRV as a prenatal endophenotypic susceptibility marker that increases the impact of negative coparenting on infant regulatory capacity.

Analysis of the results of a retrospective cohort study of the course of pregnancy, childbirth and the postpartum period in high-risk patients to identify factors of unfavorable outcomes and build a predictive model of fetal loss

Prenatal prognosis is an important part of obstetric care, which aims to reduce fetal and neonatal losses. A differentiated approach to the management of different risk groups allows you to optimize existing approaches.The objective: to identify antenatal factors that correlate with perinatal losses, by conducting a retrospective cohort study of women at high perinatal risk, to build a multifactorial prognostic model of adverse pregnancy outcomes.Materials and methods. A retrospective cohort study was conducted from 2014 to 2016 on the basis of the medical center LLC «Uniclinic», Medical Genetics Center «Genome», Clinic of Reproductive Genetics «Victoria», Kyiv City Maternity Hospital №2. 2154 medical cards of pregnant women from the group of high perinatal risk were selected and analyzed. Of these, 782 pregnant women were included in the final protocol after verification of compliance with the criteria.Results. Cesarean delivery occurred in 115 cases (14.7%). In 50 cases (6.4%) the caesarean section was performed in a planned manner, in 65 (8.3%) – in an emergency. In 39 (5%) cases, the indication for surgical delivery was acute fetal distress. Antenatal fetal death occurred in 11 (1.4%) cases: one case in terms of <34 weeks and <37 weeks of gestation, the remaining 9 cases – in terms of> 37 weeks. Intranatal death of two fetuses (0.3%) was due to acute asphyxia on the background of placental insufficiency. In the early neonatal period, 14 (1.8%) newborns died. Hospitalization of the newborn to the intensive care unit for the first 7 days was registered in 64 (8.2%) cases.The need for mechanical ventilation was stated in 3.96% (31/782) of newborns. The method of construction and analysis of multifactor models of logistic regression was used in the analysis of the relationship between the risk of perinatal losses (antenatal death, intranatal death, early neonatal death) and factor characteristics.Conclusion. Signs associated with the risk of perinatal loss: the presence of chronic hypertension, preeclampsia in previous pregnancies, type of fertilization (natural or artificial), the concentration of PAPP-A (MoM), the concentration of free β-HCG (MoM) in the second trimester, average PI in the uterine arteries in 28–30 weeks of pregnancy, PI in the middle cerebral arteries in 28–30 weeks of pregnancy, episodes of low fetal heart rate variability in the third trimester of pregnancy, episodes of high fetal heart rate variability in the third trimester of pregnancy. The model, built on selected features, allows with a sensitivity of 73.1% (95% CI: 52.2% – 88.4%) and a specificity of 72.7% (95% CI: 69.3% – 75.9%) to predict risk perinatal loss.

Antepartum high-frequency fetal heart rate sinusoidal rhythm: computerized detection and fetal anemia

Our aim was to identify antepartum fetal heart rate (FHR) records of high-frequency (HF) sinusoidal rhythms from an electronic database (1983-2003) and determine clinical outcomes. At the John Radcliffe Hospital (Oxford, UK), 72,297 traces from 19,506 women were analyzed using an algorithm that identifies HF sinusoidal rhythms. The case records were reviewed. There were 15 (0.21/1000) traces from 8 (0.41/1000) women with an HF sinusoidal rhythm. In 5 of 8 women (62.5%), this pattern was associated with fetal anemia (hemoglobin < 10.0 g/dL). Their FHR patterns were distinguished from those of the other nonanemic fetuses by significantly lower long-term variability. An antepartum HF sinusoidal rhythm is rare but associated with fetal anemia, particularly if it is combined with reduced long-term variability without episodes of high FHR variability within 60 minutes. The automated system can alert inexperienced staff, who supervise FHR monitoring, by an online warning.

ECG and Heart Rate Variability Changes in Preterm and Near-Term Fetal Lamb Following LPS Exposure

The aim of this study is to evaluate the myocardial response in the preterm and near-term fetal lamb with infection. Chronically instrumented fetal lambs were exposed to lipopolysaccharide (LPS), and the fetal electrocardiogram (FECG) ST waveform was examined using STAN. Fetal heart rate variability (FHRV) was automatically analyzed by adapting a polynomial function to the RR sequence in the FECG. Preterm fetuses exposed to >90 ng/kg LPS died within 8 hours of LPS administration, a response not seen in near-term fetuses. In both surviving and nonsurviving preterm fetuses, cardiovascular responses were characterized by decreased arterial pressure, negative T waves, and tachycardia accompanied by an increase in FHRV. Similar changes were not observed in the near-term fetuses after LPS. The study shows that preterm lambs are more sensitive to LPS in terms of myocardial/cardiovascular response than the more mature fetuses are. High FHRV and negative ST waveform seem to characterize the LPS-induced stress response in preterm fetuses.

A comparison of fetal behaviour in term fetuses exposed to anticonvulsant medication with unexposed controls

Objective To compare behaviour in term fetuses exposed to anticonvulsants with unexposed controls. Design An observational study. Setting Pregnancy Assessment Centre, University Hospital, Nottingham, UK. Sample Seventeen fetuses whose mothers were taking anticonvulsants and 94 fetuses whose mothers were on no medication between 28 and 41 weeks. Methods Behaviour (fetal heart rate and activity) was recorded with the use of Doppler ultrasound. The duration of recording was 60 minutes or more in all but four recordings (minimum 49 minutes). Main outcome measures Behavioural criteria studied were: 1. the relative percentage time spent in low and high variation fetal heart rate patterns; 2. the duration and recurrence of fetal activity; 3. the number of accelerations in low and high fetal heart rate variation; and 4. the number of fetal behavioural state transitions. Results The two groups were comparable in terms of maternal age, parity, birthweight, Apgar scores and absence of neonatal problems. There was less fetal activity in the anticonvulsant group, but this was only statistically significant at 33–36 weeks in fetal heart rate pattern B (equivalent to state 2F). Conclusions This study showed that fetuses exposed to anticonvulsant medication exhibited a trend of being less active. There were no other significant differences in behaviour. The data do not support the hypothesis of substantial differences in behaviour in fetuses exposed to anticonvulsants.

Computerized analysis of acute and chronic changes in fetal heart rate variation and fetal activity in association with maternal smoking

Objective: To investigate the acute and chronic changes in fetal heart rate and fetal activity in association with maternal smoking by means of a computerized fetal behavior assessment program. Study Design: In 13 term nonsmokers and 13 term smokers, fetal behavior was analyzed for 2 consecutive periods of >60 minutes. In between these 2 periods, the smokers were allowed to smoke 1 cigarette, the nonsmokers were allowed a short break of comparable time span. Fetal heart rate variation and fetal activity were recorded by a single 1.5-MHZ ultrasound transducer. The percentage of time spent in low and high fetal heart rate variation and fetal activity were analyzed by computer before and after the short break for nonsmokers and before and after the smokers smoked the 1 cigarette. Smoking-induced changes in Doppler umbilical artery recordings were also investigated. Chronic exposure to cigarette smoke was objectively evaluated by measuring the carbon monoxide concentration in expired air in all participating women after breath holding. Results: Fetuses chronically exposed to cigarette smoke spent significantly more time in a low fetal heart rate variation pattern, while fetal activity was decreased both in high and low fetal heart rate variation periods. After maternal smoking, no acute changes were observed in fetal heart rate variation, yet a reduction in fetal activity was noted; however, this only reached statistical significance in periods of high fetal heart rate variation. No significant change in mean fetal heart rate was observed, yet a significant reduction in the frequency of accelerations was noted. Smoking caused an acute and transient increase in the mean pulsatility index in the umbilical artery. Conclusion: The computer program was able to detect changes in fetal behavioral variables in association with acute and chronic smoking. These changes may be suggestive of altered neurodevelopmental maturation possibly resulting from chronic fetal hypoxemia. This computer program offers a real possibility that analysis of fetal behavioral variables can be brought into routine clinical practice. Incorporating an analysis of these behavioral variables into smoking cessation programs may render them more successful. (Am J Obstet Gynecol 2001;185:421-6.)

A comparison of fetal behaviour in breech and cephalic presentations at term.

To evaluate fetal behaviour in breech and cephalic fetuses at term, using a computerised fetal behaviour program. An observational study. Pregnancy Assessment Centre, University Hospital, Nottingham. Twenty-six breech and 58 cephalic fetuses between 36 and 41 weeks. Behaviour (fetal heart rate and activity) was recorded with the use of Doppler ultrasound. The duration of recording was 60 minutes or more in all but four recordings (minimum 49 minutes). Behavioural criteria studied were 1. the relative percentage time spent in low and high variation fetal heart rate patterns; 2. the duration and recurrence of fetal activity; 3. the number of accelerations in low and high fetal heart rate variation; and 4. the number of fetal behavioural state transitions. Breech fetuses differed from the cephalic group in that they were lighter than the cephalic fetuses (median 3105 g vs 3400 g; P < 0.01) and were born to older mothers (median maternal age 30 years vs 28 years; P < 0.01). No significant differences were found in rates of movement, numbers of accelerations and time exhibiting low and high fetal heart rate variation. However, breech fetuses exhibited significantly more state transitions (median 5.2/h vs 3.69/h; P = 0.01). This study shows that breech fetuses are neurologically different from their cephalic counterparts in otherwise healthy pregnancies, and that subtle behavioural differences can be demonstrated in utero using this computerised method.

Cardiovascular and metabolic responses to intermittent umbilical cord occlusion in the preterm ovine fetus.

To determine the cardiovascular and metabolic responses to umbilical cord occlusion in the preterm ovine fetus and the impact of repetitive intermittent insults over a 4-day period. Repetitive umbilical cord occlusions (experimental group, n = 7; control group, n = 7) were performed daily (112-115 days' gestation, term = 147 days). Mean arterial pressure (MAP), fetal heart rate (FHR), and FHR variation were monitored, and arterial blood was sampled at predetermined intervals. During umbilical cord occlusions, arterial oxygen pressure (PaO2) (approximately 17 mmHg) and glucose (approximately 0.3) millimoles per liter (mmol/L) fell and arterial carbon dioxide pressure (approximately 8 mmHg) rose (P < .01) to a similar extent on days 1 and 4. Umbilical cord occlusion produced a rise in lactate over the course of successive umbilical cord occlusions each day, the magnitude of which tended to be reduced by day 4 (0.3 +/- 0.1 versus 0.6 +/- 0.1 mmol/L). Control hour FHR and MAP were unaltered over the 4 days, but the delta (delta) FHR to delta PaO2 ratio during umbilical cord occlusions was less on day 4 than on day 1 (6.0 +/- 0.4 versus 10.9 +/- 1.5 beats per minute/mmHg; P < .01). During occlusion hours, high FHR variation episodes, as a measure of fetal activity, were reduced (14.6 +/- 1.5 versus 4.2 +/- 1.3 min/h; P < .01), whereas the reduction in short-term (7.4 +/- 0.7 to 5.8 +/- 0.6 milliseconds; P < .05) and long-term (34.9 +/- 2.7 to 30.0 +/- 0.6 milliseconds; P < .05) FHR variation reached significance only on day 4. The increase in lactate and reduced high-FHR variation episodes over successive umbilical cord occlusions may affect fetal growth and development. Furthermore, repeated umbilical cord occlusions over several days alter the preterm FHR response to subsequent stresses, suggesting an altered chemoreflex response.

Computerised analysis of unstimulated and stimulated behaviour in fetuses with intrauterine growth restriction

Unstimulated (passive) and stimulated behaviour, in the form of fetal heart rate (FHR) and activity (FA)) was studied in 32 normal fetuses and 14 fetuses with intrauterine growth restriction (IUGR). FHR and FA were recorded using a single 1.5 MHz ultrasound transducer and analysed by computer. A 5 s vibroacoustic stimulus (VAS) (electronic artificial larynx) was used for the stimulation studies. The IUGR fetuses had significantly different patterns of both unstimulated and stimulated behaviour compared to normally grown fetuses. When unstimulated they had lower FA rates than the normally grown fetuses but this was only statistically significant at 28–31 weeks. They also spent a significantly lower proportion of time exhibiting high FHR variation at 28–31 weeks. Following VAS the IUGR fetuses had lower FA responses at all gestations and lower FHR responses from 32 weeks, though only the differences in FA response at 28–31 weeks were statistically significant. Of the 14 fetuses with IUGR, all but one exhibited passive behaviour (ERR and/or FA) that was outside the 10–90th range, for normally grown fetuses, whilst 6 of the 14 had responses to VAS that were within the normal range. We do not feel that computerised assessment of stimulated behaviour in preterm IUGR fetuses confers any advantage over passive observations.

The effect of uterine contractions on intrapartum fetal heart rate analyzed by a computerized system

Objective: Our goal was to assess the effect of uterine activity on fetal heart rate indexes during the active phase of labor with a computerized fetal heart rate monitoring system. Study Design: Twenty-six healthy women were studied in active labor without analgesia. Fetal heart rate was analyzed by a computerized system (Sonicaid, System 8000), providing a numeric analysis of the fetal heart rate indexes. Montevideo and Alexandria units were used for quantitative assessment of contractions. Results: A significant correlation was found between Montevideo units and short-term variation ( r = –0.62, p < 0.001), episodes of high ( r = –0.48, p < 0.01) and low ( r = 0.58, p < 0.01) fetal heart rate variation, and frequency of large accelerations ( r = –0.49, p < 0.01). A significant correlation was also found between Alexandria units and short-term variation ( r = –0.645, p < 0.001), episodes of high fetal heart rate variation ( r = –0.58, p < 0.01), and frequency of large accelerations ( r = –0.49, p < 0.01). Conclusions: In active labor fetal heart rate variability is significantly affected by the intensity and duration of contractions. (Am J Obstet Gynecol 1998;178:436-40.)

Ethnicity and fetal heart rate variation

Objective: To determine the effect of ethnicity on fetal heart rate (FHR) variation. Methods: A prospective study was conducted of 27 consecutive black women (of African or Caribbean ethnic origin) and 79 consecutive white women (of European ethnic origin) volunteers attending the antenatal clinic, with uncomplicated singleton pregnancies of at least 34 completed weeks' gestation. The participants had cardiotocography performed with an FHR monitor connected to a Sonicaid System 8002 computer. We studied the mean FHR, long-term FHR variation, short-term FHR variation, the number of accelerations, and the reactivity of the FHR. Results: The long-term FHR variation in centiles corrected for gestational age, the duration in minutes of episodes of high FHR variation, the long-term FHR variation in beats per minute during episode of high FHR variation, and the number of accelerations were significantly reduced in fetuses of black women compared with those in fetuses of white women ( P = .007, P = .005, P = .009, and P = .006, respectively, Mann-Whitney U test). The fetuses of black women had a significantly higher proportion of nonreactive traces ( P = .009, Fisher exact test). However, there was no significant difference in the short-term FHR variation between the two groups ( P = .101). Conclusion: There is an ethnic difference in FHR variation, with significantly reduced long-term variation in black fetuses.

Computerised analysis of behaviour in normal and growth-retarded fetuses

Fetal behaviour [fetal heart rate (FHR) variation and movements (FA)] was studied in 27 normally grown fetuses and in 18 fetuses with intrauterine growth restriction (IUGR). FHR and FA were recorded using a single 1.5 MHz ultrasound transducer and analyzed by computer. The IUGR fetuses had significantly lower FA rates than the normally grown fetuses at all gestation times. They also spent a significantly lower proportion of time exhibiting high FHR variation at 28–31 weeks. Only two of the eighteen IUGR fetuses had abnormal biophysical profile scores (BPS) at the time of recording and yet all but one of them had either FHR or FA patterns that were outside the 10–90th centile range for the normally grown fetuses, suggesting that FHR and FA abnormalities predated BPS changes. More of the IUGR fetuses had abnormalities of FA than FHR. Finally, within the IUGR fetuses, those with small head circumferences (less than 3rd centile) had lower FA rates during periods of both low and high FHR variation, though this was only statistically significant for periods of low FHR variation ( P<0.05). This preliminary study offers the possibility that such objective evaluation of fetal behaviour could be used in a clinical setting and provide a more sensitive method of fetal assessment than the BPS.

Noninvasive monitoring of fetal heart rate during the last ten days of gestation in sows

SUMMARY Objective To develop and evaluate a noninvasive technique for monitoring and analyzing porcine fetal heart rate (FHR) during late gestation. Animals 8 fetuses of 8 pluriparous sows in late gestation. Procedure With the sow positioned in lateral recumbency, the most caudal fetus was identified, using real time ultrasonography, and its heart rate was recorded for 60 minutes by use of Doppler cardiography. The same fetus was identified and monitored repeatedly during the last 10 days of gestation, excluding the 24 hours before delivery. Visual inspection and computerized analysis of the recordings were performed. Results 66 one-hour recordings were obtained from 8 fetuses, 1 in each of 8 sows. Mean signal loss was 37.5%. Episodes of low FHR and low FHR variation (FHR pattern A) alternated with episodes of high FHR and high FHR variation (FHR pattern B). This cyclic alternation between 2 distinct FHR patterns was observed in 46 of 66 (69.7%) recordings, and suggests the presence of different behavioral states in fetal pigs. Basal FHR decreased toward parturition in 7 fetuses, but increased in 1 fetus with abdominal ascites. Basal FHR and long-term FHR variation were negatively correlated (r[S) = −0.73; P &lt; 0.001). Conclusion Noninvasive monitoring of FHR is possible and feasible during late gestation in pigs. This method permits longitudinal studies under pathophysiologic conditions and the evaluation of the effects of endogenous and exogenous influences on porcine FHR. (Am J Vet Res 1997;58:1285–1290)

Improvements in computerized fetal heart rate analysis antepartum.

The continued development of a computerised system for measuring the pattern of the antepartum fetal heart rate (FHR) is described. Previous work had established that measurement of FHR variation objectively detects chronic fetal hypoxaemia and the onset of metabolic acidaemia antepartum. The normal centiles were calculated for the amplitude of long-term FHR variation, in episodes of high and low variation, week by week from 24-42 weeks gestation. Reference to these (automatically by the computer) improved discrimination between normal and questionable records in 38% of records, with a small saving of time. Two types of sinusoidal rhythm were described (slow, 1 in 2-5 minutes, incidence 0.16% of subjects; and faster, 2-5 per minute, incidence 0.025%) with methods for their detection. Both may be of sufficient amplitude to induce an episode of high FHR variation. The different effects of maternal steroid (betamethasone or dexamethasone) administration of FHR variation were compared, and the clinical consequences considered. The frequency distribution of basal FHR in normal and abnormal records was measured, and the effects on basal FHR outside the normal range (120-160 bpm) on FHR variation described. Adjustment of the FHR baseline was undertaken when, exceptionally, large abrupt changes in heart rate occurred during a record. The duration and frequency of FHR record acquisition in clinical practice were reviewed, and new policies recommended. With adequate safeguards, measurement by a computer offers reliable objective information from which fetal health may be assessed, more objectively and accurately than by visual inspection.

Heart rate variation during fetal behavioural states 1 and 2.

Fetal heart rate (FHR) variation was numerically assessed in relation to behavioural states in 34 normal near term fetuses, in order to study the normal ranges of FHR variation during state 1F and 2F and to determine possible factors influencing variation in these states. In all individuals 2-h recordings were made of fetal heart rate, and body and eye movements. FHR variation was quantified using the Sonicaid System 8000. During both 1F and 2F there was a large range in variation, with a wide overlap in variation between both states (mean 1-min range in pulse intervals 16-53 ms and 36-97 ms, respectively). In all fetuses variation was higher during 2F than during 1F. The large ranges in variation were mainly caused by differences in basal heart rate and the correlation coefficients between rate (beats/min) and variation were -0.68 and -0.49 for 1F and 2F, respectively. Other reasons for a relatively high FHR variation during 1F included 'pseudo' sinusoidal patterns related to fetal sucking or mouth movements and relatively flat periods sporadically interrupted by an acceleration. With the System 8000, periods of low and high variation are identified using fixed criteria. Because of the large overlap in variation between both states, these episodes poorly correlated with the underlying behavioural states. Objective identification of the heart rate patterns during states 1F and 2F requires incorporation of heart rate itself in the analysis. As yet, 'global' visual identification of heart rate patterns is superior to computer analysis in identifying the underlying fetal behavioural states.

Vibro-acoustic stimulation does not alter the duration of high and low fetal heart rate variability episodes.

To study the effect of vibro-acoustic stimulation on high and low fetal heart rate (FHR) variability episodes. Prospective control study, in 21 high risk pregnancies between 32 to 39 weeks gestation. FHR pattern was recorded with cardiotocograph (CTG). After 5 min low FHR variability a vibro-acoustic stimulator was activated in contact with or above the maternal abdomen (sham) on a random basis on two consecutive days, and CTG was continued to obtain a complete high and low FHR variability cycle. Complete high and low FHR variability cycles were obtained in 12 patients with mean recording time of 129.5 minutes (range 69-185 min). The mean baseline FHR increased by 32.5 +/- 9.4 bpm after contact vibro-acoustic stimulation, but remained unchanged after sham stimulation. Mean duration of high FHR variability was 56.6 +/- 32.9 min and 47.3 +/- 23.7 min, respectively, and mean duration of the consecutive low FHR variability episode was similar after contact and sham stimulation. The complete cycles were 71.1 +/- 34.7 min and 66.2 +/- 21.2 min, respectively. Vibro-acoustic stimulation induced an abrupt change from low to high FHR variability, but the complete cycle of high and low FHR variability was not altered, when compared with the corresponding cycle following sham stimulation on the same fetus.

Fetal heart rate response to vibroacoustic stimulation during low and high heart rate variability episodes in late pregnancy

In 52 women in late pregnancy, the mean durations of transient fetal tachycardia after vibroacoustic stimulation during low fetal heart rate variability (4.8 minutes) and high fetal heart rate variability (6.3 minutes) were similar. The fetal heart rate continued with high variability in all cases, suggesting that the fetus did not return to its prestimulation state after vibroacoustic stimulation during quiescence. In 10 women, the duration of high variability after vibroacoustic stimulation during low fetal heart rate variability was significantly shorter (mean, 22 minutes) than the preceding (mean, 36 minutes) or subsequent (mean, 43 minutes) high-variability components of complete rest activity cycles. In another 10 women, the duration of high variability after vibroacoustic stimulation during high fetal heart rate variability was similar to preceding and subsequent high-variability episodes. In these 20 women, the next complete rest-activity cycle after vibroacoustic stimulation was not different in duration to the complete cycle recorded on the previous day.

Analysis of fetal heart rate on-line at 32 weeks gestation.

Antenatal fetal heart rate (FHR) patterns were screened in 634 women with singleton pregnancies at 32 weeks gestation using a microprocessor on-line. The duration of the record was adjusted according to its character, varying from 10 min with high FHR variation (39% of records) to 45 min with low variation (4.7%). The average duration was 16.7 min. Of the 30 fetuses with the lowest FHR variation (less than 5th centile), 19 (63%) had a normal outcome. Of the 11 with an abnormal outcome five were born greater than or equal to 38 weeks; six were born by caesarean section at 32-34 weeks, resulting in an increased incidence in the group. Analysis of the numbers of accelerations, of decelerations, of episodes of high FHR variation or of fetal movements did not improve long-term prediction. It was concluded first, that antenatal FHR monitoring for up to 45 min at 32 weeks gestation had no long-term predictive value; and second, that 3% of our obstetric population have unreactive FHR traces at this age, with a normal outcome. This does not imply that consecutive antenatal records on the same high-risk patient at short intervals are not valuable clinically.

Micturition and the heart period cycle in the human fetus.

SummaryCampbell et al (1973) suggested that from 32 weeks gestation there was a cyclic filling and emptying of the fetal bladder, with a mean cycle length of 110 minutes. In the present study it was found that emptying of the bladder was associated with cyclic changes in fetal heart rate variation. In 95 per cent of the observations voiding occurred within 30 minutes after a change from a low to a high fetal heart rate variation episode. The possible relation of this association to fetal behavioural states is discussed.