Ontogeny of behavioral patterns in relation to the concurrent development of central nervous system function, focusing on REM sleep, NREM sleep and waking states in the human fetus

Behavior is considered a one to one match between the manifestation of a particular individual motor activity (movement) and its correlated brain function. Each motor activity can be seen to run on its own developmental course with advance in gestation, while various movements also develop in concurrence with one another during intrauterine life, gradually integrating into complex and accommodated movements. I emphasized the present study, under real-time ultrasound observation, for investigating whether or not three states: REM (rapid eye movement) sleep, NREM (non-rapid eye movement) sleep and the waking state actually exist in utero, and if so, when the development of these states begins. 1. Examined for 30-40 minutes were 21 fetuses, including 10 from 33 to 36 weeks of gestation and 11 from 37 to 41 weeks of gestation. As parameters, the duration of each eye movement unit and the cumulative duration of this movement, from the shortest to a given duration, per individual case, were observed. A scattergram of cumulative duration vs, given duration obtained from all cases, for each age-group, were analyzed using "piecewise linear regression". Critical points were noted, with statistical significance, at 0.62 second for the earlier group and at 0.76 second for the later group. These findings reveal two different types of eye movement: rapid and slow eye movements. The fact that the rapid eye movement coexists with the slow eye movement during REM period indicates that REM sleep exists in utero at the latest at 33 weeks of gestation. 2. Observed for 60 minutes were 26 fetuses from 28 to 41 weeks of gestation. Regular mouthing movement every 300 to 600 msec concurred significantly only with the NREM period from 35 weeks of gestation onwards. Random mouthing movements were observed predominantly during REM sleep and were unrelated to the advance in gestational age. This concurrence between the NREM period and regular mouthing indicates the existence of NREM sleep in utero at this age of gestation. 3. To evaluate whether the waking state is present, 10 fetuses at 36 weeks or more of gestation were examined for a concurrence between miosis/mydriasis and the REM/NREM periods. Using pupil diameter as a parameter, miosis and mydriasis were distinguished from each other, statistically, by means of "least median of squares regression". Accordingly, the NREM period was occupied only by miosis (41.0% of total observation period), while the REM period was divided into two conditions: 52.6% with miosis and 6.4% with mydriasis.(ABSTRACT TRUNCATED AT 400 WORDS)     

Analysis of newborns' health status in twin pregnancies according to the duration of pregnancy and its delivery based on the materials of Reproduction and Obstetrics Clinic in 1995-1999

On the ground of the analysis of 79 twin pregnancies, the valuation of newborns' condition in Apgar's scale, according to the delivery means, has been executed. The lack of differences between the mean values of the scale has been ascertained. There was no indication of any difference between the condition of the twin I and II. Furthermore, there has been executed a detailed comparative analysis of the newborns' condition in the four periods of the pregnancy duration: 23-27, 28-32, 33-37 and 38-42 weeks of gestation. It has been ascertained that the newborns delivered through the abdominal delivery were in better condition than those born in the spontaneous delivery, in the 28-32 weeks of gestation period. The use of rather intraspinal rather than general anesthesia in the 33-37 weeks period gave better results by improving the newborns' condition. Moreover, there has been stated a similar condition of the newborns delivered through either spontaneous or abdominal delivery with intraspinal anesthesia in the periods of 33-37 and 38-42 weeks of gestation.     

Relationship between the duration of fetal breathing movements and gestational age and the development of the central nervous system at 25-32 weeks of gestation in normal pregnancy

In 15 pregnant women with normal pregnancy at 25-32 weeks of gestation, fetal breathing movements (FBM), fetal body movements and fetal heart rate were continuously and simultaneously recorded over a total period of 180 min. The frequency of successive FBM with a duration less than 10 s (apnea period greater than 3 s) showed a significant decrease (p less than 0.01), while the frequency of successive FBM with a duration greater than or equal to 30 s showed a significant increase from 25 to 32 weeks of gestation (p less than 0.001). Strong positive correlations were also demonstrated between the frequency of FBM with a duration of greater than or equal to 30 s and the number of fetal heart rate accelerations per hour, acceleration/fetal body movement ratio, and the value of fetal heart rate long-term variability. These results suggest that the length of the duration of successive FBM represents a useful parameter for the analysis of fetal respiratory patterns, and that a prolongation of the duration of successive FBM of an individual fetus is related to the functional development of the central nervous system.     

Number and gestational age of prior preterm births does not modify the predictive value of a short cervix

OBJECTIVE: This study was undertaken to determine whether the number and gestational age of prior preterm deliveries modifies the significance of endovaginal sonographic cervical length less than 25 mm for the prediction of recurrent preterm birth less than 35 weeks' gestation. STUDY DESIGN: Secondary analysis of a multicenter, blinded, observational study. Endovaginal ultrasonographic examinations were scheduled at 2-week intervals between 16 and 23 weeks' gestation in singleton pregnancies of 181 gravid women with at least 1 prior spontaneous preterm birth between 16 and 32 weeks' gestation. RESULTS: The earliest prior preterm birth occurred before 23 weeks in 61 women and at 23.0 to 31 weeks in 115; 5 had missing gestational age data. Cervical length was not different between these 2 groups both at the initial scan (median 38 vs 37 mm, P=.54) and considering the shortest ever observed cervical length over the entire study period (median 30 vs 30 mm, P=.97). Cervical length less than 25 mm was associated with spontaneous preterm birth less than 35 weeks for both groups (positive predictive value 80% vs 71%, P>.99). There were 134 women with 1 prior preterm delivery (74%) and 47 with 2 or more. Cervical lengths were not different between these 2 groups at the initial scan (median 36.5 vs 37 mm, P=.52) or over the entire study period (median 30 vs 32 mm, P=.31). The positive predictive value of cervical length less than 25 mm for subsequent spontaneous premature birth was not significantly higher in gravid women with multiple prior preterm births (100% vs 73%, P>.99). CONCLUSION: Neither the number nor the gestational age of prior preterm births modify the predictive value of a cervical length less than 25 mm at 16 to 19 weeks for recurrent spontaneous preterm birth.     

Analysis of fetal breathing movements at 30-38 weeks of gestation

AIMS: This study reports the changes in patterns of fetal breathing movements recorded with a photogrammetric method in three successive periods of gestation. METHODS: Respiratory movements were studied in fetuses of 28 healthy women with uncomplicated pregnancies of 30-38 weeks of gestation. Women were divided into three groups according to gestational age of the fetus: 30-32 weeks, 7 fetuses; 33-36 weeks, 9 fetuses; and 37-38 weeks, 12 fetuses. Sonographic images of the fetuses were recorded on videotape, digitized (1 image per 0.12 s) and analyzed with specially developed software. RESULTS: The proportion of fetuses in each age group for which movements were detectable was similar in all three groups, as was the frequency of movements. Duration of a complete respiratory cycle, the inspiratory phase and the expiratory phase tended to be shorter at 33-36 weeks of gestation than in younger and older fetuses. Fetuses in the 30-32-week group had slower breathing rates than fetuses in the two older groups. CONCLUSIONS: The photogrammetric technique revealed differences in some patterns of fetal breathing movements between weeks 30-32, 33-36 and 37-38 of gestation. The data provide a sound basis for relating changes in fetal breathing movements with physiological and anatomical changes that occur as the respiratory system matures.     

Functional development of human eye movement in utero assessed quantitatively with real-time ultrasound

Functional development of eye movement in the human fetus in utero was assessed quantitatively, with real-time ultrasound. A pair of lens-derived echoes was used as a landmark to evaluate positional deviation with eye movement. The frequency of eye movement was measured either with 1-minute continuous observations or at 1-minute cross sections. Two hundred forty-five normal fetuses between 18 and 42 weeks of gestation were studied. Three critical ages, with respect to physiologic development of fetal eye movements, were evident: 22 to 25, 30 to 33, and 38 to 41 weeks. The first and the second indicate the onset of the moderate-frequency and high-frequency eye movements, thereby implying a transition, presumably to a state of so-called rapid eye movement and a rise of rapid eye movement, respectively. The third represents full maturation of the mechanisms, that is, non-rapid eye movement and rapid eye movement.     

Does the nuchal cord persist? An ultrasound and color-Doppler-based prospective study

AIM: To study the persistence of nuchal cord by ultrasound at various periods of gestation. METHODS: Ultrasound was done on 200 consecutive pregnant women and nuchal cord was documented at 18-20, 30-32 and 36-38 weeks' gestation. RESULTS: The incidence of nuchal cord was 6% at 18-20 weeks, 7.5% at 30-32 weeks, 26.5% at 36-38 weeks and 28% at birth. The persistence of nuchal cord was 8.3% from 18 to 20 to 30-32 weeks, 26.6% from 30-32 to 36-38 weeks and 84.9% from 36-38 weeks to delivery. Using the Friedman test, the change in the presence of nuchal cord was significant (P < 0.001). CONCLUSIONS: Nuchal cord keeps appearing and disappearing over time. Its     

Analysis of twin pregnancies on the ground of women hospitalized in the Department of Reproduction and Obstetrics Medical University in Wrocław in 1995-1999

The aim of this study was the general valuation of the course and the delivery means of the twin pregnancies. The research material composed of 83 from among 5540 pregnant women hospitalized in the Department of Reproduction and Obstetrics Medical University of Wroc?aw in the years 1995-1999. The mean body mass values and the condition of the newborns have been analyzed on the ground of Apgar's scale, according to the date of delivery. In the period between 23 and 42 week of pregnancy a very high correlation between fetus' body mass and a high correlation between Apgar's scale and the pregnancy's duration has been ascertained. These values have also been estimated in particular periods: 23-27, 28-32, 33-37 and 38-42 weeks of gestation. Statistical analysis didn't indicate any difference between the mean values of Apgar's scale of the newborns from the periods of 33-37 and 38-42 weeks of gestation. There was no evidence of differences either in Apgar's scale values or in the twins' I and II body masses, as well in the whole examined group as in particular periods.     

Studies on features of fetal movement and development of human fetus with use of fetal actogram

In 167 normal fetuses at 26 to 41 weeks of gestation, features of fetal movement and fetal development were investigated with use of actocardiograph in connection with a microcomputer system. The signals of fetal movement obtained by actocardiograph were stored in a floppy disc every 250 ms for 5 minutes through an AD-converter, and were analyzed every 5 minutes with the computer to reveal 3-dimensional (3-D) histograms. The 3-D histogram of fetal movement was composed of number, amplitude and interval of the signals in 11 voltage steps between 0.05 and 0.55V. The histogram clearly indicated state of fetal behavior, being either resting or active state. Fetal movement such as rolling movement, breathing movement and hiccup could be also identified with the computer analysis. In 68 normal fetuses at 14 to 41 weeks of gestation, the cross-correlation between fetal movement and fetal heart rate (FHR) were examined with the computer analysis. Finally fetal responses to acoustic and light stimulation were evaluated with use of pure-tone generator and flashlight. Acoustic stimulation was carried out in 53 normal fetuses at 28 to 41 weeks and light stimulation was performed in 116 normal fetuses at 18 to 41 weeks of gestation. The fetal responses were evaluated with actocardiogram. As a result, 1) Frequency in active state decreased and resting state increased as gestational weeks advanced, and then the frequencies of both state remained constant after 37 weeks of gestation. Duration of resting state also increased from 26 weeks to 37 weeks. These observations may suggest that fetal behavior can be established by 37 weeks of gestation. 2) Frequency in rolling movement decreased until 37 weeks of gestation, and then the movement increased during 38-41 weeks. Frequency in breathing movement increased to 33 weeks of gestation, then it remained constant. Hiccup occurred most frequently at 30-33 weeks, and it decreased thereafter. The function in fetal respiratory movement may be accomplished by 33 weeks of gestation. 3) Positive cross-correlation between fetal movement and FHR was observed as gestational weeks advanced. The correlation coefficient increased from 14 weeks up to 41 weeks. Acceleration of FHR following fetal movement eventually occurred in fetuses at 16 weeks, but the onset of acceleration delayed than normally occurred in developed fetuses. The delay was shortened in fetuses at 24 weeks and this was comparable to the delay in developed fetuses. These results suggest that the linkage of the acceleration of FHR with fetal movement is established at 24 weeks of gestation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cervical length at 23 weeks in twins in predicting spontaneous preterm delivery.

OBJECTIVE: To establish the relationship between cervical length at 23 weeks' gestation in twin pregnancies and risk of spontaneous preterm delivery. METHODS: Cervical length was measured during routine antenatal care by transvaginal sonography at 23 (range 22-24) weeks' gestation in 215 twin pregnancies. Distribution of cervical length was determined, and sensitivity and false-positive rate for spontaneous preterm delivery at or before 28, 30, 32, and 34 weeks for cutoff cervical lengths of 15, 25, 35, and 45 mm were calculated. RESULTS: Cervical length distribution was skewed toward shorter length and the median value was 38 mm. In 11.2% and 4.2% of cases, length was up to 25 mm and up to 15 mm, respectively. The spontaneous delivery rates at or before 28, 30, 32, and 34 weeks were 3.8%, 4.7%, 8.0%, and 17.5%, respectively, and were not statistically significantly related to any demographic characteristics, obstetric history, or chorionicity. Sensitivity to predict spontaneous preterm delivery was 100%, 80%, 47%, and 35% for 28, 30, 32, and 34 weeks, respectively, for cervical length up to 25 mm. The corresponding sensitivity values for cervical lengths up to 15 mm were 50%, 40%, 24%, and 11%. The rate of spontaneous delivery at or before 32 weeks increased exponentially with decreasing cervical length at 23 weeks, from 2.9% at or greater than 46 mm, to 4.3% at 36-45 mm, 6.7% at 26-35 mm, 31% at 16-25 mm, and 66% at 15 mm or less. CONCLUSION: Measurement of cervical length in twin pregnancies predicted risk of spontaneous early preterm delivery.     

A fetal response to chorioamnionitis is associated with early survival after preterm birth

OBJECTIVE: The purpose of this study was to determine, in a large preterm cohort (20-34 completed weeks of gestation), the incidence of histologic chorioamnionitis and the incidence of a histologic fetal response to chorioamnionitis (umbilical vasculitis with or without funisitis) in neonatal survivors (to 28 days) and perinatal deaths. STUDY DESIGN: Placental histopathology was reviewed (n=3928 reports). In a subset of this cohort (n=2076 reports), evidence of a histologic fetal response was compared in neonatal survivors and perinatal deaths. RESULTS: The incidence of histologic chorioamnionitis ranged from 66% at 20 to 24 weeks of gestation (n=261 neonates) to 16% at 34 weeks (n=770 neonates). The overall incidence was 31% (n=3928 neonates). At 25 to 29 weeks of gestation, neonatal survivors had a higher incidence of histologic chorioamnionitis (P=.02; 95% CI, 1.02-1.21). In addition, neonatal survivors had a higher incidence of a histologic fetal response to chorioamnionitis at 25 to 29 weeks of gestation (P=.01; 95%CI, 0.33-0.86) and 30 to 34 weeks of gestation (P=.02; 95%CI, 0.18-0.85). CONCLUSION: Histologic chorioamnionitis is inversely related to gestational age. Both histologic chorioamnionitis and a histologic fetal response to chorioamnionitis were observed to be more common in preterm survivors of the neonatal period.     

Hemorheological studies on platelet counts and size in normal pregnancy and pregnancies with preeclampsia and intrauterine growth retardation

It has been reported that preeclampsia and pregnancy resulting in intrauterine growth retardation (IUGR) are associated with high hematocrits. The relations between hematocrits (Ht) and platelet volumes in normal and abnormal pregnancies were investigated to clarify a hemorheological effect on formation of microthrombus. 1) In normal pregnancy, Ht was decreased from 12-19 weeks gestation and reached its lowest level at 28-31 weeks gestation. The mean platelet volume (MPV) was decreased from 20 to 31 weeks gestation but markedly increased from 38 to 41 weeks gestation. The platelet count (Pl) remained unchanged during pregnancy. 2) In severe type of preeclampsia, at 28-37 weeks gestation Ht and MPV were markedly increased and Pl was markedly decreased at 38-41 weeks gestation as compared with normal pregnancies. 3) Mothers who delivered IUGR had a much higher level of Ht at 28-35 weeks gestation and MPV level from 38 weeks gestation than in normal mothers. As the volume of young platelets is large, increased MPV is suggestive of the occurrence of platelet consumption. From these results, it was suggested that microcirculatory disturbances such as higher blood viscosity due to hemoconcentration and microthrombus formation were related to the onset of preeclampsia or IUGR.     

Low incidence of positive amnionic fluid cultures in preterm labor at 27-32 weeks in the absence of clinical evidence of chorioamnionitis

In order to determine the utility of amniocentesis for detecting subclinical chorioamnionitis in asymptomatic afebrile women in preterm labor with intact membranes, we enrolled 47 women between 27-32 weeks' gestation in a prospective study. After enrollment, 38 women fulfilled all clinical and laboratory criteria for the study; nine women were excluded because they had a leukocyte count exceeding 15,000/microL. None of the 38 asymptomatic afebrile women had a positive culture from the amnionic fluid for bacteria, fungi, Mycoplasma hominis, Ureaplasma urealyticum, Chlamydia trachomatis, or any viruses. Sepsis was not proved in any of the 38 infants delivered to these patients. There was a clear relationship between histologic evidence of chorioamnionitis and failure of tocolytic therapy. Fetal lung profiles were mature in 29% of the amnionic fluid samples from 30-32 weeks' gestation, but in none of the amnionic fluid samples before 30 weeks. Amniocentesis does not seem useful to detect chorioamnionitis in asymptomatic afebrile women with preterm labor and intact membranes at 27-32 weeks' gestation, and should be reserved for those cases in which information about fetal lung maturity would be helpful.     

Combination therapy for fetal supraventricular tachycardia with flecainide and digoxin

Persistent fetal supraventricular tachycardia (SVT) with more than 210 bpm frequently leads to congestive heart failure. We report on a case with SVT and congestive heart failure that converted into sinus rhythm within 19 days of therapy with flecainide and beta-acetyldigoxin. A 32-year-old II gravida I para (25 + 1 weeks of gestation) presented with fetal SVT of 267 bpm. A non-immunologic hydrops fetalis was diagnosed by ultrasound showing ascites, pleural and pericardial effusion and tricuspid regurgitation. Within 19 days of combination therapy with flecainide and digoxin, cardioversion was achieved. After 36 days of therapy no more signs of cardiac failure could be detected. A healthy boy was born at 38 + 6 weeks of gestation. Although cardioversion is expected after 72 h of therapy according to the literature, this fetus converted into sinus rhythm on day 19 of therapy. This indicates that patients should not be considered resistant to treatment within the first 3 - 4 days.     

Contribution of elective delivery to severe respiratory distress at term

We sought to determine the contribution of elective delivery to severe respiratory distress syndrome (RDS) on a weekly basis from 37-40 weeks' gestation. Chart reviews confirmed gestational age, delivery reason, and primary diagnosis of all inborn neonates with RDS requiring mechanical ventilation delivered at 37 0/7-40 6/7 weeks' gestation from 1/1/90-12/31/99. Exclusion criteria were sepsis, pneumonia, meconium aspiration, asphyxia, pulmonary hemorrhage, hydrops, chromosomal abnormality, or congenital malformations affecting respiration. Thirty-five thousand and thirty-one deliveries occurred from 37 0/7-40 6/7 weeks; 18 (0.05%) had RDS requiring mechanical ventilation. Nine infants delivered at 37 0/7-37 6/7 weeks, (OR for RDS = 38.5; 95% CI = 8.3, 178.3), seven delivered at 38 0/7-38 6/7 weeks, (OR for RDS = 13.3; 95% CI = 2.8, 64.0), and two delivered at 39 0/7-40 6/7 weeks. Six of 18 infants were electively delivered without documented lung maturity. Infants born at 37 0/7-38 6/7 weeks are at significantly increased risk for severe RDS. One third of RDS cases were potentially avoidable.     

Survival and short-term morbidity of the premature neonate

Obstetric decisions regarding premature (23 to 32 weeks' gestation) infants must be based on gestational age. However, most reports of the survival of premature infants are based on birth weight. The present report relates the perinatal survival and morbidity of 105 newborns to the obstetric gestational dating criteria between 23 and 32 weeks' gestation. Gestational age was determined from at least four obstetric criteria including the first day of the last menstrual period, early pelvic examination, the earliest auscultation of fetal heart tones with a fetoscope, fundal height measurements in centimeters between 20 and 30 weeks' gestation, and sonographic gestational age measurements. At 23 to 26 weeks' gestational age, nine (39%) of 23 neonates survived. Five of nine survivors had moderate to severe intracranial hemorrhage, three had moderate to severe bronchopulmonary dysplasia, and three had moderate to severe retrolental fibroplasia. At 27 to 29 weeks' gestational age, 25 (93%) of 27 neonates survived. Of the 25 survivors, three had moderate to severe intracranial hemorrhage, one had moderate to severe bronchopulmonary dysplasia, and one had severe retrolental fibroplasia. At 30 to 32 weeks' gestational age, 52 (95%) of 55 neonates survived. Three of the 52 (6%) survivors had serious neonatal morbidity consisting of moderate to severe intracranial hemorrhage (three neonates) and moderate to severe bronchopulmonary dysplasia (one neonate). Thus, ten of 34 (29%) survivors between gestational ages of 24 to 29 weeks had a serious morbidity versus only three of 52 (6%) survivors between 30 to 32 weeks' gestation (P less than .01).     

A randomized trial of ritodrine tocolysis versus expectant management in patients with premature rupture of membranes at 25 to 30 weeks of gestation

Expectant management was compared with similar management plus ritodrine tocolysis in a randomized controlled trial in patients with premature rupture of membranes at 25 to 30 weeks of gestation. In the tocolysis group intravenously administered ritodrine was instituted at the onset of labor and then changed to the oral form if successful. Tocolysis was discontinued or not instituted after 31 weeks of gestation. Seventy-nine patients were randomized over a 4-year period, 39 in the tocolysis group and 40 in the expectant group. Twenty-three patients in the tocolysis group actually received ritodrine. No difference between the two groups was demonstrated in the interval between premature rupture of membranes and delivery or in reaching 32 weeks of gestation. No statistical difference was seen in maternal morbidity. Birth weights and gestational ages at delivery were similar between the two groups as were the incidences of neonatal morbidities caused by prematurity and infection and in the duration of neonatal hospital stays. Despite being conducted in those gestational ages in which prolongation of pregnancy might be expected to be of most benefit, no difference could be demonstrated with the addition of tocolytic therapy over expectant management alone.     

Evaluation of fetal development and well-being with the ultrasonic Doppler fetal actocardiograph

Fetal development and well-being were investigated during pregnancy with respect to the relation between fetal movement (FM) and fetal heart rate (FHR) in 192 normal and 43 high-risk fetuses in the antepartum period utilizing ultrasonic Doppler fetal actocardiograph that enabled the simultaneous and continuous recording of FM and FHR by single ultrasonic probe. The analysis of simultaneously obtained records of FHR and the movements of fetal trunk and legs revealed that gross fetal trunk movement was mainly related with FHR acceleration. The number of FM signal bursts, which was accompanied by fetal trunk rotating movements, showed a peak at 30-31 weeks of gestation and decreased in the other stage of pregnancy. The synchronization rate of FM signal bursts to transient FHR rises increased with gestational age, and the amplitude and inclination of the rise accompanied by bursts increased linear from the 24th to the 38th week of gestation. Fetuses of high-risk pregnancy produced on antepartum actocardiogram with low FM and FHR values. The changes were particularly remarkable in the cases of intrauterine growth retardation and/or gestosis.     

Evaluation of a non-stress test by automated FHR (fetal heart rate) analysis

The changes in 5 parameters in 1080 5 minute periods obtained by automated FHR analysis were evaluated in 140 normal and premature labor patients at 26 to 41 weeks of gestation. The FHR-baseline level was between 140.29 +/- 5.04 and 146.90 +/- 6.94 bpm and showed no significant change between 29 and 31 weeks, but then gradually declined to 134.55 +/- 15.74 bpm by the 41st week. FHR-baseline variability (LTV) showed no significant change in the period between 26 and 32 weeks, and increased to 12.82 +/- 3.16 bpm by the 41st week from 9.96 +/- 3.78 bpm in the 33rd week. Variability in a minute was 4.09 +/- 1.03 at 28 weeks, then increased to 5.63 +/- 0.81 by the 41st week. Variability of which the amplitude was 5 bpm or more in 5 minutes showed no change from the 26th to the 41st week. FHR acceleration in 20 minutes was 1.714 +/- 1.204 at 26 weeks, then increased to 4.357 +/- 2.805 by the 40th week, and the mean values were always more than 2 after 30 weeks.     

Maternal perception of fetal movements: the optimal duration of a recording period

A regular count of perceived fetal movements by the mother has been proposed as a screening method for the early recognition of fetal distress. Absence or a strongly decreased number of fetal movements during a particular period is considered as a sign of fetal distress. In the study presented, the optimal duration of a recording period for the maternal perception of fetal movements was examined. 186 pregnant patients at gestational ages of 32 and 38 weeks were asked to mark each perceived fetal movement on a time axis for two continuous hours. From these patients an 'optimal' group of 143 pregnancies was selected to constitute the study group. A window technique was applied to the 2 h recordings, searching for periods in which 0, 1 or 2 fetal movements were noted. 23% of the recordings at 32 weeks and 14% at 38 weeks showed absence of fetal movements for at least 30 min. At both 32 weeks and 38 weeks there was absence of fetal movements for more than 1 h in only 1.5% of the recordings. The findings are in agreement with the fetal behavioural state concept. A recording time of 1 h exceeds the normal duration of a fetal quiet-sleep state and minimizes the risk of unjustified suspicion of fetal distress.