Human fetal breathing movements and gross fetal body movements at weeks 34 to 35 of gestation

Human fetal breathing movements in utero at 34 to 35 weeks' gestational age were measured using a real-time ultrasonic scanner. Fetal breathing movements were episodic and occurred 31.8 per cent of the time. Aanalysis of continuous recordings in 10 fetuses from 09:00 to 17:00 hours demonstrated that the percentage of time spent breathing per hour was greater in the afternoon than in the morning. The number of gross fetal body movements was also greater in the afternoon than in the morning. The percentage of time spent breathing was significantly greater during the hour following the noon meal than during the hour preceding the noon meal. It was concluded that real-time ultrasonic scanning permits identification of fetal breathing movements and that between 09:00 and 17:00 hours the character of these movements is related to the time of the day and to the ingestion of food by the mother.     

Relation between fetal heart rate accelerations, fetal movements, and fetal breathing movements

The presence of fetal heart rate (FHR) accelerations is considered a sign of fetal well-being. Fetal body and breathing movements, as visualized by real-time ultrasound, were correlated to FHR accelerations in 16 high-risk pregnancies. The association between FHR accelerations (greater than 15 beats/min lasting 15 sec or more) and the different fetal behavioral states is described.     

The relationship between movements and accelerations in fetal heart rate at twenty-four to thirty-two weeks' gestation

The purpose of this study was to establish the relationship between fetal heart rate accelerations and fetal body movements in fetuses at 24 to 32 weeks' gestation. The results suggest that body movements in younger fetuses do not occur with accelerations that are readily recognizable (i.e., less than 15 bpm), but as fetuses get older, the interaction between body movements and fetal heart rate becomes more evident and accelerations become more recognizable (i.e., greater than or equal to 15 bpm). The data presented suggest that there is a maturational aspect to the relationship between fetal heart rate and fetal body movements as fetuses increase in gestational age from 24 to 32 weeks. The conclusion, therefore, is that the nonstress test, as presently defined for older fetuses, is not valid for gestations below 32 weeks, and new criteria must be established.     

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.     

Fetal heart rate patterns at 20 to 24 weeks gestation as recorded by fetal electrocardiography

Abstract

Introduction: With advancing technology it has become possible to accurately record and assess fetal heart rate (FHR) patterns from gestations as early as 20 weeks. The aim of our study was to describe early patterns of FHR, as recorded by transabdominal fetal electrocardiogram according to the Dawes–Redman criteria. Accordingly, short-term variability, basal heart rate, accelerations and decelerations were quantified at 20–24 weeks gestation among women with uncomplicated pregnancies.

Methods: This study was conducted in a subset of participants enrolled in a large prospective pregnancy cohort study. Our final data set consisted of 281 recordings of women with good perinatal outcomes who had undergone fetal electrocardiographic assessment as part of the Safe Passage Study.

Results: The success rate of the recordings was 95.4%. The mean frequency of small and large accelerations was 0.5 and 0.1 per 10?min, respectively and that of small and large decelerations 0.3 and 0.008 per 10?min, respectively. The mean and basal heart rates were both equal to 148.0 bpm at a median gestation of 161 days. The mean short term variation was 6.2 (SD 1.4) ms and mean minute range 35.1 (SD 7.1) ms.

Conclusion: The 20–24-week fetus demonstrates FHR patterns with more accelerations and decelerations, as well as higher baseline variability than was anticipated. Information from this study provides an important foundation for further, more detailed, studies of early FHR patterns.     

The relation between fetal heart rate accelerations and fetal movements

Fetal heart rate (FHR) accelerations associated with fetal movements is considered a sign of fetal well-being. Fetal movements as felt by the pregnant woman and visualized by real-time ultrasonography were correlated to FHR accelerations in 52 normal and high-risk pregnant women. All fetal movements felt by the mother or seen in the real-time ultrasonography were associated with large FHR accelerations (more than 15 beats per minute lasting 15 seconds or more) or small accelerations (fewer than 15 beats per minute). The large accelerations were associated with 78.6% of fetal movements felt by the mother and 99.6% of fetal movements seen by real-time ultrasonography. The small accelerations were associated with 52.9% of fetal movements felt by the mother and 82.4% of fetal movements seen by ultrasonography. Mothers felt 75.7% of fetal movements seen by real-time ultrasonography. It was concluded that fetal movements could be verified by existence of large accelerations on the FHR tracing.     

Computerised antenatal fetal heart rate recordings between 24 and 28 weeks of gestation

Objective To assess computerised fetal heart rate recordings between 24 and 28 weeks of gestation for gestation related differences.
Design Prospective, cross sectional observational study.
Setting Liverpool Women's Hospital.
Population 112 women: 28 at 27 weeks, 30 at 26 weeks, 27 at 25 weeks and 27 at 24 weeks of gestation, respectively.
Methods Fetal heart recordings of 60 minutes duration were performed once in each pregnancy using the System 8000 fetal heart rate programme (System 8000, Oxford Sonicaid Ltd, Chichester, UK). For each gestational age, records were analysed for short term variation, basal heart rate, accelerations and time spent in high episodes.
Results The mean short term variation increased with gestation (   P =0.05  ). No record had a short term variation <4 msecs. There was no relationship between heart rate and increasing gestation. The mean number of accelerations per record increased with increasing gestation (   P <0.01  ). 20% of recordings showed no accelerations  >15 bpm  . The mean duration spent in episodes of high variation increased with gestation (   P =0.05  ). 13% of recordings showed no time spent in high episodes. All fetuses had normal outcomes at delivery.
Conclusions Absence of episodes of high variation or absence of accelerations is not an abnormal finding at lower gestations. The standard threshold of 4 msecs for short term variation appears to remain valid at lower gestations. These differences should be considered when using computerised CTG analysis at early gestations.     

Effect of prolonged hypoxemia on fetal heart rate accelerations and decelerations in sheep

Experiments were conducted in 10 chronically catheterized fetal sheep to determine the effect of 24 hours of hypoxemia in the absence of progressive acidemia on fetal heart rate accelerations and decelerations. Fetal hypoxemia was produced by mechanically restricting uterine blood flow with a vascular clamp placed around the maternal common internal iliac artery. Fetal arterial oxygen tension decreased from 22.3 +/- 1.8 to 17.8 +/- 1.5 mm Hg at 2 hours and remained low for the 24-hour experimental period. Fetal pH decreased from 7.34 +/- 0.01 to 7.20 +/- 0.05 at 2 hours and returned to normal values by 12 hours. No significant change was observed in the number or characteristics of fetal heart rate accelerations or decelerations during the 24-hour control period. There was a significant increase in the number of accelerations from 48 +/- 4 to 63 +/- 4 per hour at 8 hours of hypoxemia followed by a return to control values by 12 hours. There was no significant change in the mean amplitude or duration of accelerations. There was a significant increase in the number of decelerations per hour with an associated increase in the mean amplitude but a decrease in the mean duration of decelerations during the first 16 hours of hypoxemia. We conclude that prolonged hypoxemia in fetal sheep leads to an initial increase in the number of both accelerations and decelerations in fetal heart rate followed by a return to normal patterns indistinguishable from those of the normoexemic fetus.     

The extent of fetal heart rate accelerations associated with fetal body movements in relation to the duration of fetal body movement

The temporal relations between fetal body movements and associated fetal heart rate accelerations were shown as the ratios of duration of acceleration or acceleration amplitude and the duration of associated fetal body movements in 44 normotrophic and 40 hypotrophic fetuses (body weights within the 6th to 10th percentiles, n = 19, and less than or equal to the 5th percentile, n = 21) between the 36th and 40th gestational weeks. Related to the duration of associated fetal body movements, hypotrophic fetuses proved to have gradually smaller heart rate accelerations than normotrophic fetuses. Moreover, the acceleration parameters duration and amplitude were dependent on the relative duration of fetal body movements. Short fetal body movements were accompanied by fetal heart rate accelerations of relatively highest degree and vice versa. As a consequence, no comparison is possible between temporally different fetal body movements and their associated heart rate accelerations. Of the two acceleration parameters duration and amplitude, the inclusion of the accelerations amplitude in the above mentioned ratio yielded the most obvious results. Taking into consideration that fetuses with intrauterine growth retardation are often in a state of chronic hypoxia, the ratios of acceleration amplitude and durations of associated fetal body movements indicated different degrees of this metabolic situation.     

The relationship between fetal heart rate accelerations, fetal movements, and uterine contractions

The association between fetal heart rate (FHR) accelerations and fetal movements during uterine contractions was studied in 52 pregnant women near term or at the beginning of labor. FHR and uterine contractions were recorded by tococardiograph. At the same time, fetal movements, whether associated or not with contractions, were viewed by real-time ultrasound. During uterine contractions, 95.5% of the FHR accelerations were associated with fetal movements. Also, 90.9% of the accelerations which appeared when the uterus was not contracting were associated with fetal movements. Fetal movements were not seen in 91% of uterine contractions which were not associated with FHR accelerations. The suggestion is made that uterine contractions stimulate both fetal movements and FHR accelerations.     

Patterns of fetal breathing activity in the human fetus at 24 to 28 weeks of gestation

Continuous 24-hour observations of fetal breathing were performed in 20 normal, pregnant women between 24 and 28 weeks' gestation by real-time ultrasound. Fetuses made breathing movements approximately 14% of the time. No change in breathing activity after a maternal meal was observed, but a significant increase in the incidence of fetal breathing activity was noted overnight. Fetuses at 24 to 28 weeks' gestation breathed at a rate of 44 breaths per minute, and the longest period of apnea noted was 14 minutes. These data suggest that the pattern and incidence of fetal breathing at 24 to 28 weeks' gestation are different from those of fetuses observed in the last 10 weeks of pregnancy. A maturational process in the control of fetal breathing may explain these observations.     

Patterns of human fetal heart rate accelerations from 26 weeks to term

Computerized analysis of the distribution of 2598 fetal heart rate accelerations in 83 healthy fetuses at 26 to 40 weeks' gestation demonstrated that the currently used definition of an acceleration as greater than or equal to 15 beats/min for greater than or equal to 15 seconds is applicable only after 30 weeks' gestational age in fetuses with a basal fetal heart rate of less than or equal to 128 beats/min. A significant negative correlation was found between the mean hourly basal fetal heart rate and the mean amplitude of fetal heart rate accelerations from 30 weeks to term. There was also a significant maturational process in the pattern of fetal heart rate and fetal heart rate accelerations that occurred between 26 and 28 and between 30 and 32 weeks; this was characterized by a decrease in basal fetal heart rate, an increase in the amplitude of fetal heart rate accelerations, and an increase in long-term fetal heart rate variability.     

The relationship between gestational weeks and fetal breathing movements in each pattern of the fetal heart rate

Fetal breathing movement (FBM) was analysed in each fetal heart rate (FHR) pattern and the gestational 2 weeks. FHR pattern was divided in automated FHR analysis into 3 groups; active, intermediate and resting patterns. The patients consisted of 102 pregnant women at 30-41 weeks, including 13 complicated pregnancies. 1) The active pattern percentage was 52.7% at 32-33 weeks and it decreased gradually. That of the resting pattern was 25.5% at 32-33 weeks and it increased gradually. 2) The percentages of positive FBM in the active pattern were significantly larger than those in the resting pattern in each 2 weeks. 3) The duration of continuous FBM ranged from 3 to 202 sec. FBM of long duration tended to exist in the resting pattern rather than in the active pattern. 4) The percent time ratio of FBM ranged from 1.0 to 92.7% and showed no definite relationship with the FHR patterns or gestational weeks. 5) The FBM rates in each FHR pattern showed no significant differences. Their sequential differences after 36 weeks were significant; that is, FBM in the resting pattern was more regular than that in the active pattern. 6) In high risk pregnancy, the resting pattern percentage was 52.3% and the ratio of positive FBM in the resting pattern was significantly smaller than that in active pattern.     

Antepartum fetal heart rate monitoring: III. Fetal movements and accelerations in fetal heart rate

This third part of the paper deals with the study of the relationships between fetal movements, fetal heart rate accelerations associated with such movements, fetal heart rate instability and neonatal outcome.No correlation has been found between absence of fetal movements and neonatal distress.A correlation has been found between the lack of fetal heart rate accelerations, the flatness of the record and poor neonatal outcome.In extreme situations (i.e. flatness in less than 10% of the record or in more than 80%) the presence or absence of accelerations does not add further useful information. Such information, however, is gained in the intermediary situations (the ‘combined’ recordings) and particularly when the record is between 51 and 80% flat where there appears to be an 85.6% risk to the fetus.Consequently, when trying to analyse an antenatal record it seems advisable to take primarily into account the percentage of flat recordings (providing the records are numerous enough and of sufficient length). Then, in records between 10 and 50% flat, the presence or the lack of spontaneous decelerations requires consideration whereas, when the record is between 51 and 80% flat, it is the presence or absence of fetal heart rate accelerations which is important.     

Transvaginal ultrasound measurements of the fetal heart at 11 to 17 weeks of gestation.

The scope of this article is to report on transvaginal ultrasound measurements of the fetal heart, which were performed in 124 healthy fetuses at 11 to 17 weeks of gestation. Normative growth charts were constructed. Statistical analysis demonstrated linear correlation (y = a + bx) between gestational age and measurements of the right and left ventricles. The ratio between fetal heart and the transverse diameter of the chest was found to be nearly constant at these gestational ages.     

The clustering of fetal heart rate changes and fetal movements in pregnancies between 20 and 30 weeks of gestation

The temporal organization (nonrandomness) of fetal heart rate (FHR), fetal movement, and their association was evaluated in 20 normal pregnancies at 20 to 22 or 28 to 30 weeks of gestation with the use of external electronic fetal monitoring and statistical analysis with the runs test. At 20 to 22 weeks, significant clustering was found in one of 10 pregnancies for FHR change, two of 10 pregnancies for fetal movement, and one of 10 pregnancies for FHR changes associated with fetal movement. At 28 to 30 weeks, significant clustering was found in eight of 10 pregnancies for FHR change, eight of 10 pregnancies for fetal movement, and uli 10 pregnances for FHR change associated with fetal movement. There was significantly more clustering of FHR change, fetal movement, and FHR change associated with fetal movement at 28 to 30 weeks of gestation than at 20 to 22 weeks of gestation. Clustering of FHR changes was highly correlated with clustering of fetal movement.     

Evaluation of the fetal movements and accelerations of fetal heart rate in twin pregnancy

In twin pregnancy, the fetal heart rates (FHR) of each fetus and uterine contraction were recorded simultaneously on a single recording chart by two cardiotocographs and a linear multichannel recorder. In addition, with a new technique, FHR and fetal movement (FM) signal bursts for each fetus were recorded similarly on a single recording chart by two ultrasonic Doppler actographs and an electronic polyrecorder. Simultaneous nonstress tests were done for 32 sets of twins at 28 to 41 weeks' gestation. The observed acceleration number in every gestational week increased till 38 weeks and this result was similar to that in singletons. Completely synchronous acceleration patterns in the 2 fetuses were observed in 654 recordings (31.4%) and asynchronous acceleration patterns in 1,108 recordings (53.1%). Simultaneous FHR and FM signal burst recordings were performed in 7 twin pregnancies. In about half of the 1,535 recordings, the FM signal bursts were synchronous between 2 fetuses, whereas they were asynchronous in the other half. Synchronous FM bursts in each gestational week decreased with time. Neurological independency between the twins was suggested by the results. The synchronous appearance of FM signal bursts with FHR accelerations of 2 fetuses was more pronounced in a uniovular twin than in a biovular twin.