Human Fetal Breathing Movements Research Articles

The effect of intermittent maternal fasting on human fetal breathing movements

In order to determine the effect of maternal fasting on human fetal breathing movements (FBM), 63 healthy pregnant women with singleton uncomplicated pregnancies of 30 weeks' gestation or more, and who were fasting during Ramadan, were recruited. Maternal blood glucose level and fetal movements were recorded during and after fasting. Statistical comparison of samples before and after a meal was made using Wilcoxon's signed-ranks test. Maternal glucose level during fasting (5.1 ± 0.5 mmol/l) was significantly (P = 0.01) lower than after breakfast (5.3 ± 1.0 mmol/l). There was a significant association between maternal glucose levels and numbers of days faster (P = 0.01). The time needed to detect breathing movements was significantly longer (P = 0.005) during fasting than postprandial. The continuous variety of fetal breathing movement was significantly (P = 0.02) less during fasting compared to postprandial. It is concluded that intermittent maternal fasting is associated with a significant alteration in the frequency and pattern of human FBM.

The intercostal-to-phrenic inhibitory reflex in the human fetus near term

Human fetal breathing movements (FBM) differ from neonatal breathing in that they are predominantly paradoxical and are not present all the time. Respiratory pauses are common in the fetus while prolonged apneas are life-threatening in the neonate. In the latter they occur during state 2 (active sleep) when paradoxical breathing is more frequent. Then the inward movement of the thoracic wall causes spreading of the caudal ribs which may elicit an intercostal-to-phrenic inhibitory reflex (IPIR) leading to apnea. This is not the case in state 1 (quiet sleep). In the fetus similar sleep states, state 2F and 1F respectively, have been identified and we investigated if the IPIR is already present before birth and if so, if the response is different between 1F and 2F. In 21 healthy fetuses between 37 and 40 weeks, two real time scanners and a cardiotocograph were used to asses the fetal behavioural state, If FBM were present, the caudo-lateral part of the fetal thoracic wall was shortly compressed manually and the period that FBM ceased measured. During the same epoch moments of shamstimulation, i.e. control periods without actual compression were also carried out. In 15 out of 16 fetuses with FBM in 1F, and in 19 out of 19 fetuses in 217, compressions were immediately followed by an apnea. In contrast, moments of shamstimulation never induced apnea, indicating that the IPIR is indeed present in both behavioural states. The mean apnea duration in 1F (29 compressions) was 13.9 ±9.1 s (range 4–37 s), in 2F (31 compressions) 18.3 ±12.7 s (range 4–48 s). These results were not significantly different. We conclude that the IPIR is already present in utero and can be induced by manual compression of the thoracic wall. Furthermore, although breathing is less frequent and much more regular during IF, the effect of the IPIR seems to be similar in 1F and 2F in the healthy near term fetus.

The role of carbon dioxide in the generation of human fetal breathing movements

To determine the role of carbon dioxide in the generation of fetal respiratory movements, the effect of induced matermal hypocapnia and hypercapnia on fetal breathing movements, gross body movements, and fetal heart rate was studied in 12 healthy pregnant women near term. Patients were studied for a 1-hour control period breathing room air followed by four randomized 15-minute study periods with patients breathing either room air, a prepared gas mixture with 2% or 4% carbon dioxide, or undergoing controlled hyperventilation as determined by monitoring end-tidal PCO2. The percentage of time fetal breathing movements correlated significantly with maternal end-tidal PCO2 (r = 0.62, p < 0.01), increasing with maternal breathing of 2% and 4% carbon dioxide and decreasing with maternal hyperventilation. Fetal gross body movements, fetal heart rate, and fetal heart rate variability showed no significant changes. It is concluded that as in adults, the carbon dioxide level in fetuses is an important stimulus for the generation of respiratory movements, acting independent of a change in behavioral state. It is hypothesized that tonic carbon dioxide level input is an important determinant of fetal respiratory center drive, but little or no phasic carbon dioxide input exists because of continuous placental excretion, thus resulting in the episodic occurrence of breathing movements with changes in the fetal behavioral state.

The effects of long- and short-term maternal caffeine ingestion on human fetal breathing and body movements in term gestations

The possible effects of long- and short-term maternal ingestion of caffeine during normal human pregnancy on the breathing and body movements of third-trimester fetuses were studied in 14 patients, selected by a dietary questionnaire, and divided into two equal groups: high consumers (greater than 500 mg/day) (group 1) and low consumers (less than 250 mg/day) (group 2). All mothers followed a standard study protocol and underwent overnight fasting; studies began with a 30-minute control period, followed by oral administration of 200 mg caffeine, and a 180-minute subsequent observation period with continued maternal fasting. Blood samples for glucose and caffeine were obtained every 30 minutes and continuous recording of fetal breathing and body movements were entered on a microcomputer for off-line analysis. The two groups were similar for all obstetric outcome features. Plasma glucose levels were similar and constant in both groups whereas caffeine levels increased significantly at 60 minutes after administration; mean plasma caffeine levels were significantly higher in group 1 than in group 2 at all intervals. Fetal breathing rates and body movement incidences were similar in both groups before and after caffeine administration. Fetal breathing movement incidence decreased significantly in group 2 but was sustained at baseline levels in group 1 throughout the study. High long-term ingestion of caffeine during pregnancy is associated with higher maternal plasma caffeine levels and fetal breathing activity when compared with low caffeine ingestion. Short-term administration of 200 mg caffeine does not appear to have a significant physiologic impact on these activities.

Effects of vibratory acoustic stimulation on human fetal breathing and gross fetal body movements near term

Twenty-five pregnant women between 36 and 40 weeks' gestational age were studied to examine effects of a 5-second external vibratory acoustic stimulus on fetal breathing and gross fetal body movement patterns. When the study period was compared with the control period, there was an immediate significant decrease in the incidence of fetal breathing movements that persisted for 1 hour after the stimulus. Moreover the fetal breathing pattern was more irregular for the hour after the stimulus. There was also a significant but delayed increase in the incidence of gross fetal body movements that persisted for 1 hour after the stimulus. We hypothesize that an external vibratory acoustic stimulus causes a change from a state of sleep to a state of wakefulness in near-term healthy fetuses.

Effects of maternal glucose ingestion on human fetal breathing movements at weeks 24 and 28 of gestation

The incidence of human fetal breathing movements was studied in normal pregnancies before and after administration of 50 g glucose or a placebo (water) at 24 and 28 weeks. Glucose or water was given to the same women on two separate days in a randomised order. No significant differences were present among the results on the placebo-day and the control period of the glucose-day at either gestational age. On the glucose-day, the incidence rose significantly from 3.6 to a maximum of 11.6% at 24 weeks, and from 6.7 to 30.2% at 28 weeks. At both ages the maximum was found 90–120 min after the intake of glucose. It is concluded that already at 24 weeks gestation the human fetus reacts with an increase of fetal breathing movements after the administration of glucose to the mother.

The rhythmicity of fetal breathing varies with behavioural state in the human fetus

The rhythmicity of human fetal breathing movements was studied during two different behavioural states (1F and 2F, respectively), using real-time B-scan-directed M-mode ultrasound recordings. The mean breath-to-breath interval durations and the standard deviations (SD), and the standard deviations of the interval differences (SDDSI) were calculated. The mean breath-to-breath interval duration was not significantly shorter during 1F than during 2F. SD and SDDSI, however, showed significantly lower values during 1F, demonstrating that the fetal breathing rhythm is more regular during state 1F than during state 2F epochs. Regular fetal breathing is thus a concomitant of state 1F.

Effects of Intravenous Glucose Injections on Human Fetal Breathing Movements and Gross Fetal Body Movements at 38 to 40 Weeksʼ Gestational Age

Bocking, A.; Adamson, L.; Cousin, A.; Campbell, K.; Carmichael, L.; Natale, R.; Patrick, J. Author Information

Human fetal breathing movements after carbohydrate ingestion in fasting and nonfasting subjects

Human fetal breathing movements were observed by means of the linear array real-time B-scan technique in 40 study sessions at 35 to 36 weeks' gestation. Fasting and nonfasting subjects received water or 75 gm of glucose orally. Fetal breathing activity, observed as movement of the chest wall, was analyzed. The data support conclusions that fetal breathing increased after maternal ingestion of glucose in both fasting and nonfasting subjects, that the absolute increases in fetal breathing were similar for fasting and nonfasting subjects, and that fetal breathing occurred more frequently in nonfasting control subjects than in fasting control subjects in the setting of the study.

Effects of intravenous glucose injections on human fetal breathing movements and gross fetal body movements at 38 to 40 weeks’ gestational age

Fetal breathing movements and gross fetal body movements were studied subsequent to the intravenous injection of either 25 gm of glucose or an equal volume of normal saline solution in 10 healthy women with uncomplicated pregnancies at 38 to 40 weeks' gestation. The incidence of fetal breathing increased from 17.5% during the control period to 54.9% after glucose injection. Neither glucose nor saline solution had any effect on the incidence of gross fetal body movements. All fetuses made some breathing movements during any 15-minute interval between 30 and 75 minutes after glucose injection. These data suggest a useful strategy for clinical measurement of fetal breathing activity near term.

Effects of synthetic glucocorticoid administration on human fetal breathing movements at 34 to 35 weeks' gestational age

Fetal breathing movements were measured in six women who had received exogenous glucocorticoids throughout pregnancy and in whom the endogenous circadian rhythm in cortisol was absent or had been suppressed. Studies were performed for 24-hour observation periods while women received prednisone and then one week later on the same women after equivalent doses of dexamethasone. Fetal breathing movements occurred 29.9% ± 1.9% of the time in the prednisone-treated group and this was not changed in the same fetuses after dexamethasone treatment. There was a significant increase in the percentage of time spent making breathing movements during the second and third hours following breakfast, lunch, and dinner (P < 0.001). A fourth peak in fetal breathing activity occurred in the late evening and seemed to be related to the time of the evening glucocorticoid medication. These data were compatible with the hypothesis that maternal glucocorticoid concentrations may influence patterns of fetal breathing movements at 34 to 35 weeks' gestational age.

Fetal age and patterns of human fetal breathing movements

Human fetal breathing movements have been studied serially from 20 weeks to the onset of labor in eight normal primigravid patients. Real-time ultrasound was used and the events of the study period were analyzed visually and by computer processing of a punched paper tape record. Studies were performed before and after a maternal glucose load. The pattern of fetal breathing movements changed with increasing fetal age. The breathing rate decreased and became more regular toward term. The form of each breath altered with gestational age. Prior to 32 weeks the breath time was short. Between 32 and 36 weeks a breath characterized by a long inspiratory phase with multiple augmenting movements was seen. After 36 weeks the breath was more uniform. A definite periodicity was seen in the last 2 weeks of pregnancy, with episodes of shallow, more regular breathing and a more variable pattern. Glucose intake did not alter these patterns.

Human fetal breathing activity during electively induced labor at term

Human fetal breathing movements were measured during the first stage of electively induced labor in 20 healthy term pregnancies. Fetuses made breathing movements 25.6% of the time during a 1 hour control period and breathing decreased significantly to 8.3% during latent-phase labor and further decreased to 0.8% during active labor (P < 0.001). Patterns of increased fetal breathing activity accompanied by increased gross fetal body movements and increased fetal heart rate variability for periods of 20 to 60 minutes out of every 1.0 to 1.5 hours were observed, and the intermittent patterns of increased body movement and heart rate variability continued throughout the first stage of labor despite the decrease in fetal breathing activity during latent- and active-phase labor. It will be important to account for rest activity patterns when interpreting variability of heart rate during labor. The absence of fetal breathing activity during electively induced labor at term is not a clinical indicator of fetal ill health.

Patterns of human fetal breathing activity at 34 to 35 weeks' gestational age

Continuous measurements of human fetal breathing movements at 34 to 35 weeks' gestational age were made with an ultrasonic real-time scanner for periods of 24 hours in 11 women. A significant increase occurred in fetal breathing activity during the second and third hour following meals and this pattern apparently followed an increase in maternal plasma glucose concentration. There was a prolonged significant increase in fetal breathing activity between 0100 and 0700 hours. Increases in human fetal breathing activity accompanied by increased gross fetal body movements occurred for periods of 20 to 60 minutes out of every 1.0 to 1.5 hours of observation time. It was concluded that the percentage of time spent breathing by normal fetuses was related to time of day and maternal meals. The alternating changes of fetal activity and inactivity observed may represent biologic changes of sleep state in the human fetus in utero at 34 to 35 weeks' gestational age. It will be important to account for these three patterns of fetal breathing activity in clinical studies which examine the usefulness of fetal breathing movements in assessing fetal health.

Maternal ethanol ingestion and the occurrence of human fetal breathing movements

The study of the development of fetal breathing movements in human gestation may provide an increased understanding of maturation of the functional central nervous system (CNS). In seven term pregnancies low maternal blood alcohol levels suppressed fetal breathing movements. No effects on fetal oxygenation or acid-base status were demonstrated at the low blood alcohol level. The suppression is therefore most consistent with a direct effect of alcohol on the fetal CNS. This investigation provides further support of the thesis that fetal breathing movements reffect some components of fetal CNS activity.

Effects of human maternal venous plasma glucose concentrations on fetal breathing movements

Human fetal breathing movements were studied following the maternal ingestion of either a 50 Gm. oral glucose load or an equal volume of water in 22 healthy women with uncomplicated pregnancies at 32 to 34 weeks' gestation. The percentage of time spent breathing in fetuses of glucose-treated mothers increased from 23.2 ± 2.2 per cent during the control period to a maximum of 58.9 ± 5.2 per cent at 105 minutes following the oral glucose load (p < 0.01) which was one hour following the peak maternal plasma glucose concentration. No similar increase in maternal glucose concentrations or percentage time spent breathing occurred in patients receiving water. Fetal breathing movements were observed in 97 per cent of the 15 minute periods during the second and third hour after maternal ingestion of a 50 Gm. oral glucose load. It was concluded that maternal carbohydrate intake two hours prior to fetal breathing observations should be documented to permit adequate interpretation of fetal breathing activity.

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. Analysis 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.

FETAL EVALUATION BY REAL-TIME IMAGING

The application of real-time imaging to the study of fetal morphology and function is an exciting advance. Rapid accurate study of fetal dynamics is possible with this apparently safe, noninvasive technique. Animal studies have revealed the general physiology of fetal breathing movements, which are now under extensive investigation with real-time imaging in the human. There is evidence for circadian rhythm of human fetal breathing movements as well as a relationship to maternal substrate loading. The presence of fetal breathing movements of the rapid irregular type may be a reassuring sign in the presence of other indicators of fetal compromise. Using real-time B-scan imaging, we have found long periods of apnea in pregnancies with normal perinatal outcome. As suggested in the animal studies, changes in fetal breathing patterns prior to fetal death may be more complex than originally thought. The techique of real-time B-scan imaging with precise definition of apnea, general movements, and fetal breathing will provide valuable information on which to base our evaluation of the clinical usefulness of fetal breathing movement studies in the management of pregnancy.

Device for measurement of fetal breathing movements--I. The TD-recorder. A new system for recording the distance between two echogenerating structures as a function of time.

<h2>Abstract</h2> A new device (time-distance recorder; TD-recorder) is presented for the measurement of the relative movements of two echoes visualized by a two-dimensional real-time scanner. One of the real-time image lines is selected and the instant distance between two echoes, indicated by markers, is assessed on-line. The output analog signal passes through a slew-rate filter which is activated by disturbing signals. During the measurement the ultrasonic energy output of the scanner can be considerably reduced by a low intensity mode facility. The system was originally developed for recording human fetal breathing movements.

Doppler ultrasound method for detecting human fetal breathing in utero.

An audible Doppler ultrasound method for detecting human fetal breathing movements in utero has been developed. The frequencies synchronous with fetal breathing movements probably originate from the lung rather than the chest wall. This method is much cheaper and simpler than the ultrasound A-scan method and is suitable for screening large numbers of people.