Fetal breathing movements and fetal distress.

Twenty-seven pregnancies were monitored by antenatal cardiotocographs, daily fetal movement counts and an assessment of fetal breathing activity by real time scanning, and the results of these tests were related to the development of fetal distress during the first stage of labour. The proportion of time during which fetal breathing movements were present, determined over only a short period of time, was found to be a useful predictor of fetal behaviour during a labour.     

Fetal breathing movements: antepartum monitoring of fetal condition.

Until recently, the relative inaccessibility of the human fetus to physical assessment has made antepartum assessment of its condition difficult. The development of methods for accurate antepartum fetal heart rate monitoring and the subsequent study of heart rate responses to various stimuli have resulted in a significant improvement in accuracy of antepartum fetal surveillance. The development of real time B-mode ultrasound enables the clinician to assess many additional fetal biophysical variables including fetal breathing movements. In our observations, the combination of heart rate and fetal breathing assessment has produced a significant improvement in differentiating the normal from the compromised fetus. The addition of other biophysical variables (tone, movements and amniotic fluid volume) have further refined the ability to identify the fetus at risk. At this point, we have evaluated only a few of many possible variables. It seems probable that, as other fetal biophysical variables are included with the overall assessment, for example fetal reflexes or fetal biophysical response to exogenous stimuli, the identification of the fetus at risk and the quantitation of the magnitude of risk will become increasingly more precise.     

Fetal breathing movements and maternal exercise.

Earlier statements that fetal breathing movements (FBM) are sensitive to changes in the fetal homeostasis prompted the study of the effect of maternal exercise on FBM and fetal heart rate. Forty women in the last trimester of gestation were subjected to a work load (80 W) for 5 min on a bed ergometer cycle; in 30 of them FBM were recorded by A-mode ultrasound, and in 10, the fetal heart rate was monitored by continuous ultrasound. Maternal blood pressure, pulse rate, blood pH and pCO2, and transcutaneous pO2 were also followed. The FBM showed a transient marked increase in incidence immediately after the end of the exercise. No changes in basal level or in baseline variability of the fetal heart rate were found in the recovery period after work. Some possible causes of the observed FBM alterations are discussed. The findings imply that, after this particular form of stress, FBM are a more sensitive indicator of the physiological state of the fetus than the fetal heart rate.     

Ultrasonographic patterns of fetal breathing movements in normal pregnancy

Objective: To assess through pregnancy fetal breathing movements (FBMs) patterns detected by M-mode and Doppler velocimetry technology. Methods: In this cross-sectional study FBMs were investigated in 1882 uncomplicated pregnancies over a 4-year period. Abdominal and thoracic wall movements of fetuses between 14 and 40 weeks of gestation were studied by M-Mode scan, and color Doppler velocimetry with spectral imaging analysis was used to investigate the presence of FBMs associated with nasal fluid flow velocity waveforms (NFFVWs). Results: Abdominal movements were observed in 19% of cases when gestation was less than 20 weeks and in 61% of cases when it was between 21 and 25 weeks; chest movements were significant after 21 weeks; and NFFVWs were detected at 22 weeks and increased progressively to 93% of cases at term. Conclusions: Fetal breathing movements are a complex phenomenon with a composite, progressive pattern of development during gestation.     

Maternal hypoxemia and fetal breathing movements.

Fetal breathing movements (FBM) were observed daily using a real-time B-mode ultrasound method in a patient with sickle cell anemia in crisis. Observations were made on 2 occasions in the presence of maternal hypoxemia (PO2 less than or equal to 40 mmHg), and FBM were noted to be absent. Conversely, when maternal PO2 was 60 mmHg or greater, FBM were present 23--80% of the time. The FBM were reduced or absent within 90 minutes of maternal Demerol injection. These observations suggest that the human fetal response to hypoxemia may be similar to that observed under expermental conditions in the animal fetus.     

Cigarette smoking and fetal breathing movements.

Cigarette smoking caused a reduction in the incidence of fetal breathing movements in normal and abnormal pregnancies. The size of the reduction varied, being greatest in small-for-dates pregnancies and pregnancies complicated by fetal distress in labour and least in pre-eclamptic pregnancies. The fall in the amount of fetal breathing movements was significantly related to the rise in maternal plasma nicotine after smoking but was unrelated to the rise in barboxyhaemoglobin. Smoking non-nicotine (herbal) cigarettes produced increases in carboxyhaemoglobin concentrations similar to those observed after smoking tobacco cigarettes, and was not associated with a fall in the incidence of fetal breathing movements. Chewing gum containing nicotine produced rises in plasma nicotine concentration similar to those observed after smoking tobacco cigarettes and was associated with a significant reduction in the incidence of fetal breathing movements. Hence nicotine appeared to be the factor in cigarette smoke responsible for the reduction in the incidence of fetal breathing movements. Nicotine was present in the cord blood of infants whose mothers smoked. The possible mechanism by which nicotine caused a reduction in the incidence of fetal breathing movements and its possible relevance to the detrimental effects of smoking on the fetus are considered.     

Fetal heart rate and fetal movements.

Fetal Heart Rate (F.H.R.) in association with fetal movement was evaluated in 141 normal and pathological pregnancies. In the normal cases only 31% showed an acceleration of F.H.R. in association with fetal movement. The majority of the normal cases, 62%, did not demonstrate changes in F.H.R. in association with fetal movement. In the pathological pregnancies there were no characteristic changes in F.H.R. associated with fetal movement. It appears that F.H.R. acceleration associated with fetal movement cannot be used as an index for fetal well being.     

Intrauterine breathing movements and fetal presentation

Fetal breathing movements in 14 twin pregnancies were examined with ultrasonic technique. The twin fetuses I in cephalic presentation showed a significantly higher percentage of apnea and periodic breathing compared with twin fetuses II. No such difference was found in twin pairs with Twin ti in breech presentation. Also in the control group of 27 singleton pregnancies, the fetuses in cephalic presentation had a higher incidence of apnea and periodic breathing than those in breech presentation. The position of the fetus seems to be decisive for the character of the breathing movements before birth.     

Maternal smoking and fetal breathing movements

Pregnant, habitually smoking women were studied during the last trimester when smoking a standard cigarette, smoking a nontobacco cigarette, or chewing a piece of chewing gum containing 2 or 4 mg. of nicotine. The effects of the experimental interventions were followed on the concentration of nicotine and the percentage of car?yhemoglobin (COHb) in maternal blood, on the amount and pattern of the fetal breathing movements, and on the maternal heart rate, breathing rate, and blood glucose level. The maternal blood concentration of nicotine was increased by the standard cigarette, the 4 mg. nicotine chewing gum, and the 2 mg. nicotine chewing gum in descending order. The COHb percentage in maternal blood was increased by the standard cigarette and to a lower degree by the nontobacco cigarette. A significant increase of apnea and periodic breathing movements in the fetus followed the smoking of a standard cigarette; a similar but nonsignificant change occurred in a dose-related way after the 4 mg. and the 2 mg. chewing gum. The maternal heart rate was positively correlated to the level of blood nicotine. Nicotine appears to be partly responsible for the transient reduction of the fetal breathing movements occurring after smoking one standard cigarette. The suppression of the fetal breathing movements in utero poses the question whether iterated maternal smoking might influence the prenatal assessment of fetal maturity using determination of pulmonary surfactants in the amniotic fluid.     

Fetal breathing movements and the nonstress test in high-risk pregnancies.

Three hundred ninety-eight observations of fetal breathing movements (FBM) and the nonstress test (NST) were made in 223 patients. The presence of FBM was noted in a significantly higher proportion of tests with a reactive NST (88%) than a nonreactive NST (67%). Conversely, a significantly higher proportion of tests were reactive when FBM were present (82.6%) than when FBM were absent (49%). A significant relationship existed betweeen either test and the outcome of pregnancy as judged by the five minute Apgar score or the incidence of fetal distress in labor. Combining two normal tests did not improve the accuracy in predicting outcome; but the combination of both tests, when abnormal, produced a significant improvement in predicting fetuses likely to have an abnormal outcome. The combination of the normal with the abnormal test had a predictive accuracy similar to a single normal test in predicting a normal five-minute Apgar. This combination was associated with an incidence of fetal distress in labor intermediate between that seen with either the normal or abnormal test when alone. Neither a single test nor the combination of tests was helpful in identifying the small-for-gestational age (SGA) infants. These data indicate antepartum fetal evaluation may be improved when more than one biophysical variable is used.     

The variability of fetal breathing movements in normal human fetuses at term

With the use of a B-scan phase-locked tracking system, 108 observations of fetal breathing were performed on 97 normal antenatal patients at term. One hundred thirty-three recorded segments of fetal breathing movements were obtained. Breath-to-breath variability was analyzed in 79 segments and expressed as a coefficient of variability. The mean coefficient of variability was 28.6% ± 13.2%, and a histogram plot revealed a normal distribution. All fetuses had normal antepartum testing and all Apgar scores and neonatal courses were normal. The potential application of human fetal breathing variability as a test for fetal health is discussed.     

The relationship between fetal activity and behavioral states and fetal breathing movements in normal and growth-retarded fetuses

The incidence of fetal breathing was studied during the course of behavioral state observations on 28 low-risk fetuses between 32 and 40 weeks' gestational age and on 12 growth-retarded fetuses between 36 and 40 weeks. Real-time ultrasound scanners were used to detect fetal eye, body, and breathing movements, and the fetal heart rate was recorded continuously. The mean duration of the observation sessions was 110 minutes. The mean incidence of fetal breathing was greater during periods of fetal activity (body and eye movements present, greater heart rate variability) than during quiescence (body and eye movements absent, narrowed heart rate variability) at all gestational ages studied in both low-risk and growth-retarded fetuses. During periods when one of the state variables (body movements, eye movements, heart rate pattern) was in its active condition while the other two were quiet, or the reverse, the incidence of fetal breathing was intermediate between those found when all three state variables were in agreement. After behavioral states had developed, at 38 and 40 weeks, the mean incidence of fetal breathing in the low-risk fetuses was greater during active states than during the quiet state. There was no apparent increase in the degree of linkage between fetal breathing and other expressions of fetal activity after the emergence of behavioral states.     

Fetal breathing movements and the abnormal contraction stress test.

The presence or absence of fetal breathing movements (FBMs) in a 30 minute observation period was determined in 29 patients with abnormal contraction stress tests (CSTs). The study population included 14 patients with positive CSTs, 11 patients with equivocal CSTs, and four patients with unclassified CSTs. In patients with either an equivocal or a positive CST, the presence of FBMs was associated with a high incidence of false predictive tests. Conversely, the absence of FBMs in a patient with a positive CST was uniformly associated with intrapartum fetal distress. The presence or absence of FBMs was not helpful in assessing the patients with unclassified CSTs. These data suggest FBMs may be a useful means of evaluating the patient with a positive or equivocal CST.     

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.     

Fetal breathing movements in the normal and growth-retarded human fetus: a multiscan/M-mode echofetographic study.

52 women were examined, between the 25th and 40th wk of pregnancy, during the day-time, by the echographic multiscan/M-mode technique. Definitions of normal fetal breathing movements and singultus fetalis movements were determined. In normal pregnancies fetal breathing movements occurred during 12-19% of the total observation time before the 39th wk of pregnancy but only during 6-9% of the observation time in the 39th or 40th wk. In low birth weight pregnancies fetal breathing movements occurred during 8-13% of the total observation time, and the incidence was the same before and after the 39th wk. Singultus fetalis movements occurred in normal and low birth weight pregnancies.     

Fetal breathing movements in oligohydramnios are not increased by aminoinfusion.

OBJECTIVE: To determine whether fetal breathing movements (FBM) in pregnancies with oligohydramnios change with restoration of amniotic fluid volume. DESIGN: A prospective experimental study. SETTING: Fetal Medicine Unit, tertiary referral hospital. SUBJECTS: 16 women with singleton pregnancies complicated by severe oligohydramnios. INTERVENTIONS: Restoration of amniotic fluid volume by transabdominal amnioinfusion. Controls comprised pregnancies in which infused fluid leaked vaginally, so that oligohydramnios was not corrected. MAIN OUTCOME MEASURES: Change in total breathing movements, change in FBM incidence derived from 40 min recordings immediately before and after amnioinfusion. RESULTS: There was no significant difference in the change in total breathing movements or in the change in incidence of FBM between the 10 pregnancies in which amniotic fluid volume was restored, and the other six in which fluid leaked after infusion and volume was not restored. In both groups, there was no significant change with infusion in number of FBM (mean change -72, 95% CI -218 to +74 in the fluid-retained group and -64, 95% CI -273 to +145 in the fluid-leaked group) and incidence of FBM (median change -2.5%, range -27 to +10 in the fluid retained group and -4.5%, range -34 to +15 in the fluid-leaked group). CONCLUSIONS: This study suggests that restitution of amniotic fluid volume in human pregnancies complicated by severe oligohydramnios does not acutely alter the incidence of FBM. These data support an increasing literature suggesting that impairment of fetal breathing is not the mechanism for oligohydramnios-related pulmonary hypoplasia.     

Fetal breathing,gross fetal body movements,and maternal and fetal heart rates before spontaneous labor at term

In order to examine patterns of fetal breathing and body movements and fetal and maternal heart rates near term, we studied 28 healthy pregnant women over 24-hour observation intervals at 38 to 40 weeks' gestation. There was a significant decrease in the incidence of fetal breathing movements during the last 3 days before spontaneous parturition at term, but there was no significant difference in the patterns of gross body movements or fetal and maternal heart rates. We concluded that, prior to spontaneous labor at term, there is a normal decrease in the incidence of fetal breathing movements but no similar change in the incidence of gross fetal body movements. This study suggested that the presence of gross fetal body movements is a more consistent index of fetal health before spontaneous labor at term.     

Fetal breathing movements before oxytocin induction in prolonged pregnancies

Fetal breathing movements were recorded before elective labor induction in 65 patients with uncomplicated prolonged pregnancies. Breathing activity was observed in 41 patients and was absent in 24. Comparison of these two groups indicated that the induction period was significantly shorter and the oxytocin requirement significantly lower in the group with no fetal breathing movements (mean, 319.3 vs 648.5 minutes and 1133.7 vs 2708.4 mIU, respectively). These findings remained valid regardless of Bishop scores. The data suggest that fetal breathing movements are predictive of the effectiveness of oxytocin induction in prolonged pregnancies.