Acute effect of maternal smoking on the human fetal blood flow

Summary. The immediate effect of maternal smoking of one cigarette on blood flow in the descending thoracic aorta and umbilical vein was studied in 19 fetuses at between 29 and 39 weeks gestation. Blood flow was measured with a combined real-time ultrasound and Doppler ultrasound technique immediately before smoking and immediately after cessation of smoke inhalation. The measured flow changes immediately after maternal smoking were insignificant and suggest that the haemodynamic and chemical effects of smoking in the mother do not produce immediate alterations in the blood flow in the fetal thoracic aorta or in the umbilical vein.     

Acute effects of maternal smoking on fetal hemodynamics.

OBJECTIVE: To investigate acute effects of cigarette smoking on fetal hemodynamics. METHOD: Sixty seven women between 32nd to 40th weeks of gestation were evaluated. Maternal blood pressure and heart rate, fetal heart rate (FHR) tracing, umbilical and fetal middle cerebral arterial (MCA) color Doppler measurements were evaluated. Pre- and postsmoking results were compared with paired t-test. RESULTS: Maternal heart rate significantly increased after smoking. Baseline FHR and FHR variability remained unchanged. The number of participants who had a reactive NST was 60 in 67 before smoking (89.5%) and decreased to 47 after smoking (70.1%) (p=0.009). There were no significant changes between maximum and minimum flow velocities, pulsatility index (PI), resistance index (RI) and systolic/diastolic flow ratio (S/D) of umbilical and middle cerebral arteries. CONCLUSION: The nicotine load of a single cigarette may be inadequate to cause a detectable decrease in utero-placental blood flow; however, smoking prior to the FHR recording may alter the FHR reactivity.     

Acute effects of maternal smoking on human fetal heart function

M-mode echocardiography was used to evaluate fetal heart function following maternal smoking in 21 healthy smoking pregnant women between 24 and 39 weeks of uneventful gestation. Prior to smoking one cigarette (nicotine content 1.7 mg), a fetal M-mode echocardiographic examination was performed and repeated 5 and 10 min after maternal smoking. Maternal heart rate and systolic blood pressure increased 8.7% and 15.0%, respectively, immediately after smoking, while diastolic blood pressure remained unchanged. Fetal heart rate increased 4.3% and left ventricular diastolic and systolic diameters decreased 4.5% and 15.0%, respectively. No changes in right ventricular dimensions, ventricular ejection times, ventricular wall thickness or septal thickness were observed. Fractional shortening, mean velocity of fractional shortening, stroke volume and cardiac output of the left ventricle also remained unchanged subsequent to smoking. Thus, maternal smoking of one cigarette seems to elicit only a transitory acceleration in fetal heart rate without concomitant significant changes in fetal heart function.     

Acute effects of maternal smoking on fetal heart beat intervals

The purpose of this study was to analyse the acute effects of maternal cigarette smoking on the fetal heart beat intervals and their variability during the last trimester of a normal gestation. The fetal heart beat intervals were monitored continuously by abdominal electrocardiography for 60 min before and 60 min after smoking in 10 pregnant women. The mean intervals, their long-term variability (SD) and short-term variability (standard deviation of interval differences (SDID], calculated for 30-sec periods, showed a steady state before smoking. During the control period, the mean beat interval was negatively correlated with daily cigarette consumption and the short-term variability was positively correlated with the maternal plasma nicotine level. After smoking, the mean beat interval and the short-term variability decreased transiently, the values of both these parameters being positively correlated with the maternal nicotine values before smoking. The acute response of fetal heart beat intervals and their variability to one cigarette is distinct but transient, and the results suggest that the effects are modified by the chronic smoking habits of the women.     

Acute effects of smoking on fetal heart-rate variability

Summary. Smoking a standard filter cigarette caused an acute decrease both in the interval index and the differential index of fetal heart-rate variability in eight healthy pregnant women at term. The maximum effect occurred 5–10 min after smoking and the indices returned to the presmoking level in 20 min. We suggest that smoking has a dual effect on the fetus: one being narcotic, leading to a lowered interval index, and the other hypoxic, leading to a lowered differential index.     

Acute effects of maternal cigarette smoking on fetal heart rate and fetal body movements felt by the mother.

Acute effects of maternal cigarette smoking on fetal heart rate (FHR) and fetal body movements felt by the mother (FM) were studied in 51 pregnant volunteers. Thirty four were chronic smokers (6 or more cigarettes per day, with an average of 14 cigarettes/day) and 17 were sporadic smokers (1 to 5 cigarettes per day, with an averaged of 3 cigarettes/day). In both groups the number of FM, fetal reactivity and short-term FHR variability decreased significantly in the 20 minutes following cigarette smoking; a sustained FHR rise of 10 or more beats/min was also found after the cigarette in more than 50% of the cases in the 2 groups. No statistically significant differences were found among the 2 groups when the post-cigarette data were compared. We conclude that maternal cigarette smoking produces important acute effects upon FM and FHR regardless the average daily number of cigarettes smoked by the mother.     

Doppler measurements of maternal and fetal blood flow

Data accumulated over the last decade suggest that Doppler flow velocity waveforms can be used to study both maternal and fetal circulation. Information obtained with this technique appears useful as a screen for both maternal and fetal risk, as an aid to understanding perinatal anatomy and physiology, and as an adjunct to standard means of fetal surveillance.     

Acute effects of maternal ethanol infusion on fetal cardiac performance

In adult animals and man, both acute and chronic ethanol intake is associated with depression of myocardial performance. Accordingly, the cardiac effects of maternal ethanol infusions, in a manner comparable to common obstetric practice for inhibition of premature labor, were evaluated in six chronically instrumented fetal sheep. Fetal and ewe arterial Po₂, Pco₂, and pH values remained within normal limits with infusion rates of 15 c.c. per kilogram of 10 per cent ethanol over two hours (blood ethanol = 110 mg. per cent) and 15 c.c. per kilogram over one hour (blood ethanol = 210 mg. per cent). Fetal instrument evaluation (for 14 to 30 days after operation) provided data concerning pressures and cardiac dimensions which allowed analysis of left ventricular performance. Ethanol produced a significant depression of the extent (p < 0.01) and velocity (p < 0.001) of left ventricular myocardial fiber shortening as well as in the mean rate of left ventricular circumferential fiber shortening (p < 0.01). These indices of cardiac contractility were depressed in the absence of changes in end diastolic diameter, left atrial pressure, and systemic arterial pressure. Thus, the practice of inhibition of premature labor with ethanol might contribute to depressed myocardial performance in the neonatal period.     

Chronic effects of maternal smoking on pulse waves in the fetal aorta

Objective.?In order to evaluate the impact of maternal smoking on arterial stiffness in utero, pulse wave characteristics in the fetal aorta were investigated. A prospective clinical study was made of 34 smoking and 34 non-smoking healthy volunteers with uncomplicated pregnancies at 31–40 weeks of gestation.

Methods.?The mechanical properties of the fetal thoracic aorta were assessed by an ultrasonic phase-locking echo-tracking system. For each fetus with a smoking mother, a non-smoking control matched for gestational and maternal age was monitored. Women with later appearing pregnancy complications were excluded. Pulse wave velocity (PWV), maximum diameter in systole (Ds), end-diastolic diameter (Dd), pulse amplitude (ΔD), and maximum incremental velocity (MIV) in the fetal aorta were measured and analyzed in relation to maternal smoking and gestational age.

Results.?Results were computed on fetuses of 32 smokers and 30 non-smokers. PWV increased with gestational age in smokers (corr. coeff. 0.49, p < 0.006) but not in non-smokers (corr. coeff. ?0.12). MIV did not change in smokers (corr. coeff. ?0.15) but increased in non-smokers (corr. coeff. 0.40, p < 0.03). Differences in regression lines between the groups regarding PWV and MIV were significant (p < 0.02 for both).

Conclusions.?Maternal smoking seems to promote the stiffening of the fetal aorta during gestation.     

Chronic effects of maternal smoking on pulse waves in the fetal aorta.

OBJECTIVE: In order to evaluate the impact of maternal smoking on arterial stiffness in utero, pulse wave characteristics in the fetal aorta were investigated. A prospective clinical study was made of 34 smoking and 34 non-smoking healthy volunteers with uncomplicated pregnancies at 31-40 weeks of gestation. METHODS: The mechanical properties of the fetal thoracic aorta were assessed by an ultrasonic phase-locking echo-tracking system. For each fetus with a smoking mother, a non-smoking control matched for gestational and maternal age was monitored. Women with later appearing pregnancy complications were excluded. Pulse wave velocity (PWV), maximum diameter in systole (Ds), end-diastolic diameter (Dd), pulse amplitude (DeltaD), and maximum incremental velocity (MIV) in the fetal aorta were measured and analyzed in relation to maternal smoking and gestational age. RESULTS: Results were computed on fetuses of 32 smokers and 30 non-smokers. PWV increased with gestational age in smokers (corr. coeff. 0.49, p < 0.006) but not in non-smokers (corr. coeff. -0.12). MIV did not change in smokers (corr. coeff. -0.15) but increased in non-smokers (corr. coeff. 0.40, p < 0.03). Differences in regression lines between the groups regarding PWV and MIV were significant (p < 0.02 for both). CONCLUSIONS: Maternal smoking seems to promote the stiffening of the fetal aorta during gestation.     

The current status of maternal and fetal blood flow velocimetry

Significant progress has been achieved in regard to normative data for uteroplacental and fetal blood flow velocity and the factors which may affect these observations. Associations have been demonstrated between abnormal indices of maternal and fetal blood flow velocity and pregnancy-induced hypertension, fetal growth retardation, fetal blood gas measures, and intrapartum clinical fetal distress. However, in general, the predictive power is modest and no evidence has yet been provided to indicate that these measures can be used as a screening test in the general obstetric population. Continuing research is highly desirable. At the present time, the use of Doppler assessment of blood flow in pregnancy should be limited to the investigational setting.     

The effect of maternal oxygen administration on fetal and maternal blood flow values using Doppler ultrasonography.

Thirty-one pregnant women divided into three groups (AGA prepartum, SGA prepartum without distress, AGA in labor) were examined using Doppler ultrasonography before, during and after oxygen administration to mothers via a face mask. The aim of the study was to find out if there was any effect on the blood flow values in the fetal aorta, the umbilical artery, the fetal common carotid artery and the uterine arcuate arteries. The resistance index (RI) did not change in those vessels during maternal hyperoxygenation with one exception: in the group of SGA fetuses the RI in the fetal aorta increased significantly. Blood flow velocity and volume blood flow remained unchanged in the fetal aorta during oxygen administration.     

Effects of maternal oxygen administration on fetal oxygenation during reductions in umbilical blood flow in fetal lambs

In 11 chronically catheterized fetal lambs (123 +/- 6, mean +/- SD, days of gestation; term = 147 days), we measured fetal oxygen delivery and oxygen consumption before and during reductions in umbilical blood flow (Qumb). Qumb was reduced by inflation of a balloon occluder located just proximal to the origin of the common umbilical artery. Measurements were made while the unanesthetized maternal sheep received either room air or 100% oxygen to breathe. In oxygen-treated fetuses, oxygen concentrations in umbilical venous blood (Cuvo2) and arterial blood (Cao2) were increased over a wide range of Qumb when compared with those of room air-treated fetuses. Because of these responses, fetal oxygen delivery (Do2 = Qumb X Cuvo2) and oxygen consumption [Vo2 = Qumb(Cuvo2-Cao2)] were greater in oxygen-treated fetuses than in room air-treated fetuses during episodes of reduced Qumb. In oxygen-treated fetuses, Vo2 decreased from normal levels only when Qumb was less than or equal to 75 ml/min/kg of fetus, whereas in room air-treated fetuses Vo2 decreased at Qumb less than or equal to 150 ml/min/kg. Our data indicate that oxygen administration to the pregnant sheep increases oxygen delivery to the fetus during times of reduced umbilical perfusion and that this supplemental oxygen supply provides an oxygen reserve with which the fetus can maintain oxidative metabolism. These data may be relevant to those clinical conditions, such as umbilical cord compression in labor, that are associated with reductions in umbilical blood flow.     

Reexamining the effects of gestational age, fetal growth, and maternal smoking on neonatal mortality

BACKGROUND: Low birth weight (<2,500 g) is a strong predictor of infant mortality. Yet low birth weight, in isolation, is uninformative since it is comprised of two intertwined components: preterm delivery and reduced fetal growth. Through nonparametric logistic regression models, we examine the effects of gestational age, fetal growth, and maternal smoking on neonatal mortality. METHODS: We derived data on over 10 million singleton live births delivered at >/= 24 weeks from the 1998-2000 U.S. natality data files. Nonparametric multivariable logistic regression based on generalized additive models was used to examine neonatal mortality (deaths within the first 28 days) in relation to fetal growth (gestational age-specific standardized birth weight), gestational age, and number of cigarettes smoked per day. All analyses were further adjusted for the confounding effects due to maternal age and gravidity. RESULTS: The relationship between standardized birth weight and neonatal mortality is nonlinear; mortality is high at low z-score birth weights, drops precipitously with increasing z-score birth weight, and begins to flatten for heavier infants. Gestational age is also strongly associated with mortality, with patterns similar to those of z-score birth weight. Although the direct effect of smoking on neonatal mortality is weak, its effects (on mortality) appear to be largely mediated through reduced fetal growth and, to a lesser extent, through shortened gestation. In fact, the association between smoking and reduced fetal growth gets stronger as pregnancies approach term. CONCLUSIONS: Our study provides important insights regarding the combined effects of fetal growth, gestational age, and smoking on neonatal mortality. The findings suggest that the effect of maternal smoking on neonatal mortality is largely mediated through reduced fetal growth.     

The effects of ritodrine and magnesium sulfate on maternal and fetal Doppler blood flow patterns in women with preterm labor

Objective

To determine the effects of ritodrine and magnesium sulfate on maternal-fetal blood flows.

Study design

A total of 85 pregnant women between 26th and 36th weeks with preterm labor, and 83 healthy pregnant women were included. Patients in the study group were randomly assigned to receive either ritodrine (with the addition of verapamil) (n = 46) or magnesium sulfate (n = 39). Blood flow examinations on the umbilical artery (UA), middle cerebral artery (MCA), bilateral uterine arteries (Ut.A) and ductus venosus (DV) were performed before and 48 h after initiating therapy.

Results

UA pulsatility index (PI) significantly differed in women receiving tocolysis compared to controls after 48 h. DV PI increased in women receiving MgSO₄, whereas it decreased in the ritodrine and control groups. Ut.A values did not significantly change after 48 h in the groups.In women between the 26th and 32nd weeks, UA, MCA and DV PI did not significantly change after 48 h in the three groups. However, in women between the 32nd and 36th weeks UA and MCA PI significantly differed in the treatment groups compared to controls after 48 h. DV PI increased in women receiving MgSO₄, whereas it decreased in the ritodrine and control groups.

Conclusions

MgSO₄ and ritodrine affect blood flow patterns after 48 h in some maternal-fetal vessels. These effects on blood flow are particularly significant in women between 32nd and 36th weeks. The effects of both drugs on fetal and maternal Doppler flows seem similar, except the increased resistance to flow in DV in women receiving MgSO₄.     

The association between maternal smoking and fetal hydranencephaly

OBJECTIVE: To evaluate the relationship between maternal smoking and fetal congenital central nervous system malformations. METHODS: Retrospective review of all cases of fetal congenital malformations of the central nervous system (CNS) identified at or shortly after birth over a 10-year period (1986-1995) in a university teaching obstetric department. RESULTS: The total number of CNS abnormalities identified was 79, constituting 0.13% of all deliveries over the period (n = 59,392) and 4.7% of all congenital malformations (n = 1,678). The incidence of smoking mothers was 1.64% over the study period. Four babies had hydranencephaly, 3 of these mothers being smoking teenagers. The odds ratio of having a hydranencephalic fetus in smoking mothers compared to non-smokers was 56 (95% CI 7.41-427) in the group with CNS abnormalities, 136 (95% CI 14.5-1280) in the group including all congenital malformations, and 179 (95% CI 18.6-1719) in the group including all deliveries. CONCLUSION: Maternal smoking did not appear to increase the incidence of fetal congenital CNS abnormalities overall, but might be associated with particular vascular patterns of damage to the developing brain that could predispose to a hydranencephalic malformation.     

Impact of maternal cigarette smoking on fetal growth and body composition

OBJECTIVE: The aim of this study was to determine the impact of maternal cigarette smoking on the fetal accretion of fat and lean body mass. We hypothesized that maternal smoking would result in a reduction in the deposition of lean body mass. STUDY DESIGN: Longitudinal ultrasonographic examinations on 65 singleton fetuses without anomalies of smoking mothers were compared with 36 singleton fetuses without anomalies of nonsmoking mothers. A total of 214 ultrasonographic examinations were performed between 27 and 37 weeks' gestation. All subjects underwent at least 2 ultrasonographic examinations separated by 4 weeks. We compared the slopes of the growth curves for individual morphometric parameters including head circumference, femur length, abdominal circumference, thigh muscle area, thigh fat area, estimated fetal weight and percentage of thigh fat between groups. Analysis was performed with a repeated measures analysis of covariance. Potential covariates included prepregnancy body mass index (in kilograms per square meter), weight gain during pregnancy, maternal age, parity, and fetal sex recorded at birth. Demographic variables are expressed as mean +/- SD; fetal measurements are expressed as mean +/- SE. Both t tests and chi(2) analyses were used to compare groups with respect to demographic variables. P <.05 was accepted for significance. RESULTS: There were no significant differences between groups in maternal prepregnancy weight, maternal height, maternal prepregnancy body mass index, weight gain in pregnancy, parity, or fetal sex. Smokers were younger than nonsmokers (smokers, 23.7 +/- 6.0 years; nonsmokers, 31.8 +/- 6. 0 years; P <.0001), and neonatal weight was reduced among smokers (smokers, 3269 +/- 507 g; nonsmokers, 3519 +/- 411 g; P <.01). There were no differences in the growth rates of head circumference (P =. 79) and femur length (P =.67). Growth rates of abdominal circumference (smokers, 9.0 +/- 0.3 mm/wk; nonsmokers, 10.3 +/- 0.5 mm/wk; P =.01), estimated fetal weight (smokers, 171 +/- 5.4 g/wk; nonsmokers, 193 +/- 8.0 g/wk; P =.008), and muscle area (smokers, 64. 1 +/- 3.8 mm(2)/wk; nonsmokers, 76.4 +/- 5.6 mm(2)/wk; P =.03) were significantly reduced among smokers. There was a reduction in the rate of fat deposition in the thighs of fetuses of smoking mothers (smokers, 38.7 +/- 3.7 mm(2)/wk; nonsmokers, 54.6 +/- 5.4 mm(2)/wk; P =.004); however there was no absolute difference in the amount of fat measured in the thigh between 33 and 37 weeks' gestation. CONCLUSION: We detected reduced fetal growth that selectively affected abdominal circumference and peripheral muscle mass while not affecting head circumference and femur length in fetuses of smoking mothers. The effect of cigarette smoking on fetal fat deposition was less clear. Cigarette smoking appears to have a selective effect within lean body mass compartments, with affected compartments including peripheral fetal muscle. The findings of a reduction in abdominal circumference growth compared with control subjects in combination with no difference in subcutaneous fat content beyond 33 weeks' gestation are potentially explained by a reduction in fetal liver size that may result from maternal smoking.     

Uteroplacental blood flow index in intrauterine growth retardation of fetal or maternal origin

Summary. Uteroplacental blood flow index was determined in 30 women with intrauterine growth retardation (IUGR group) and in 26 women without fetal growth retardation (control group) during the last trimester of pregnancy. After 1 mCi (37 MBq) of indium-113m chloride had been injected intravenously the radiation was registered by a computer-linked scintillation camera positioned above the placenta during 10 s-intervals for 240 s. From the isotope accumulation curve a Uteroplacental blood flow index could be calculated for each patient. The median blood flow index in the IUGR group was less than half of that in the control group. In the IUGR group the index was as low in the six women who gave birth to infants with congenital malformations as in the other 24 women in whom fetal growth retardation was due to maternal factors.     

Effects of smoking on uteroplacental blood flow

The effects of nicotine consumption on uteroplacental blood flow were studied in 20 pregnant women by means of placental blood flow measurements using indium-113m-transferrin. Smokers were found to have a higher rate of poor perfusion patterns than subjects of a control group. In addition, the number of cigarettes smoked daily was significantly correlated with the placental perfusion type. The mean birth weight of infants born by smokers was 250 g lower than in the control group. The results suggest that smoking during pregnancy may compromise uteroplacental blood flow and thus result in poor fetal development.     

Circulatory changes in the fetal aorta after maternal smoking

The acute cardiovascular responses of the human fetus to maternal smoking of one cigarette were studied in 10 healthy pregnant women. Following maternal smoking, a significant increase was found in the nicotine concentration in maternal plasma accompanied by a significant increase in the fetal heart rate. The flow velocity was recorded in the fetal descending aorta by combining real-time ultrasonography and the 2 MHz pulsed Doppler technique and the waveform of the maximum blood velocity was analysed. The duration of the acceleration part of the pulse cycle (start-to-peak time) remained unchanged during the study period. The least diastolic blood velocity increased significantly after smoking. The pulsatility index fell significantly during the first 5 min after smoking, probably as the consequence of fetal tachycardia, but was normal again at 10 min. The rising slope rose significantly within the first 10 to 20 min after the onset of smoking. The results indicate, that, following maternal smoking of one cigarette, fetal central circulation increases but peripheral resistance is unchanged.