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.

Placental abruption and perinatal death.

Studies of risk factors for abruptio placentae (AP) are partly conflicting and studies of risk factors for perinatal death in these pregnancies are scarce. Using the population-based Swedish Birth Registry from 1987 to 1993, we were able to study these risks in 795,459 singleton pregnancies. Logistic regression analysis was used to estimate odds ratios (OR) for risk of AP and risk of perinatal death in pregnancies with and without AP.

Impaired endothelial function and increased carotid stiffness in 9-year-old children with low birthweight.

Background: Low birthweight (LBW) has been associated with an increased incidence of adult cardiovascular disease. Endothelial dysfunction and loss of arterial elasticity are early markers of hypertension and atherosclerosis. We studied the prevalence of these markers in 44 healthy, prepubertal (age 9+/-1.

Mechanical Properties of Large Arteries in Mother and Fetus during Normal and Diabetic Pregnancy.

> Objective: To assess the influence of diabetes mellitus on the mechanical wall properties of large maternal and fetal arteries in pregnant women. Methods: Prospective serial monitoring of arterial wall characteristics, using ultrasonic phase-locked tracking of vessel diameters and oscillometric brachial blood pressure measurements. Ten pregnant women with insulin-dependent diabetes mellitus and 15 with gestational diabetes were studied and compared with 20 women in uncomplicated gestation.

Increased large arterial stiffness and impaired acetylcholine induced skin vasodilatation in women with previous gestational diabetes mellitus.

Objective: Gestational diabetes is associated with increased risk of developing noninsulin-dependent diabetes (NIDDM) later in life. By the time that a diagnosis of NIDDM is established, functional disturbances in the vascular system may be observed. This study was planned to assess macro- and microvascular function in nonpregnant women without signs of diabetes two to four years after a pregnancy complicated with gestational diabetes.

Dynamic properties of the aorta and of the foot microcirculation in adolescents with diabetes mellitus.

To evaluate vascular function in diabetic subjects, we studied both the stiffness of the abdominal aorta and the foot microvascular reactivity in 22 diabetic adolescents and 18 controls. The aortic stiffness was significantly higher in diabetic females, but not in males, as compared to age- and gender-matched controls (p < 0.05).

Dependence of aortic pulse wave assessments on behavioural state in normal term fetus.

To investigate any influence of behavioural states on the pulse waves in the descending aorta, 21 human fetuses were studied in utero in uncomplicated gestation at the age of 36-41 weeks. The fetal behavioural states were identified using two real-time scanners and one cardiotocograph. The aortic waveform data and pulse wave velocity (PWV) were recorded by means of two double phase-locking echo-trackers.

Effects of hypoglycaemia on fetal heart activity and umbilical artery Doppler velocity waveforms in pregnant women with insulin-dependent diabetes mellitus.

Objective: To study the effect of induced hypoglycaemia on fetal wellbeing as indicated by fetal heart rate and umbilical artery flow velocity waveforms.

Design: A prospective experimental investigation.

Setting: High risk pregnancy unit and diabetes research unit at Karolinska Institutet, Danderyd Hospital, a university affiliated hospital.

Increased stiffness of the aorta in children and adolescents with insulin-dependent diabetes mellitus.

An ultrasonic system fitted with echo-tracking circuits was used to investigate the mechanical properties of the descending aorta in children and adolescents with insulin-dependent diabetes (IDDM). Seventy-six children and adolescents (aged 5-20 years) with uncomplicated diabetes and 75 age- and gender-matched healthy controls were examined. All subjects were normotensive.

Effects of hydralazine on placental and renal circulation in pre-eclampsia.

Background: Although hydralazine has been the drug of choice for treating pregnancy-induced hypertension for some time owing to its effect on peripheral vascular tonus, its effects on utero- and feto-placental circulation are less well understood.

Methods: To evaluate the effect of hydralazine on placental circulation in cases of pre-eclampsia, Doppler ultrasonography was used to record blood velocity in the arcuate and umbilical arteries in 12 pregnancies complicated by pre-eclampsia, blood velocity in the maternal renal artery also being examined. The gravidae underwent Doppler ultrasonography after 24 hours bedrest in hospital (baseline values), and again 24 and 72 hours after starting oral hydralazine treatment at doses of 50 mg twice daily.

Low-dose aspirin to pregnant women: single dose pharmacokinetics and influence of short term treatment on bleeding time.

Single dose pharmacokinetics of 75 mg aspirin was investigated in two groups of ten women with clinically normal pregnancies. Eleven non-pregnant subjects in the same age were controls. In group A, gestational age was 27-30 completed weeks, and in group B, 36-39 weeks.

An ultrasonic system for diameter pulse tracking in arteries: problems and pitfalls.

Non-invasive ultrasonic techniques for measuring the mechanical behaviour of large arteries have a potential clinical application for physiological studies of the circulation and early detection of degenerative arterial disorders. A newly developed system for such purposes, comprising two double-echo trackers with zero-crossing phase-locked circuits and interfacing a B-mode real-time scanner, has been introduced for on-line recording of the diameter in a selected aortic segment. The aim of this report is to draw attention to the limitations of the technique in order to avoid misinterpretation of results.

Fetal aortic diameter pulse wave response to changes in maternal position after membrane rupture.

An ultrasonic phase-locked echo-tracking system was used in order to study human fetal hemodynamics in relation to maternal postural changes after membrane rupture. Diameter pulse waves were recorded in the descending aorta of 17 fetuses presenting by the vertex in normal singleton pregnancies, with the mother in three different positions. The first measurements were made with the mother in the slightly left lateral recumbent (horizontal), then upon transition to the upright (70 degrees), and finally upon return to the horizontal.

Aortic diameter pulse waves and blood flow velocity in the small, for gestational age, fetus.

An ultrasound phase-locked, echo-tracking system was used for noninvasive measurements of pulsatile diameter changes in the descending aorta of 60 small, for gestational age (SGA), fetuses and of 60 fetuses appropriate for gestational age (AGA). Pulsed Doppler ultrasound was used for the recording of blood flow velocity in the aorta and in the umbilical artery of the SGA fetuses. In the SGA fetuses, a weight-related higher end-diastolic diameter and a lower relative pulse amplitude suggest that diastolic blood pressure was increased; a less steep rise of the initial ascending part of the pulse wave and a lower relative pulse amplitude suggest that the absolute stroke volume was decreased.

Blood flow velocity and pulsatile diameter changes in the fetal descending aorta: a longitudinal study.

Blood flow velocity and pulsatile diameter changes in the fetal descending aorta were measured subsequently with pulsed Doppler ultrasonography and phase-locked echo-tracking technique, respectively. Blood flow velocity and pulse-wave curves with equal beat-to-beat intervals were synchronized by external fetal electrocardiogram. The systolic increase in blood flow velocity and in vessel diameter started simultaneously.

Analysis of components of fetal breathing cycles.

The duration of the inspiratory phase (Ti) and the expiratory phase (Te) together with the relative amplitude (Amp) of successive breathing movements of the chest wall or abdominal wall were measured by real-time ultrasound in 12 fetuses of normal gestation. The observations were performed at 33-39 gestational weeks. The distributions of Ti, Te, the duration of the breathing cycle (Ttot), Amp and the ratios Amp/Ti and Ti/Te were all considerably skewed.

Derivation of haemodynamic information from ultrasonic recordings of aortic diameter changes.

An ultrasound phase-locked echo-tracking system was used for noninvasive measurements of diameter changes in the upper abdominal aorta of the anaesthetised cat. Comparisons were made between the noninvasively recorded diameter changes and central haemodynamic variables measured with inserted catheters and transducers. It was found that noninvasive observations of aortic diameter changes give reliable information on the direction and relative magnitude of the blood pressure change both in systole and in diastole.

Low birth weight and risk of high blood pressure in adulthood.

Hospital birth records were sought for 104 men from a pool of male army conscripts with "normal" or "high" blood pressure when measured at 28 years of age. Of 77 men whose birth weight and date of the mother's last menstrual period before the pregnancy could be found, 25 had a resting diastolic blood pressure of greater than or equal to 90 mm Hg. In 11 of these compared with nine of the 52 men with normal diastolic pressures their birth weights in relation to gestational age had been below the mean and 1 SD of a comparable Swedish population.

Cardiovascular dynamics in relation to presentation and postural changes in normal fetuses.

The role of fetal cardiovascular function in the reduced intrauterine growth rate of breech pregnancy was studied in fetuses with different presentations. Hemodynamic responses to postural changes were also investigated in fetuses in horizontal and vertical positions. Thirty-one normal pregnancies, with 15 fetuses presenting by the breech and 16 fetuses by the vertex, were included in the study.

Interdependence of pulse wave variables in the human fetal aorta.

The problem of inferring the state of fetal circulation from diameter pulse waves in the descending aorta was studied with the aid of statistical methods in 12 fetuses in late uncomplicated gestation. By means of a phase-locked, echo-tracking ultrasound technique, aorta diameter-time waveforms and pulse propagation velocities were measured. In a factor analysis, three independent factors explained 75% of the total variance of variables in the waveforms.

The effect of carbon dioxide inhalation on phase characteristics of breathing movements in healthy newborn infants.

Chest wall distortion (inward motion of the rib cage on inspiration) has been found recently to reduce the tidal volume during active sleep in the neonatal period. To determine some of the factors that relate to the chest wall distortion and the decreased tidal volume seen in active sleep, a quantification of the phase differences between the movements of the chest wall and those of the abdominal wall, and of the relation of their phase differences to tidal volume was performed on data obtained before and during carbon dioxide stimulation in 15 newborn infants sleeping in the prone position. In quiet sleep, the breathing movements were congruent and regular, and the tidal volume and the mean inspiratory flow increased during carbon dioxide stimulation.

Incidence and recurrence rate of abruptio placentae in Sweden.

It is desirable to identify those pregnancies that run an increased risk of abruptio placentae, as this disorder still is associated with a high perinatal mortality. Data were collected from the Swedish nationwide birth registry system on all 894,619 births in Sweden in the period 1973 to 1981. The overall incidence of abruptio placentae was 0.

Pulse wave recording--development of a method for investigating foetal circulation in utero.

The need to investigate the elastic properties of arterial vessels 'in situ' for the early recognition of degenerative disorders in arteries has long been apparent. Volume pulses in defined segments of arteries can be evaluated for this purpose, and the present paper contains a survey of earlier attempts to quantify volume pulses by means of ultrasound. A presentation is given of a recently developed digital system, comprising a phase-locked echo tracker, capable of monitoring non-invasively the diameter and its pulsatile changes of a selected artery along two chosen image lines of a linear array ultrasound scanner.