Maternal angiotensin sensitivity and fetal Doppler umbilical artery flow waveforms

Article Abstract:

Abnormalities of blood flow through the fetal umbilical artery, which carries blood from fetus to placenta, are present in as many as three fourths of the infants born small for their gestational age and in fetuses at risk for breathing and other complications after birth. These blood flow aberrations appear as abnormalities of flow velocity waveform (FVW) on ultrasound examination. It is possible that abnormalities of the placental circulation such as those that occur with high blood pressure (hypertension) increase the resistance to blood flow in the umbilical artery, causing abnormal FVWs. It is also possible that FVW abnormalities develop independently and may precede vascular problems in the placenta. To learn more about this issue, 36 pregnant women were studied using Doppler ultrasonography on at least two occasions. The women were then observed to determine the outcome of pregnancy. The subjects' sensitivity to the infusion of angiotensin, a substance that can induce hypertension, was measured to evaluate the relationship between maternal blood pressure and FVWs. Eighteen women had a positive angiotensin pressor response (a diastolic blood pressure increase of more than 20 points) and formed the positive group; the remaining 18 women formed the negative group. Those in the positive group delivered earlier and had smaller infants than those in the negative group. Only one woman in the positive group experienced a spontaneous onset of labor, compared with seven in the negative group. Moreover, fetal distress occurred more often in the positive group. Fifteen of 16 pregnancies that continued in the negative group showed a normal decrease in the ratio of systolic to diastolic pressure (a change that reflects normal development of the blood vessels in the placenta), compared with only 6 of 16 pregnancies in the positive group. The results indicate that women at high risk for placental insufficiency can be identified using the angiotensin infusion sensitivity test. The physiological consequences of vascular abnormalities in the placenta are discussed. The recommendation is made that women with certain results on FVW analysis be given aspirin, which may affect the development of the placental vasculature, for the remainder of their pregnancies. (Consumer Summary produced by Reliance Medical Information, Inc.)

Blood flow, Risk factors, Angiotensin, Angiotensins, Placental diseases, Placenta diseases, Prenatal ultrasonography, Ultrasonics in obstetrics, Umbilical arteries

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Umbilical artery velocity waveforms: poor association with small-for-gestational-age babies

Article Abstract:

Abnormal growth of the fetus during pregnancy, or intrauterine growth retardation (IUGR), can complicate pregnancy, labor and delivery, and is associated with a poor fetal outcome. IUGR can be caused by a compromised blood supply to the fetus or it can simply represent adequate growth of a genetically small infant. Patterns produced by Doppler ultrasound can be used to assess the blood flow in the fetal arteries. To see if Doppler ultrasound can identify fetuses who are growth retarded, 205 high risk fetuses suspected of being small for gestational age (SGA, smaller than 90 percent of the fetuses of the same fetal age) were studied. The ratio of the peak systolic to end diastolic frequency (A/B ratio), a pattern produced by the Doppler ultrasound waveform, was used to distinguish normal from abnormal. Of the 205 pregnancies studied, 56 had abnormal Doppler waveform patterns, 34 of whom (61 percent) were born SGA. Of the 82 fetuses born SGA (40 percent), 48 had normal Doppler findings (59 percent) and 34 had abnormal findings (41 percent). The ponderal index, a measurement of body mass, and the standard deviation above or below the mean were used as an alternative measure of growth. On the basis of these alternative indices, the infants born with abnormal Doppler results were smaller than the infants born with normal Doppler results. Although the Doppler results can identify groups of smaller infants, its ability to identify individual growth retarded pregnancies was limited. (Consumer Summary produced by Reliance Medical Information, Inc.)

Diagnosis, Testing, Birth weight, Low, Low birth weight, Gestational age, Doppler ultrasonography

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Fetal growth achievement and neurodevelopmental disability

Article Abstract:

A complication of pregnancy such as maternal high blood pressure, hemorrhage, or premature delivery can be associated with a poor fetal outcome. A poor pregnancy history commonly results in children born with impaired neurological development. The relationship between complications of pregnancy and poor neurological development was studied by comparing the records of 287 disabled children with 600 normally developed children. The average birth weight of the disabled children was 6.9 pounds (3138 grams) compared with 7.2 pounds (3280 grams) in normally developed children. When adjustments were made for factors which could potentially obscure results, such as maternal age, height, weight, previous pregnancies, infant sex, fetal age and birth weight for fetal age, the children with disabilities were smaller for their fetal age than normally developed children. The risk for small-for-gestational-age (SGA) after a complication of pregnancy was 6.6 compared with 1.4 in pregnancies without a complication. The risk of neurological impairment was also higher in SGA infants. There was a stronger association between prenatal complications and disability than between prenatal complications and retarded growth alone. It was concluded that prenatal complications can slow down fetal growth enough to impair the development of the fetal brain. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Causes of, Developmentally disabled, Developmentally disabled persons, Prenatal influences, Brain-damaged children

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