Mary Penry

The effect of placental location on uterine artery flow velocity waveforms

We examined the effect of placental location with regard to flow velocity waveforms in the uterine arteries in 84 control and 28 hypertensive women during the third trimester of pregnancy. The ratio of systolic peak to end-diastolic frequency was obtained with a continuous-wave Doppler device and the placental location was determined by real-time ultrasonography. In both normal and hypertensive pregnancies with unilateral placental location the systolic/diastolic ratio of the ipsilateral uterine artery was significantly lower than the contralateral artery ratio [1.73 +/- 0.35 (systolic/diastolic ratio) versus 2.46 +/- 0.73, p less than 0.001, and 2.38 +/- 1.01 versus 4.04 +/- 1.77, p = 0.0012, respectively]. The physiologic and clinical significance of this finding is discussed.

Interrelationship and clinical significance of increasedresistance in the uterine arteries in patients with hypertension or preeclampsia or both

OBJECTIVES This study was designed to evaluate the clinical significance of the Doppler flow velocity waveform analysis of the two uterine arteries on an individual basis and in combination expressed as the mean uterine artery. STUDY DESIGN We evaluated uterine artery resistance by means of continuous wave Doppler ultrasonography in 123 pregnant women with chronic hypertension, preeclampsia, or both. The placental location was determined by real-time ultrasonography. Clinical outcomes were compared according to uterine artery abnormalities. The Doppler flow studies were not used in patient management. RESULTS In patients with unilateral placentas (n = 67) the placental uterine artery was found to be a better predictor of poor pregnancy outcome than the nonplacental artery and the mean of the two arteries. There was a strong degree of correlation between abnormal nonplacental uterine artery and abnormal mean of uterine artery (r = 0.75, p less than 0.001), and there was a moderate degree of correlation between abnormal placental uterine artery and abnormal mean uterine artery (r = 0.46, p less than 0.001). Uterine artery discordance (left-right uterine artery systolic/diastolic ratio) was mostly the result of an abnormal nonplacental uterine artery (r = 0.74, p less than 0.0001) and not the result of an abnormal mean uterine artery (r = 0.44, p less than 0.003); the degree of discordance did not relate to pregnancy outcome. Unilateral placental location was associated with longer stays in neonatal intensive care units and more perinatal deaths. CONCLUSION Because of the differences between the two uterine arteries, we conclude that for proper interpretation of uterine artery flow velocity waveforms, the placental location should be known and each vessel analyzed individually.

Variable decelerations during nonstress tests are not a sign of fetal compromise

An examination of 908 fetal heart rate tests of 418 consecutive patients revealed brief variable decelerations in more than 50.7% of the patients. Although an association existed with nuchal cord location found at delivery, no association existed between these variable decelerations and fetal heart rate decelerations during labor, low Apgar scores at birth, or birth weight. We find no evidence to suggest that these brief variable decelerations are a sign of fetal compromise or an indication for obstetric intervention.

Fetal renal pulsed Doppler waveform in prolonged pregnancies

OBJECTIVE Our purpose was to determine Doppler waveforms of the fetal human renal artery in prolonged pregnancy in the presence or absence of oligohydramnios. STUDY DESIGN Fifty patients at or after 40 weeks were studied. Ultrasonography was performed to determine the amniotic fluid index by the four-quadrants technique. Two groups of patients were obtained on the basis of the amniotic fluid index. Group 1 had an amniotic fluid index > 5 (normal) (n = 33); group 2 had amniotic fluid index < or = 5 (oligohydramnios) (n = 17). Umbilical artery and fetal renal pulsed Doppler waveforms were determined and analyzed. The fetal renal artery systolic-to-diastolic ratio of the two groups was compared. RESULTS Fetuses with a low amniotic fluid index had a significantly higher ratio. A significant negative correlation coefficient between amniotic fluid index and fetal renal systolic/diastolic ratio was found (r = -0.435 and p < 0.01). CONCLUSIONS In prolonged pregnancies there is a significant relationship between the amniotic fluid index and the fetal renal systolic/diastolic ratio. In pregnancies associated with oligohydramnios the systolic/diastolic ratio is significantly higher than in those with normal amniotic fluid volume. These data suggest that intrarenal flow in prolonged pregnancies complicated with oligohydramnios is significantly different.

Effects of maternal administration of 3% carbon dioxide on umbilical artery and fetal renal and middle cerebral artery Doppler waveforms

OBJECTIVE The null hypothesis is that umbilical, middle cerebral, and renal artery pulsed Doppler velocity waveforms in the normal term fetus may be affected during short-term maternal inhalation of 3% carbon dioxide gas mixture. STUDY DESIGN Seventy-two observations were made on 14 term fetuses before and during maternal 3% carbon dioxide gas mixture inhalation. The umbilical, middle cerebral, and renal arteries of these fetuses were sampled with pulsed Doppler velocity waveforms and recorded on a strip chart at a preset speed of 50 mm/sec. Doppler waveforms were analyzed for differences in the systolic peak to end-diastolic velocity ratio for these three vascular beds. Peak flow velocity and time velocity integral were also analyzed for the cerebral and renal vascular beds. The data were analyzed with the paired t test. RESULTS A significant decrease in the systolic-to-diastolic-velocity ratio of the middle cerebral artery occurred with 3% carbon dioxide inhalation (p < 0.02). The other vascular beds had no demonstrable change. CONCLUSION Transient maternal breathing of 3% carbon dioxide gas mixture selectively causes a decrease in resistance in the fetal cerebral circulation.

Effect of placental laterality on uterine artery resistance and development of preeclampsia and intrauterine growth retardation

We studied 153 pregnant women with normal pregnancies and 147 women with complicated pregnancies (diabetes, hypertensive disorders, and intrauterine growth retardation) to evaluate the association of placental location and the development of preeclampsia, intrauterine growth retardation, and uterine artery resistance. The placental location was determined by real-time ultrasonography, and the uterine artery resistance was determined by continuous-wave Doppler flow velocity waveform analysis. In the presence of preeclampsia or intrauterine growth retardation, up to 75% of the patients had unilaterally located placentas and 25% central placentas, whereas in the absence of these two conditions only 51% of the patients had unilateral and 49% central placentas (p less than 0.02). In patients with unilateral placentas, the incidence of preeclampsia and intrauterine growth retardation was 2.8-fold and 2.7-fold greater than in patients with central placentas (p less than 0.03 and p less than 0.01). Among all patients unilateral placental location was more likely to be associated with abnormal artery flow velocity waveforms than central placental location (p less than 0.001). We conclude that unilateral placental location may predispose to the development of preeclampsia and intrauterine growth retardation by its effect on uterine artery resistance.