Arteries In Normal Pregnancies Research Articles

Fetal superior mesenteric artery blood flow velocimetry in normal and high-risk pregnancy.

To record blood flow velocimetry in the fetal superior mesenteric artery in normal pregnancy and to evaluate if blood flow recordings in the vessel might predict adverse outcome in high-risk pregnancy. The fetal superior mesenteric artery blood velocimetry was recorded in a cross sectional manner in 75 normal pregnancies between 27 and 41 weeks of gestation. Reference curves were performed for pulsatility and resistance indices. The superior mesenteric artery was also located in 48 singleton pregnancies complicated by pregnancy-induced hypertension and/or intra-uterine growth retardation. Middle cerebral artery, umbilical artery and vein and uterine artery velocimetry were also recorded. Superior mesenteric artery PI and RI values expressed an increase in resistance to blood flow with gestational age after 32 weeks of gestation. In all except eight high-risk pregnancies the fetal mesenteric artery PI values were within normal range. Among the pregnancies with absent or reversed blood flow in the umbilical artery, all had abnormal mesenteric artery pulsatility index (PI) (> 97.5th percentiles), one fetus died intrauterine and two others died after delivery due to prematurity, growth retardation and necrotizing enterocolitis. In the remaining fetuses with increased mesenteric artery PI, necrotizing enterocolitis was diagnosed in three cases. Increased vascular resistance in the mesenteric artery might be a late sign of fetal circulation redistribution and frequently related to necrotizing enterocolitis in the newborn.

Ultrasonic fetal and placental tissue characterization and the role of Doppler ultrasound in lung maturity

Background: The aim of this study is to confirm the relationship between the gestational age and quantitative assessment of ultrasonic signs of placental tissue, fetal lungs and liver tissue and to correlate Doppler parameters from main stems of the pulmonary arteries for determining fetal lung maturity in normal pregnancy and pregnancy with pre‐eclampsia and diabetes.Methods: The placenta, fetal lungs and fetal liver in 300 normal pregnancies, 100 pre‐eclamptic pregnancies and 100 diabetic pregnancy were examined by ultrasound at 30–41 weeks of gestation. The coefficients of variation (the standard deviation divided by the mean value) were used to characterize the tissue in different groups during pregnancy. Doppler velocimetry was performed in the main stems of pulmonary arteries in normal pregnancies and pregnancies with pre‐eclampsia and diabetes.Results: The coefficients of variation in mature fetuses were greater than 29% for placentas in vivo, greater than 34% for placentas in vitro, greater than 28% for liver tissue and greater than 30% for lung tissue. Placental, lung and liver tissue of diabetic pregnancy tended to have lower coefficients of variation throughout their pregnancies. We found in mature fetuses mean peak systolic velocity higher than 40 cm/s and PI lower than 3.00. In mature fetuses with pre‐eclampsia, we found higher mean peak systolic velocity in compared with normotensive patients.Conclusions: The coefficient of variation values for placentas in vivo and in vitro, and fetal lungs and liver increase during pregnancy in normal and pre‐eclamptic patients with increasing gestational age and decrease in diabetic patients.

P104 Ultrasonic fetal and placental tissue characterization and the role of Doppler ultrasound in lung maturity

ObjectivesThe aim of this study is to known the relationship between the gestational age and quantitative assessment of ultrasonic signs of placental tissue, fetal lungs and liver tissue and to correlate Doppler parameters from main stems of the pulmonary arteries for determining fetal lung maturity in normal pregnancy and pregnancy with preeclampsia and diabetes.MethodThe placenta, fetal lungs and fetal liver in 300 normal pregnancies, 100 preeclamptic pregnancies and 100 diabetic pregnancy were examined by ultrasound at 30–41 weeks of gestation. The coefficients of variation (the standard deviation divided by the mean value) were used to characterise the tissue in different groups during pregnancy. Doppler velocimetry was performed in the main stems of pulmonary arteries in normal pregnancies and pregnancies with preeclampsia and diabetes.ResultsThe coefficients of variation in mature foetuses were greater than 29% for placentas in‐vivo, greater than 34% for placentas in‐vitro, greater than 28% for liver tissue and greater than 30% for lung tissue. Placental, lung and liver tissue of diabetic pregnancy tended to have lower coefficients of variation throughout their pregnancies. We found in mature foetuses mean peak systolic velocity higher than 40 cm/sec. and PI lower than 3,00. In mature foetuses with preeclampsia we found higher mean peak systolic velocity in comparing with normotensive patients.ConclusionThe coefficient of variation values for placentas in‐vivo and in‐vitro, and fetal lungs and liver increase during pregnancy in normal and preeclamptic patients with increasing gestational age and decrease in diabetic patients.

Doppler pulsatility index of the fetal renal artery in normal pregnancies — a prospective study

Doppler pulsatility index of the fetal renal artery in normal pregnancies — a prospective study

Bradykinin-mediated relaxation of isolated maternal resistance arteries in normal pregnancy and preeclampsia

OBJECTIVE: The aim of the study was to investigate bradykinin-mediated vasodilator function in small arteries from normotensive pregnant and nonpregnant women and from women with preeclampsia. STUDY DESIGN: Small subcutaneous arteries (approximately 250 μm luminal diameter) were dissected from biopsy specimens obtained at cesarean section from 24 normotensive pregnant women and 6 women with preeclampsia and during abdominal surgery in 15 nonpregnant women. Vascular function was assessed after arteries were mounted on a small vessel myograph. RESULTS: Preconstricted arteries from normotensive pregnant women demonstrated enhanced relaxation to bradykinin compared with those from nonpregnant women ( p < 0.05), whereas arteries from women with preeclampsia showed blunted responses compared with those from normotensive pregnant women ( p < 0.01). Relaxation in all groups was attenuated in the presence of the nitric oxide synthase inhibitor N ω -nitro- l-arginine so that it became similar in the three groups. Indomethacin had a small but significant inhibitory effect on bradykinin-induced relaxation, but this component of relaxation was no different among groups. Sensitivity of arteries to norepinephrine and sodium nitroprusside showed no significant differences in the three groups of women. CONCLUSION: This study provides evidence for an increase in bradykinin-mediated nitric oxide synthesis from the vascular endothelium of small arteries from the peripheral circulation of normotensive pregnant women and a relative reduction in women with preeclampsia. In turn, these changes may contribute to vasodilation in normal pregnancy and elevation of the blood pressure in preeclampsia. (Am J Obstet Gynecol 1996;175:1668-74.)

Altered endothelium-dependant relaxation in myometrial but not systemic resistance arteries in normal pregnancy and in pre-eclampsia

Altered endothelium-dependant relaxation in myometrial but not systemic resistance arteries in normal pregnancy and in pre-eclampsia

Continuous wave Doppler velocimetry of the main‐stem uterine arteries: the transvaginal approach

The purpose of the study was (1) to establish the efficacy of the transvaginal approach for continuous wave Doppler velocimetry of the main-stem uterine arteries in normal pregnancy and (2) to provide reference values for the flow velocity waveform indices of the main-stem uterine arteries in normal pregnancy. In a cross-sectional study from 16 to 40 weeks of pregnancy, 201 healthy normal women were examined by transvaginal continuous wave Doppler, and flow velocity waveforms were obtained from the main branch of the uterine artery on both sides. Nomograms were compiled for the systolic: diastolic ratio, pulsatility index and resistance index. Values for all variables declined during the course of pregnancy until 22 weeks' gestation, and then remained stable to term. Intra- and interobserver variations were 5% and 8%, respectively, and the examination time was < 5 min. Flow velocity waveform indices declined during pregnancy, indicating a decrease of resistance in the uteroplacental circulation. Our results are comparable to those obtained transvaginally by pulsed wave Doppler, previously reported in the literature. The transvaginal approach for continuous wave Doppler velocimetry of the main-stem uterine arteries is a simple, quick, accurate, safe, cheap and highly reproducible method, and is therefore suitable for evaluating the uteroplacental circulation.

4 Immune aspects of pathology of the placental bed contributing to pregnancy pathology

Interest has recently focused on the role of the placental bed in the pathogenesis of a variety of pregnancy disorders. Considerable advances have been made in the understanding of the complex relationships between maternal and fetal trophoblast in the placental bed in normal pregnancy. Invasion of uterine spiral arteries by extravillous trophoblast effects the physiological changes required to accommodate increased blood flow to the fetoplacental unit. Control of trophoblast invasion may depend on intrinsic properties, such as production of proteolytic enzymes and expression of a non-classical class I MHC antigen, but maternal cells within decidua may also play a role. Leukocytes form a major component of human decidualized endometrium and in the first trimester consist of granulated lymphocytes, macrophages and T lymphocytes. Suggested roles for decidualized leukocytes include natural killer cell activity, cytokine secretion, antigen presentation and immunosuppression. Several pregnancy disorders, including pre-eclampsia and intrauterine growth retardation, may be due to abnormal maternofetal cellular relationships within the placental bed causing inadequate invasion of spiral arteries and acute atherosis. However, the role of immunological factors in the pathogenesis of these disorders is uncertain since deposition of immunoglobulins and complement has also been detected in spiral arteries in normal pregnancy. Placenta accreta may reflect undue invasiveness of trophoblast and immunohistochemical studies of subinvolution of uteroplacental arteries also suggest an abnormal maternofetal relationship in the placental bed. Although the in vivo role of decidual leukocytes is not known, studies of infertile endometrium have reported a deficiency of granulated lymphocytes, suggesting a possible role in early implantation and placentation. Granulated lymphocytes may also play a role in pregnancy loss. There have been considerable advances in understanding of the abnormal maternofetal relationships in the placental bed which can lead to pregnancy disorders. However, the aetiology and pathogenesis of the various clinical conditions is unlikely to be fully established until regulatory mechanisms in normal pregnancy are elucidated.

Placental bed spiral arteries in the hypertensive disorders of pregnancy

The investigation of the histology of the placental bed spiral arteries in normal pregnancy and in pregnancies complicated by hypertension, with or without proteinura. An observational study, based on women having caesarean sections for clinical reasons. 17 normal pregnant women, 43 with gestational hypertension, of whom 39 had proteinuria, 17 with chronic hypertension, of whom 6 had proteinuria, and 5 with unclassified hypertension. Placental bed biopsies obtained during caesarean section. Histological appearance of sections stained with haematoxylin and eosin PAS and Lendrum's MSB. Biopsies containing spiral arteries were obtained from 6 normotensive and 44 hypertensive women. Trophoblastic invasion was present in 5 of the 6 normotensive biopsies but absent in the majority of those with hypertension. Subintimal proliferation was seen in all the normotensive biopsies but in only 8 of 28 from those with gestational hypertension and proteinuria. Other features seen predominantly or only in the hypertensive biopsies, in order of frequency, were medial hyperplasia, fibrin deposits, acute atherosis, endothelial vacuolation and thrombosis. Absence of physiological changes may not be peculiar to preeclampsia but may be associated or even a result of various forms of hypertension in pregnancy. Spiral arteries show a spectrum of changes in hypertensive pregnancies that do not appear to bear a clear-cut relation to the clinical signs.

Continuous wave Doppler flow velocity waveforms from the umbilical artery in normal pregnancy

The objective was to establish a normal reference range of the indices of umbilical artery waveforms using continuous wave doppler ultrasound. A prospective longitudinal study was made of 85 uncomplicated singleton pregnancies between 16 and 40 weeks gestation (783 recordings). Pulsatility Index (P.I.), Resistance Index (R.I.) and A/B ratio were measured at each visit. The mothers all delivered normal healthy infants weighing more than the 10th centile for gestational age. All three indices have a positively skewed frequency distribution, a factor not generally appreciated until recently and the ranges are therefore described using non-parametric statistics. Placental resistance decreases as term approaches, the 50% PI at 16 weeks was 2.06, at 32 weeks was 1.08 and at 40 weeks was 0.85. The results show a comprehensive reference of normal values and provides a sound basis for the further study of abnormal pregnancy. It represents the largest published study of its type using continuous wave Doppler.

Mean blood velocities and flow impedance in the fetal descending thoracic aorta and common carotid artery in normal pregnancy

A linear array pulsed Doppler duplex scanner was used to establish reference ranges for mean blood velocities and flow impedance (Pulsatility Index = PI) in the descending thoracic aorta and in the common carotid artery from 70 fetuses in normal pregnancies at 17–42 weeks' gestation. The aortic velocity increased with gestation up to 32 weeks, then remained constant until term, when it decreased. In contrast, the velocity in the common carotid artery increased throughout pregnancy. The PI in the aorta remained constant throughout pregnancy, while in the common carotid artery it fell steeply after 32 weeks. These results suggest that with advancing gestation there is a redistribution of the fetal circulation with decreased impedance to flow to the fetal brain, presumably to compensate for the progressive decrease in fetal blood Po 2.

Immunofluorescent studies of the uteroplacental arteries in normal pregnancy.

Immunofluorescent studies were performed on placental bed biopsies from 27 normal pregnancies. Uteroplacental arteries were present in 26 of the 27 biopsies and all showed deposition of fibrin in relation to the fibrinoid layer within the vessel wall; 12 also showed deposition of C3. Interstitial fibrinoid deposits also stained positively with fibrin. There was no deposition of immunoglobulins within the arterial changes nor in association with intramural or interstitial trophoblast. This study indicates that fibrin is a significant contributor to the fibrinoid layer within the uteroplacental arteries, and suggests that the presence of bound C3 is due to the activation of the complement system by fibrinogenesis. There was no evidence that the humoral immune response was involved in the aetiology of the physiological changes in the uteroplacental arteries.

Hormonal studies in pregnancy: I. Total unconjugated estrogens in maternal peripheral vein, cord vein, and cord artery serum at delivery

The concentration of unconjugated total estrogens (primarily estrone, estradiol-17β, and estriol) were measured by rapid radioimmunoassay method in serum samples from maternal peripheral vein, cord vein, and cord artery in normal pregnancies at delivery. The serum concentration of total free estrogens found in cord vein was four to five times higher than in maternal peripheral vein and cord artery. Levels obtained in maternal peripheral vein, cord vein, and cord artery were 47.8 ± 1.8, 140.1 ± 8.57, 31.8 ± 2.15 ng. per millilitre (± standard error of the mean), respectively. These values are compared with those reported by others.