Uterine Artery Flow Research Articles

Effect of parity on second-trimester uterine artery Doppler flow velocity and waveforms.

To investigate the relationship between second-trimester uterine artery Doppler findings and parity in a large pregnant population. Uterine artery Doppler studies were performed in all singleton pregnancies at 18-23 weeks of gestation. The mean uterine artery resistance index and the presence or absence of protodiastolic notches were recorded. Two groups were identified: pregnancies not complicated by pre-eclampsia, and pregnancies with pre-eclampsia severe enough to require delivery at or before 32 weeks of gestation. In the 4132 pregnancies uncomplicated by pre-eclampsia, parity was shown to be an independent predictor for both mean uterine artery resistance index (beta = 0.073, P < 0.001) and the presence of bilateral protodiastolic notches (odds ratio = 0.67; 95% CI, 0.45-0.98). In the 17 pregnancies complicated with severe pre-eclampsia, uterine artery Doppler indices showed a trend towards being better predictors of disease in nulliparous compared with parous women. Parity has a significant effect on the resistance index and the prevalence of protodiastolic notching in the uterine artery flow waveforms. This difference is clinically noticeable in its effect on notching. These findings suggest that some permanent modification may persist in the maternal vessels after a successful pregnancy, altering their impedance in subsequent pregnancies.

Transvaginal Doppler ultrasound with color flow imaging in luteal phase defect

Luteal phase defect (LPD) has been implicated as a cause of early infertility and abortion in 3.4– 34% of infertile women w1x. We hypothesize that LPD is due to decreased vascularization of the corpus luteum resulting in reduced delivery of steroid precursors to the ovary or inadequate progesterone production. This could be detected by study of ovarian and uterine artery flow dynamics. Fifty women with unexplained infertility at high risk for LPD i.e. age )35 years (mean 35.20.09) and recurrent abortions, were submitted to transvaginal ultrasound for evidence of ovulation and color Doppler for uterine and ovarian artery flow dynamics in various phases of a single menstrual cycle (early follicular, day 6–8; late follicular, day 9–12; early luteal, day of ovulation q2–4; mid-luteal, day 5–6; late luteal, day 9–11) daily until ovulation and thereafter every other day and were compared with 50 fertile women (18–35 years, mean 32.43) having normal menstrual cycles and reproductive history but without any uterineyadnexal surgery. Informed consent was given by all. A definite diagnosis of

The effect of exogenous estradiol benzoate and altrenogest on uterine and ovarian blood flow during the estrous cycle in mares

In recent years, a positive relationship between genital perfusion and fertility has been established; in species other than horses, uterine and ovarian perfusion was improved by exogenous estrogen but impaired by exogenous progestin. The goal of the present study was to investigate the effect of exogenous estrogen and progestin on uterine and ovarian blood flow in cycling mares. Five Trotter mares were examined daily during three estrous cycles. Mares were given no treatment, altrenogest (0.044 mg/kg BW) orally from Day 0 (ovulation) to Day 14 and estradiol benzoate (5 mg i.m.) on Days 0, 5, and 10, in three cycles, respectively. There was no difference ( P>0.05) in the length of untreated versus estrogen-treated cycles (22.8±1.3 days and 23.2±1.5 days, respectively), but cycle length was increased ( P<0.05) in progestin-treated cycles (26.0±1.2 days). To facilitate comparisons among cycles with different lengths, data from Days 0 to 15 (diestrus) and from Days −6 to −1 (estrus) were analyzed. Transrectal Doppler sonography was used to evaluate blood flow in both uterine arteries and in the ovarian artery ipsilateral to the preovulatory follicle during estrus and ipsilateral to the corpus luteum during diestrus. Blood flow was assessed semiquantitatively using the pulsatility index (PI); high PI values indicated high resistance and a low perfusion and vice versa. An immediate effect of treatments occurred only after the administration of estradiol benzoate on Day 0; uterine PI values decreased ( P<0.05) between Days 0 and 1 and estrogen-treated mares but increased ( P<0.05) at the corresponding time in untreated cycles. Mean PI values for the uterine and ovarian arteries during both diestrus and estrus were higher ( P<0.05) in estrogen-treated versus untreated mares. Furthermore, mean uterine PI values during diestrus and estrus were higher ( P<0.05) in altrenogest-treated versus untreated mares. Neither estrogen nor altrenogest treatments had a significant immediate effect on ovarian PI values. Compared to untreated cycles, mean ovarian PI values were elevated ( P<0.05) only in the estrus following altrenogest administration. In conclusion, exogenous estrogen and progestin both decreased genital perfusion in cycling mares.

1168 The phenomenon of fatigue in young people

Objectives: To evaluate the effects of sequential continuous hormone replacement therapy (HRT) on myoma size and on pulsatility index (PI) of uterine arteries and to verify the correlation between uterine artery flow impedance and the growth rate of myoma in women receiving HRT. Methods: In a prospective 1-year study 60 postmenopausal women were enrolled into three study-groups to receive continuous transdermal 17β-oestradiol 0.05 mg/day plus nomegestrolo acetate 5 mg/day sequentially added: 20 patients (group A) unaffected by uterine myomas, 20 patients (group B) with single asymptomatic myoma <3 cm/14 cm3, 20 patients (group C) with single asymptomatic myoma >3 cm/14 cm3. The changes in myoma volume and in PI were assessed by means of transvaginal ultrasonographic scan every 3 months. The patients with myoma were divided into two subgroups: quiescent myoma (B1, C1) and growing myoma (B2, C2). Results: No significant increase of uterine fibroids volume was found after 1-year HRT (24.14±20.02→28.81±30.02 cm3). Six out of eight myomas growing during HRT belonged to group C. The uterine artery basal PI value of group A was significantly higher (P<0.01) than the corresponding PI in group B and C. At 3 months follow-up, uterine artery PI was significantly higher (P<0.01) than the basal value in both group B (1.70±0.22→1.88±0.16) and C (1.59±0.28→1.92±0.21). The baseline PI values in group B1 and C1 were significantly higher than the baseline values observed in group B2 and C2 (1.76±0.17 vs. 1.32±0.02, 1.76±0.16 vs. 1.24±0.08) and significantly lower than those observed in group A (2.39±0.47). After 3 months of HRT, the PI values were not significantly higher than the baseline values in groups B1 and C2 (1.76±0.17→1.90±0.17; 1.24±0.08→1.74±0.16), while they were significantly higher in group C1 (1.76±0.16→2.01±0.17). Conclusions: Sequential continuous HRT does not increase the volume of the uterine myoma. The findings of very low resistance index in the uterine arteries of women with growing myoma may indicate the risk of growth of the neoplasia during HRT. The assessment of PI in the uterine arteries could be helpful in predicting the growth rate of the myomas before starting HRT.

Differential Blood Flow in Uterine, Ophthalmic, and Brachial Arteries of Preeclamptic Women

Differential Blood Flow in Uterine, Ophthalmic, and Brachial Arteries of Preeclamptic Women

Misoprostol administration in first-trimester pregnancies with embryonic demise reduces uterine arterial blood flow

Objectives: This study was designed to evaluate the effect of misoprostol on the blood flow in uterine arteries of pregnant women with first-trimester embryonic demise.Methods: Transvaginalultrasonographic Doppler examinations (resistance index, pulsatility index, systolic/diastolic ratio) of the uterine arteries in 61 pregnant women were performed before misoprostol administration and 90min later. Following baseline Doppler measurements, each woman received 200 μg misoprostol intravaginally and 200 μg misoprostol orally.Results and conclusion: All Doppler indices increased significantlyafter misoprostol administration (p < 0.0001), suggesting an increase in flow resistance.

Cardiopulmonary effects of xylazine and acepromazine in pregnant cows in late gestation.

To determine effects of sedation achieved by xylazine (XYL) or acepromazine (ACE) on cardiopulmonary function and uterine blood flow in cows in late gestation. 8 cows between 219 and 241 days of gestation. Doses of ACE (0.02 mg/kg) or XYL (0.04 mg/kg) were administered IV. Measurements were obtained to determine cardiopulmonary effects and oxygen delivery to the uterus. Heart rate was not significantly affected by administration of ACE, but it decreased markedly after administration of XYL. Uterine artery flow was decreased at all times by XYL and was always less than for ACE. Xylazine increased uterine vascular resistance through 30 minutes and caused reduced PaO2 and increased PaCO2 at all time periods. Acepromazine caused a 5% decrease in PaO2 only at 5 minutes. Xylazine reduced oxygen delivery by 59% at 5 minutes and 32% at 45 minutes. In contrast, ACE caused a nonsignificant reduction of oxygen delivery by 16% at 15 minutes and a return to baseline values by 45 minutes Xylazine markedly reduces flow and availability of oxygenated blood to the uterus, which may critically impair delivery of oxygen to the fetus at a stressful and important time of development or delivery. Acepromazine was associated with slight reductions of much shorter duration. When XYL is used to sedate pregnant cows, it could impose physiologic distress on the fetus and potentially increase fetal morbidity and mortality. When sedation of the dam is desirable, ACE could be an alternative to XYL.

Chronic hypoxia opposes pregnancy-induced increase in uterine artery vasodilator response to flow.

We tested the hypotheses that pregnancy increases the uterine artery (UA) vasodilator response to flow and that this increase is impaired under conditions of chronic hypoxia (30 days, simulated elevation 3,960 m). UA were isolated from 24 normoxic or chronically hypoxic midpregnant guinea pigs and studied with the use of pressure myography. Normoxic pregnancy increased UA flow vasodilator response and protected against a rise in wall shear stress (WSS). Chronic hypoxia opposed these effects, prompting vasoconstriction at high flow and increasing WSS above levels seen in normoxic pregnant UA. The nitric oxide synthase inhibitor N(G)-nitro-l-arginine (l-NNA) eliminated the pregnancy-associated increase in flow vasodilation in normoxic UA, suggesting that increased nitric oxide production was responsible. The considerable residual vasodilation after nitric oxide synthase and cyclooxygenase inhibition implicated endothelial-derived hyperpolarizing factor (EDHF) as an additional contributor to flow vasodilation. l-NNA increased flow vasodilation in UA from chronically hypoxic animals, suggesting that chronic hypoxia may have lowered EDHF or elevated peroxynitrite production. In conclusion, flow is an important physiological vasodilator for the acute and more chronic UA dimensional changes required to increase uteroplacental blood flow during normal pregnancy. Chronic hypoxia may be a mechanism that opposes the pregnancy-associated rise in UA flow vasodilation, thereby increasing the incidence of preeclampsia and intrauterine growth restriction at a high altitude.

Differential Blood Flow in Uterine, Ophthalmic, and Brachial Arteries of Preeclamptic Women

Differential Blood Flow in Uterine, Ophthalmic, and Brachial Arteries of Preeclamptic Women

Differential blood flow in uterine, ophthalmic, and brachial arteries of preeclamptic women

OBJECTIVE: To develop a method that employs noninvasive, pulsed Doppler ultrasonography combined with measurement of flow-mediated vasodilation to evaluate characteristic endothelial dysfunction in various degrees of preeclampsia. METHODS: Uterine, ophthalmic, and brachial arterial blood flow of 99 pregnant women (control group [ n = 32], non-preeclamptic intrauterine growth restriction group ( n = 15), mild preeclampsia group [ n = 25], and severe preeclampsia group [ n = 27]) were evaluated by pulsed Doppler ultrasound or flow-mediated vasodilation. RESULTS: Uterine, orbital, and brachial circulation were altered in preeclampsia, whereas no significant differences were observed between the non-preeclamptic intrauterine growth restriction and control groups. Pulsatility index in the uterine arteries of preeclamptic women with intrauterine growth restriction was approximately three-fold higher than that of normotensive women with or without intrauterine growth restriction. The peak ratio (defined to quantify characteristic flow velocity waveform) of the ophthalmic artery of hypertensive women was significantly higher than that of normotensive women. Flow-mediated vasodilation in the brachial artery of preeclamptic women with intrauterine growth restriction was significantly lower than that in preeclamptic women without intrauterine growth restriction. Among preeclamptic women, elevation of the resistance in the uterine artery and reduced flow-mediated vasodilation were closely correlated to intrauterine growth restriction, whereas the elevated peak ratio of the ophthalmic artery was dependent on hypertension, irrespective of the presence of intrauterine growth restriction. CONCLUSION: Ultrasound evaluation of uterine and orbital circulation and flow-mediated vasodilation of the brachial artery helps differentiate the degree and severity of preeclampsia.

Severity of symptoms in primary dysmenorrhea—a doppler study

Objective: Doppler findings in women with severe symptoms of primary dysmenorrhea include high impedance to blood flow in uterine arteries with a preserved cyclic pattern throughout the whole cycle. Doppler findings in women who present with mild symptoms of primary dysmenorrhea are not yet documented. The aim of this study was to investigate possible differences in Doppler findings among women with mild and severe primary dysmenorrhea. Study design: One hundred and fifty four women were examined with color Doppler ultrasound: 50 in the control group, 60 in the mild and 44 in the severe primary dysmenorrhea subgroup. We calculated resistance index in uterine arteries in these women on the first day of the cycle, in the follicular (days 9–12) and the luteal (days 20–23) phase of the cycle and used analysis of variance for comparing results. Results: The rate of visualization was 100% for uterine and arcuate arteries, 44–76% for the radial and 32–62% for spiral arteries, respectively. A significant difference in Doppler index values among the mild and severe dysmenorrheic group was observed in the luteal phase for the arcuate artery and in all the three measurement periods for the radial and spiral arteries. Conclusion: There is a difference in Doppler findings between women with mild and severe symptoms of primary dysmenorrhea.

Uterine Artery Embolisation for the Treatment of Symptomatic Fibroids in 114 Women: Reduction in Size of the Fibroids and Women’s Views of the Success of the Treatment

This investigation was conducted to evaluate the ability of uterine artery embolization to reduce the size of uterine fibroid tumors and to determine women's own assessment of the success of the procedure. Uterine embolization is a minimally invasive procedure involving insertion of a catheter into the uterine artery and embolization with polyvinyl alcohol particles (Boston Scientific Ltd, Cork, Ireland) 355 to 500 μm in diameter. Occlusion or reduction of flow in both uterine arteries is achieved with fiber platinum coils inserted into the artery (Boston Scientific Ltd). For this study, magnetic resonance imaging (MRI) scans were taken before and 6 months after embolization to assess the change in the uterine fibroid. T 2 weighted sequences on MRI were taken of all study subjects. T 1 weighted sequence scans were also taken of some patients but proved not to provide useful information. Study subjects were 114 unselected consecutive women who had undergone MRI 6 months after an embolization procedure. At 3, 6, 12, 18, and 24 months after the procedure, patients were asked to complete a questionnaire about their own assessment of the success of embolization. The 114 women were a mean of 42 years of age and had a total of 165 uterine fibroids, including 73 women with 1 to 3 fibroids, 14 with 4 to 10 fibroids, and 27 women with 11 or more fibroids. One hundred one of the tumors were less than 8.5 cm in diameter, and 64 were 8.5 cm or larger. After embolization, the total volume of the fibroids was reduced by a median of 58%. Ten women experienced complete destruction of their fibroids, and 5 had nearly total destruction (98% reduction in volume). The 64 women with large fibroids (>8.5 cm) had a median 50% reduction in tumor volume. There were three women whose fibroid tumors increased in volume after embolization. The women with interstitial (N = 38), submucous (N = 33), subserous (N = 30), or complex fibroid masses (N = 51) experienced a median reduction in tumor volume ranging from 63% to 52%. Pedunculated subserous fibroids (N = 7) had a median volume reduction of 38%, and pedunculated submucous tumors had a median 100% reduction. The results of the questionnaire showed that overall, 38% of the women had no further symptoms after uterine embolization, 53% reported an improvement in their symptoms, and 10% noticed no change or worsening of their symptoms. Women with smaller fibroid tumors were more likely and women with larger fibroids were less likely to experience a complete resolution of symptoms.

Uterine restoration by radiation sequelae regression with combined pentoxifylline-tocopherol: a phase II study

Objective: To determine whether combined pentoxifylline (PTX) and tocopherol (vitamin E) treatment can improve uterine radiation-induced sequelae, resulting in an improved embryo implantation rate. Design: Retrospective phase II clinical trial. Setting: Volunteers in an oocyte donation program in a public hospital. Patient(s): Six women aged 31 ± 4 years, who were irradiated 25 years previously for childhood cancer with 20 to 40 Gy including the pelvic area. Intervention(s): Four women had taken hormone replacement therapy for primary amenorrhea, and two had retained their natural cycle. Treatment consisted of at least 12 months of pentoxifylline at 800 mg/day combined with 1000 IU/day of tocopherol. Main Outcome Measure(s): Endometrial thickness, uterine volume, and uterine artery blood flow were assessed by ultrasonography before and after pentoxifylline-tocopherol treatment, under usual estrogen-progesterone (OP) administration. Result(s): This treatment was well tolerated. All six patients improved significantly in endometrial thickness (6.2 ± 0.6 vs. 3.2 ± 1.1 mm), myometrial dimensions (44 [± 5] × 30 [± 3] × 20 [± 2] vs. 30 [± 7] × 22 [± 3] × 16 [± 2] mm), and diastolic uterine artery flow. Conclusion(s): In young women who want to bear children, the combination of pentoxifylline and vitamin E can reduce fibroatrophic uterine lesions after childhood irradiation.

Intervillous and Spiral Artery Flows in Normal Pregnancies between 5 and 10 Weeks of Amenorrhea Using Color Doppler Ultrasonography

Objective: The aim of our study was to investigate early placental circulation development and spiral and uterine artery flows in normal 1st-trimester pregnancies. Methods: A prospective study of intervillous and spiral artery flows in 49 normal pregnancies (5–10 weeks of amenorrhea) was performed. Transvaginal color and pulsed-wave Doppler techniques (6-MHz probe) were used as routine ultrasound scanning modalities before pregnancy termination for psychosocial reasons. Results: In all pregnancies, between 5 and 10 weeks, continuous nonpulsatile intervillous flow (mean V_max 3.55 cm/s) and spiral artery flow (mean peak systolic velocity 16.2 cm/s, mean diastolic index D/S 0.49 ± 0.089) were detected. In the 47 women in whom the uterine artery flow was measured, the mean peak systolic velocity was 67.5 cm/s, the mean diastolic index was 0.12, and bilateral notching was observed. Conclusions: In all cases, between 5 and 10 weeks, slow and continuous nonpulsatile intrachorionic flow could be detected, whereas pulsatile flow was detected in spiral arteries. The true nature of this early intervillous circulation remains to be determined.

Mechanisms modulating estrogen-induced uterine vasodilation

Estrogen, a potent vasodilator, has its greatest effects in reproductive tissues, e.g., increasing uterine blood flow (UBF) 5- to 10-fold within 90 min after a bolus dose. High-conductance potassium channels and nitric oxide (NO) contribute to the uterine responses, but other factors may be involved. We examined the role of ATP-dependent (ATP-sensitive) and voltage-gated (K v) potassium channels and new protein synthesis in ovariectomized ewes with uterine artery flow probes, infusing intraarterial inhibitors glibenclamide (GLB; K ATP), 4-aminopyridine (4-AP; K v) or cycloheximide, respectively, into one uterine horn before and/or after systemic estradiol-17β (E 2β, 1 μg/kg iv). E 2β alone increased UBF >5-fold and heart rate by 10–25% ( P<.01) within 90 min; mean arterial pressure (MAP) was unaffected. GLB did not alter basal hemodynamic parameters or responses to E 2β. Basal UBF and heart rate were unaffected by 4-AP, but MAP increased by 10% and 25% at 30 and 120 min of infusion ( P<.01), respectively. Although E 2β-induced rises in UBF were unaffected in the control uterine horn, 4-AP dose-dependently inhibited UBF responses in the infused horn ( R=.83, P=.003, n=10). Cycloheximide not only dose-dependently inhibited UBF responses ( R=.57, P=.01, n=18) and increases in uterine cGMP secretion, 23.4±10.7 versus 340±60 pmol/min ( P<.001), but also decreased UBF by 50% and cGMP by ∼90% at the time of maximum UBF. Mechanisms modulating estrogen-induced uterine vasodilation involve signaling pathways that include NO, smooth muscle cGMP, smooth muscle potassium channels and new protein synthesis.

Uterine Artery Embolization for Leiomyomata

Spies, James B.; Ashcher, Susan A.; Roth, Antoinette R.; Kim, Joon; Levy, Elliot B.; Gomez-Jorge, Jackeline

Effect of Ro 61-1790, a selective endothelin-A receptor antagonist, on systemic and uterine hemodynamics and fetal oxygenation in sheep

Objective: Endothelin-1 is reportedly elevated in preeclampsia, and studies in our laboratory have shown that infusion of endothelin-1 produces increased mean arterial pressure, hemoconcentration, and proteinuria, while decreasing uterine blood flow. If a role in preeclampsia is confirmed for endothelin-1, therapeutic intervention may involve selective endothelin-A receptor blockers. Thus, this study was designed to determine the effects of Ro 61-1790, a selective endothelin-A receptor inhibitor, on mean arterial pressure, heart rate, and uteroplacental blood flow in pregnant and nonpregnant sheep. Study Design: Seven pregnant and seven nonpregnant sheep were instrumented with indwelling femoral artery and vein catheters and bilateral uterine artery flow probes, allowing determination of mean arterial pressure, heart rate, and uteroplacental blood flow. After baseline administration, animals received intravenous Ro 61-1790 either 1 mg/kg or 3 mg/kg, and hemodynamic responses were monitored for 120 minutes. Results: Intravenous administration of Ro 61-1790 at 1 mg/kg had no effect on the parameters measured in either group studied. However, at 3 mg/kg, Ro 61-1790 caused an increase in total uterine blood flow in nonpregnant sheep from 22 ± 6 mL/min to 51 ± 15 mL/min. This occurred in the absence of significant changes in mean arterial pressure. In pregnant animals, administration of 3 mg/kg Ro 61-1790 decreased mean (± SEM) uteroplacental blood flow by 20% (from 771 ± 130 mL/min to 621 ± 110 mL/min) and increased uterine vascular resistance transiently. Administration of Ro 61-1790 had no significant effect on fetal mean arterial pressure, heart rate, or oxygenation. Conclusions: These data suggest that endogenous endothelin-1 may play an important role in regulating uterine vascular tone in pregnant and nonpregnant sheep and that inhibition of endogenous endothelin-1 may lead to reductions in uteroplacental perfusion in pregnant animals. (Am J Obstet Gynecol 2002;186:55-60.)

Influence of maternal cigarette smoking on maternal weight gain, uterine and umbilical flow velocities and fetal growth

Objective: To investigate the effects of cigarette smoking during pregnancy on maternal body mass index, maternal weight gain, uterine and umbilical artery flow velocities and fetal growth.Methods: We studied 37 pregnant women (17 cigarette smokers [&gt;10/day] and 20 non‐smokers) using an ATL HDI 5000 scanner for fetal anatomic survey and measurement of uterine and umbilical artery flow velocities. Maternal BMI change and weight gain during pregnancy, uterine and umbilical cord flow velocities, and fetal weight at delivery were measured in all patients.Results: There were no differences between the smoking and non‐smoking groups in gestational age at scanning (23.7 ± 1.5 vs. 26.5 ± 1.3 week), gravid (2.3 ± 0.3 vs. 2.1 ± 0.3) and parity (0.9 ± 0.2 vs. 0.6 ± 0.2). The median maternal BMI was less in smokers than non‐smokers both pre‐pregnancy (19 vs. 24) and at delivery (27.5 ± 1.3 vs. 32.3 ± 1.3). Maternal weight gain was less in smokers than non‐smokers (10.2 ± 1.6 vs. 14.7 ± 1.5 kg, P &lt; 0.05). In the uterine artery, there was no significant difference in the systolic/diastolic ratio between smokers and non‐smokers (1.9 ± 0.1 vs. 1.8 ± 0.1). The umbilical artery systolic/diastolic ratio was greater in smokers than non‐smokers (3.25 ± 0.2 vs. 2.31 ± 0.07, P &lt; 0.05) and fetal weight at delivery was lower in smokers (2.7 ± 0.2 vs. 3.3 ± 0.2 kg, P &lt; 0.05).Conclusions: Decreased BMI and lower weight gain of women who smoke suggest that their nutritional intake may be lower than in non‐smokers. Decreased maternal weight gain in smokers and increased umbilico–placental resistance may both contribute to fetal growth restriction. Smoking appears not to affect utero‐placental resistance.

Ultrasound time domain and color M‐mode analysis of uterine blood flow in twin pregnancy: prediction of uteroplacental complications, placental insufficiency and intrauterine growth restriction

Objectives: A preliminary assessment of the usefulness of a non‐Doppler technique of uterine artery blood flow measurement in twin pregnancy, for the prediction of preeclampsia, utero‐placental insufficiency and intrauterine growth restriction. To compare the results obtained with the contemporary Doppler method.Methods: A prospective study of 32 twin pregnancies presenting consecutively for a routine second trimester ultrasound scan. Maternal demographic and physical characteristics were recorded in all cases. Using previously described methods, blood flow studies were then conducted using the two different techniques; pulsed color Doppler was used to measure blood flow velocity waveform resistance indices, while a time domain correlation technique with color M‐mode imaging was used to measure blood volume flow in both uterine arteries. The placental site and morphology, uterine artery waveform characteristics, and presence or absence of diastolic notches were recorded. The ultrasound fetal growth measurements were plotted on reference charts to assess individual fetal growth patterns, and the obstetric outcomes were recorded for all the pregnancies. Statistical analysis was performed to assess the predictive value of each method of blood flow measurement for the relevant obstetric complications.Exclusions: One mother with sickle cell trait (Hb A + S).Results: An abnormal uterine artery waveform (high resistance with persistence of uterine artery notching) was of limited value in the prediction of pre‐eclampsia and IUGR in twin pregnancies. There was close correlation between a significant reduction in uterine artery blood volume flow and early onset intrauterine growth restriction requiring delivery before 34 weeks gestation. Uterine artery blood volume flow may be less influenced by the placental site compared with traditionally used resistance and pulsatility indices.Conclusions: Uterine artery notching appears to be of limited value in the direct prediction of growth complications in twins. The volume flow method correctly identified all the pregnancies complicated by early onset intrauterine growth restriction. Both methods may well prove to be complementary in the antenatal management of twin pregnancy although further studies will be required.

Establishment of a Simple Method for Measurement of Chronic Blood Flow in Uterine Artery of Pregnant Cows

Blood flow to the gravid uterine horn of seven multiparous Holstein cows (mean±SD, BW = 625.5±82.4kg; age = 4.7±1.7 yr; parity = 2.9±1.1 yr) was measured from d 225 of gestation to parturition using transit-time ultrasonic blood flow probes placed around the middle uterine artery. Surgery was conducted on d 215 of gestation. The cows were sedated with xylazine and local anesthesia (procaine or bupivacain hydrochloride) during surgery. The surgical operations were conducted at the flank of standing cows. A transit time ultrasonic flow probe (“S” series, diameter 12 or 14mm, Transonic Systems Inc., Ithaca, NY) was fitted surgically around the uterine artery of each cow. Surgery was completed within 2h of anesthesia, and the animals recovered rapidly following surgery. Uterine blood flow (UBF, L/min) was recorded at 10-s intervals for 1395min; these values were averaged to determine UBF. Cows exhibited normal gestation lengths (279.1±7.4 d), gave birth to normal healthy calves (birth weight = 40.6±6.6kg), and had no retained placentas. The UBF increased significantly (P<0.01) from d 225 (6.67±2.47) to d 249 (8.23±2.89) of gestation, but the latter UBF was similar to that of d 266 (8.38±2.70). The increased UBF after d 225 indicates increased demand of nutrients of fetus with the progress of gestation. The range of mean UBF varied widely among individual cows from 4.1 L/min to 12.2 L/min. Our method is useful for chronic measurement of UBF in cows for nutritional or physiological studies and does not require sophisticated facilities or special surgical technique.