Transrectal Doppler sonography of uterine blood flow during early pregnancy in mares

Transrectal color Doppler sonography was used for the noninvasive investigation of uterine blood flow in five mares. Both the left and right uterine arteries were scanned to obtain blood flow velocity waveforms during two consecutive estrous cycles and two early pregnancies in each mare. Blood flow was expressed as the time-averaged maximum velocity (TAMV) and the resistance index (RI). In all pregnancies the embryonic vesicle could be detected for the first time on Day 11 (day of ovulation: Day 0). No differences in mean TAMV and RI values of both uterine arteries were observed in comparison to the corresponding days of the estrous cycle until Day 11 of pregnancy (P>0.05). From Day 11 onwards, mean TAMV values were higher and mean RI values lower in pregnant mares than in cyclic mares (P<0.05). During the estrous cycle TAMV and RI values did not differ between the right and left uterine arteries (P>0.05). From Days 15 to 29 of pregnancy, TAMV values were consistently higher and RI values lower in the uterine artery ipsilateral to the conceptus and they had a more distinct rise and decline, respectively, compared to the contralateral uterine artery (P<0.05). The variance component estimates for the effect of mare on TAMV and RI values during pregnancy were 60 and 53%, respectively, and for the effect of day of pregnancy, they were 29 and 34%, respectively (P<0.0001). Within mares there were no significant differences between the two pregnancies with regard to blood flow (P>0.05). The results show that uterine blood supply increases in mares during the second week of pregnancy compared to cyclic mares. Furthermore there are individual variations in blood flow between mares.     

Transrectal Doppler sonography for evaluation of uterine blood flow throughout pregnancy in 13 cows

Once weekly from 30 to 270 days of gestation in 13 cows, Doppler ultrasound scanning (triplex Doppler system) was done to assess blood-flow parameters of both median uterine arteries. Resistance, velocity and volume indices were measured. Resistance index values were negatively correlated to all other blood-flow parameters (P<0.05), but there were positive correlations between velocity and volume indices (P<0.05). Resistance indices were lower, and velocity and volume indices were significantly higher in the median uterine artery ipsilateral versus contralateral to the fetus. Resistance indices decreased continuously during the first 36 weeks of pregnancy. Velocity values rose three-fold, whereas the area increased 20-fold and the volume increased 17-fold by the end of gestation (P<0.05). Birth weight of calves was positively correlated with blood-flow volume (r=0.34) but negatively correlated with the resistance index (r=-0.45). There were no significant differences between male versus female calves (at any stage of gestation) in the resistance, time-average maximum velocity, and volume indices (P>0.05). In conclusion, arterial blood flow was monitored with transrectal Doppler sonography in both median uterine arteries weekly throughout pregnancy in cattle; this could be very valuable for monitoring pregnancies at high risk for abnormalities of the placenta, fetus or both, e.g. cloned calves.     

Transrectal Doppler sonography of uterine and umbilical blood flow during pregnancy in mares

Transrectal color Doppler sonography was used to investigate uterine and umbilical blood flow during pregnancy (duration, 46-48 weeks) in four mares. The resistance index (RI) and blood flow volume (VOL) of the uterine arteries ipsilateral and contralateral to the conceptus, and the presence of an early diastolic notch in the Doppler wave, were evaluated every 4 week throughout pregnancy. Fetal blood flow was calculated semiquantitatively every 2 week (from 20 to 40 weeks), using the RI of the umbilical arteries. During the entire period of investigation, there were no significant individual variations in uterine RI and VOL nor differences between the two uterine arteries. Mean RI decreased by more than half during pregnancy from 0.89 +/- 0.01 to 0.39 +/- 0.03, and mean VOL increased almost 400-fold from 69 +/- 37 to 27,467 +/- 8851 ml/min. There were relationships (P<0.0001) between week of pregnancy (x) and RI as well as VOL. These were described by the equations RI=0.938-0.150 ln(x) and VOL (ml/min)=7.621x(2.157). Log transformed total estrogen (TE) were related to RI (r=-0.879; P<0.05) as well as to VOL (r=0.888; P<0.05). The notch in the Doppler wave of the uterine artery disappeared between 18 and 26 weeks. There was a correlation (P<0.0001) between week of gestation (x) and RI values of the umbilical arteries; this was described by the equation RI=1.763-0.071x+0.001x2. Further studies are needed to determine whether transrectal color Doppler sonography could be used to identify mares at risk of abortion.     

Transrectal Doppler sonography of uterine blood flow

Transrectal Doppler ultrasound was used for the noninvasive investigation of uterine blood flow in cows. Both the left and right Aa. uterinae were scanned to obtain blood flow velocity waveforms over 2 consecutive estrous cycles. Blood flow was reflected by the resistance index (RI) and the time-averaged maximum velocity (TAMV). Intra-observer reproducibility of Doppler measurements was evaluated. The intra-class correlation coefficient (Intra-CC) was 0.97 for the RI and 0.95 for TAMV. While RI values did not differ between the left and right A. uterina (P > 0.05), differences in TAMV occurred between both vessels in 2 cows. These differences were not related to the ovary bearing the dominant follicle or to the corpus luteum (P < 0.001). As in all cows, changes of RI and TAMV values between the left and right artery during the estrous cycle were correlated (correlation coefficient r > 0.72; P < 0.0001); the mean values of both sides were used for subsequent analyses. Variance component estimates for the effect of cow on RI and TAMV were 8 and 13% and for the influence of day of estrous cycle they were 70 and 47%, respectively (P <0.0001). Between estrous cycles no significant differences could be measured within cows (P > 0.05). The highest RI and lowest TAMV values occurred on Day 0 (= day of ovulation) and Day 1, while the lowest RI and highest TAMV values were measured between Days -3 and -1 of the estrous cycle, respectively. There was a positive correlation between TAMV and estrogen concentrations and a negative correlation between RI and plasma estrogen levels. Plasma progesterone levels and TAMV were negatively correlated, but no correlation could be measured (P > 0.05) between RI values and plasma progesterone concentrations. While there were no differences in plasma concentrations of estrogens and progesterone between estrous cycles within cows, the levels of these hormones differed between cows. The results show that transrectal Doppler sonography is a useful, noninvasive method for examining uterine blood flows in cows. If there is an influence of uterine perfusion on fertility in cows its role needs further investigation.     

Doppler sonography of the uterine arteries during a superovulatory regime in cattle. Uterine blood flow in superovulated cattle

Transrectal color Doppler sonography was used to investigate the effects of a gonadotropin treatment to induce superovulation on uterine blood flow and its relationship with steroid hormone levels, ovarian response and embryo yield in dairy cows. The estrous cycle of 42 cows was synchronized by using PGF(2alpha) during diestrus and GnRH 48 h later (Day 0). Cows were examined on the day of eCG (2750 IU)-administration (Day 10), 3 days after eCG (Day 13) and 7 days after artificial insemination (Day 22), including the determination of total estrogens (E) and progesterone (P(4)) in peripheral plasma. Eight days after insemination (Day 23) the uterus was flushed and the number of total ova and embryos as well as transferable embryos was determined. The ovarian response was defined by the number of follicles>5.0mm in diameter on Day 13 and the number of corpora lutea on Day 22. Uterine blood flow was reflected by the blood flow volume (BFV) and the pulsatility index (PI) in the uterine arteries. Both variables showed distinct changes throughout the superovulatory cycle: BFV increased by 94% and PI decreased by 30% between Days 10 and 22 (P<0.0001). On Day 13, BFV but not PI correlated with follicle numbers (r=0.35; P<0.05); no correlation was found with E and P(4) (P>0.05). On Day 22, BFV correlated positively and PI correlated negatively with the number of corpora lutea (r=0.45 and r=-0.37; P<0.05) and P(4) (r=0.39 and r=-0.30; P<0.05). The number of transferable embryos was solely related to BFV measured on Day 13 (r=0.32; P<0.05). Our results show for the first time that in cows a superovulatory treatment is associated with a marked increase in BFV and a marked decrease in PI in the uterine arteries, concurrent with the development of multiple follicles and corpora lutea. However, transrectal color Doppler sonography of the uterine arteries does not facilitate the prediction of embryo yields following superovulatory treatment.     

Effect of xylazine,isoxsuprine, and lidocaine on Doppler sonographic uterine and umbilical blood flow measurements in cows during the last month of pregnancy

The maternal portion of the bovine placenta receives blood mainly from the uterine arteries (AUT) and the fetal portion from the umbilical arteries (AUM). Placental perfusion is crucial for fetal development and undergoes adaptive changes during pregnancy according to the fetal requirements. One goal of this study was to investigate changes in Doppler sonographic measurements of blood vessels that supply blood to the placenta in cows during the last 4 weeks of pregnancy. Another goal was to examine how these measurements are affected by three drugs commonly used in cows at the time of parturition. Nine cows underwent Doppler sonographic examination of the AUT ipsilateral and contralateral to the pregnant horn and one AUM three times per week during the last 4 weeks of gestation. This was followed by the randomized administration of one of the three following experimental drugs per day: isoxsuprine (200 mg/cow, iv), xylazine (2 mg/100 kg, iv), and lidocaine for epidural anesthesia (100 mg/cow). Doppler sonographic examination was repeated 30 minutes after medication. Maternal pulse rate increased during the study period (P < 0.001), and the diameter of the contralateral AUT was smaller in the last week before birth than in the two preceding weeks. The resistance index (RI) of the ipsilateral AUT was smaller in the last week than in the first 2 weeks of the study period. Uterine blood flow volume increased after isoxsuprine by 5% and after epidural anesthesia by 6% (both P ≤ 0.05) and decreased after xylazine by 10% (P < 0.001). Isoxsuprine was the only drug that elevated the blood flow volume in the AUM (P ≤ 0.05). Xylazine increased the RI of both AUT (both P < 0.001) and significantly reduced maternal and fetal pulse frequencies, whereas isoxsuprine significantly reduced the RI of both AUT and the AUM and increased maternal and fetal pulse frequencies. The results reported that Doppler sonographic measurements of uterine and AUM change little in the last month of pregnancy in the cow. Isoxsuprine and epidural anesthesia with lidocaine have the potential to improve uterine perfusion.     

Variability of uterine blood flow in lactating cows during the second half of gestation

The main goal of the present study was to measure uterine blood flow volume (BFV) in the second half of gestation in lactating German Holstein cows. Furthermore, it was investigated, if there are individual variations in uterine blood flow and correlations between uterine blood flow and maternal weight and the birth weight of the calf. Forty-four cows were examined via color Doppler sonography in gestation weeks (GW) 21, 25, 29, 33, 37 and 39. The cows were allocated in groups based on the following variables: body weight (light ≤ 575 kg, heavy > 575 kg) and birth weight of the calf (light ≤ 42 kg, heavy > 42 kg). The BFV was measured via transrectal Doppler sonography of both uterine arteries. There was a linear increase in uterine BFV throughout the study period from 3053 ± 1143 ml/min to 16912 ± 5793 ml/min. Variation coefficients for inter-individual variations ranged from 34 to 37%. There was a moderate correlation between uterine BFV and birth weight of the calf in weeks 21 to 37 (0.30 ≤ r < 0.49; P < 0.05) and a good correlation in week 39 (r = 0.60; P < 0.0001). Uterine BFV in week 21 was significantly (P < 0.01) higher in heavy cows (3394 ± 1119 ml/min) than in light cows (2658 ± 1064 ml/min). Compared with light cows, the increase in uterine BFV was 32% higher in heavy cows during the study period. In week 21, there was no difference (P > 0.05) in uterine BFV between cows carrying a heavy calf (3351 ± 1130 ml/min) and those carrying a light calf (2796 ± 1115 ml/min). Thereafter, the increase of BFV was 43% higher in cows with a heavy calf than in those carrying a light calf. Cows with different body weights, but same birth weight of calf showed no differences (P > 0.05) in the increase of BFV, while in cows with the same body weight the rise in BFV was higher (P < 0.05) in those cows producing a heavy calf compared to cows carrying calves with light birth weights. In conclusion, there was a linear increase in uterine BFV in lactating Holstein cows during the second half of pregnancy with marked individual variations. Differences in the rise of BFV were more caused by the fetus than by body weight of cows.     

Uterine blood flow during the first 3 weeks of pregnancy in dairy cows

Transrectal color Doppler sonography was used to compare changes in uterine blood flow between cyclic and early pregnant lactating dairy cows. Examinations were carried out in 53 multiparous lactating cows on days 3, 6, 9, 11, 13, 15, 18 and 21 (day 0=estrus). Fourteen cows were examined during the estrous cycle and thirty-nine cows after insemination with frozen/thawed sperm. Uterine blood flow was reflected by the time-averaged maximum velocity (TAMV) and the pulsatility index (PI) in the uterine artery ipsilateral to the corpus luteum. Twenty-one cows that were not pregnant on day 25 were excluded from the study. There was high inter-individual variability in PI- (CV: 22-62%) and TAMV-values (CV: 22-42%) at all examinations. In cyclic cows, TAMV values increased between days 13 and 18 and PI values decreased between days 15 and 21 (P<0.05). In pregnant cows (n=18), TAMV values increased from days 9 to 11 and then decreased to minimal values by day 18 (P<0.05). The PI values decreased between days 3 and 11 and then increased to maximum levels on day 18 (P<0.05). On day 21, both variables reached (P<0.05) values that did not differ (P>0.05) from those on day 11. The changes in TAMV were correlated with estrogen and progesterone concentrations (r=0.69 and -0.70, respectively; P<0.05) in cycling cows, but not in pregnant cows (P>0.05). The PI values did not correlate with steroid hormone levels (P>0.05). Differences in uterine blood flow between cycling and early pregnant cows were observed only on day 18 (P<0.05). The results show that in pregnant cows changes in uterine blood supply can be detected already in the second week after insemination; these changes do not occur in the second week of the cycle.     

Uterine blood flow of cows during the oestrous cycle and early pregnancy: effect of the conceptus on the uterine blood supply.

Blood flow to each uterine horn of cows during the oestrous cycle and early pregnancy was determined daily by use of electromagnetic blood flow probes placed around both middle uterine arteries. The pattern of blood flow to uteri of pregnant and non-pregnant cows was similar until Day 14 after mating or oestrus. Between Days 14 and 18 of pregnancy blood flow to the uterine horn containing the conceptus increased (P less than 0.01) 2- to 3-fold, whereas blood flow to the non-gravid uterine horn in these cows remained constant. No corresponding increase in blood flow to the uterine horn ipsilateral to the ovary bearing the CL was observed in non-pregnant cows during this 4-day period. By Day 19 of pregnancy, blood flow to the gravid uterine horn had returned to a level similar to that observed on Day 13. Blood flow to both uterine horns of pregnant cows remained constant from Days 19 to 25 and then increased to the gravid horn (P less than 0.01) markedly until Day 30 whereas blood flow to the non-gravid horn remained low. Uterine blood flow during the oestrous cycle of non-pregnant cows was positively correlated (P less than 0.01) with systemic concentrations of oestradiol and the ratio of oestradiol (pg/ml) to progesterone (ng/ml). There was no association between oestradiol concentrations and blood flow to the gravid uterine horn. These data indicate local control of uterine blood flow by the bovine conceptus which may function to create optimal conditions for the continuation of pregnancy.     

Transrectal color Doppler sonography of the A. uterina in cyclic mares

Color Doppler ultrasound was used transrectally in 6 mares to locate both the left and right Aa. uterinae and to obtain flow velocity waveforms at defined times (Days 0, 5, 10, 15 and 20) during 4 estrous cycles. Blood flow reflected by the resistance index (RI) was determined for both arteries on 120 occasions. As there was no significant difference and a high correlation in the RI values between the left and right arteries (paired Student's t-test, correlation coefficient r > 0.94; P < 0.05), the average RI value was used for subsequent analyses. There were correlations between RI values, mares and day of estrous cycle (P < 0.0001). The mean RI was higher (P < 0.05) in the 2 multiparous mares (age, 12 to 13 yr) than in the 4 younger maiden mares (age, 6 to 10 yr). During the estrous cycle mean RI values on Day 0 (day of ovulation) and Day 10 were higher (P < 0.05) than on Days 5, 15 and 20, whereas between estrous cycles within mares no differences (P > 0.05) could be measured. The results suggest that transrectal Color Doppler sonography is a noninvasive method for examining differences in impedance to uterine blood flow between different mares and cycle periods.     

Luteal blood flow increases during the first three weeks of pregnancy in lactating dairy cows

The objectives of this experiment were to characterize luteal blood flow in pregnant and non-pregnant cows and to determine its value for early pregnancy diagnosis. Lactating dairy cows (n = 54), 5.2 ± 0.2 y old (mean ± SEM), average parity 2.4 ± 0.2, and ≥ 6 wk postpartum at the start of the study, were used. The corpus luteum (CL) was examined with transrectal color Doppler ultrasonography (10.0-MHz linear-array transducer) on Days 3, 6, 9, 11, 13, 15, 18, and 21 of the estrus cycle (estrus = Day 0). Artificially inseminated cows (n = 40) were retrospectively classified as pregnant (embryonic heartbeat on Day 25; n = 18), nonpregnant (interestrus interval 15 to 21 d, n = 18), or having an apparent early embryonic loss (interestrus interval >25 d, n = 4). There was a group by time interaction (P < 0.001) for luteal blood flow from Days 3 to 18; it was approximately 1.10 ± 0.08 cm² (mean ± SEM) on Day 3, and increased to approximately 2.00 ± 0.08 cm² on Day 13 (similar among groups). Thereafter, luteal blood flow was numerically (albeit not significantly) greater in pregnant cows, remained constant in those with apparent embryonic loss, and declined (not significantly) between Days 15 and 18 in nonpregnant cows. Luteal blood flow was greater in pregnant than in nonpregnant (P < 0.05) and nonbred cows (P < 0.05, n = 14) on Day 15 (2.50 ± 0.16, 2.01 ± 0.16, and 2.00 ± 0.18 cm², respectively) and on Day 18 (2.40 ± 0.19, 1.45 ± 0.19, and 0.95 ± 0.21 cm²). In cows with apparent early embryonic loss, luteal blood flow was 2.00 ± 0.34 and 2.05 ± 0.39 cm² on Days 15 and 18, which was less (not significantly) than in pregnant cows, but greater (P < 0.05) than in nonbred cows on Day 18. Although mean luteal blood flow was significantly greater in pregnant than nonpregnant (and nonbred) cows on Days 15 and 18, due to substantial variation among cows, it was not an appropriate diagnostic tool for pregnancy status.     

Doppler sonography of the uterine and ovarian arteries during a superovulatory program in horses

The aim of the present study was to investigate the effects of a gonadotropin treatment to induce superovulation on ovarian and uterine blood flow and its relationship with steroid hormone levels and ovarian response in mares, using color Doppler sonography. Each of six mares were examined sonographically in five cycles for 3 d (t1 to t3) during the follicular development phase (FDP) beginning at a follicle size of ≥ 22 mm, and for 4 d (D-4 to D-1; D0 = Ovulation) in the preovulatory phase (POP). After each examination, total estrogens (E_tot) and progesterone (P₄) levels were determined in peripheral plasma. Cycles 1, 3, and 5 (c₁, c3, c5) were unstimulated cycles (USC); in c2 and c4, the mares were stimulated (SC) with eFSH and inseminated when in estrus at 12 and 24 h after hCG administration. Embryo recovery was performed 6.5 d post ovulation. Cycle 5 c5 was an unstimulated cycle with hCG treatment, insemination, and embryo recovery. Ovarian and uterine blood flow was quantified by the blood flow volume (BFV) and the pulsatility index (PI) in ovarian and uterine arteries. The mean number of ovulations and developing CL was 1.3 ± 0.4 in USC and 4.4 ± 3.1 in stimulated cycles (SC) with no difference (P ≥ 0.05) between the ovaries within mares. No difference (P > 0.05) was observed in utBFV and utPI during FDP between USC and SC, but during POP, utPI was lower (P < 0.05) and utBFV higher (P < 0.001) in SC than USC. The ovBFV was higher (P < 0.01) and ovPI lower (P < 0.05) in SC compared to USC. All uterine and ovarian blood flow parameters were related to the number of developing follicles in SC. Parameters utPI (r = −0.67; P < 0.001) and ovPI (r = −0.53; P < 0.001) were negatively correlated with the number of ovulations on t3, and with the number of collected embryos on t3 (utPI: r = −0.81; P < 0.001), D-4 (utPI: r = −0.64; P < 0.0001), and D-1 (ovPI: r = −0.41; P < 0.01). P₄ levels were not positively correlated with utBFV (P > 0.05), but E_tot concentrations (D-4: r = 0.790; D3: r = 0.639; P < 0.001; D-1: r = 0.48; P < 0.001) and ovBFV from D-4 to D-1 (r = 0.64; P < 0.001) in SC were. The results of the present study show that in mares treatment with gonadotropins to induce superovulation is associated with a marked increase in uterine and ovarian perfusion, concurrent with the development of multiple follicles and an increase in E_tot levels. The increased blood flow seems to be related to the effectiveness of ovarian response to stimulation.     

Effects of maternal nutrient restriction followed by realimentation during midgestation on uterine blood flow in beef cows

The objective was to examine the effect of maternal nutrient restriction followed by realimentation during midgestation on uterine blood flow (BF). On Day 30 of pregnancy, lactating, multiparous Simmental beef cows were assigned randomly to treatments: control (CON; 100% National Research Council; n = 6) and nutrient restriction (RES; 60% of CON; n = 4) from Day 30 to 140 (period 1), and thereafter, realimented to CON until Day 198 of gestation (period 2). Uterine BF, pulsatility index (PI), and resistance index (RI) were obtained from both the ipsilateral and contralateral uterine arteries via Doppler ultrasonography. Generalized least square analysis was performed. Ipsilateral uterine BF in both groups increased quadratically (P < 0.01) during period 1 and linearly (P < 0.01) during period 2. There was a treatment (P = 0.05) effect during period 2; where RES cows had greater ipsilateral BF versus CON. Ipsilateral uterine PI and RI decreased linearly (P ≤ 0.01) during period 1 across treatments. Contralateral uterine BF in CON cows tended (P < 0.09) to be greater versus RES in both periods. Contralateral PI in both groups increased linearly (P ≤ 0.01) during period 1. Contralateral uterine RI was increased (P ≤ 0.05) in RES cows versus CON in both periods. There was no interaction or treatment effect (P ≥ 0.24) for total BF during either period. Nutrient restriction does not alter total uterine BF, but it may increase vascular resistance. However, up on realimentation, local conceptus-derived vasoactive factors appear to influence ipsilateral uterine BF.     

Suppression of trophoblast uterine spiral artery remodeling by estrogen during baboon pregnancy: impact on uterine and fetal blood flow dynamics

The present study was conducted to determine the impact of suppressing trophoblast remodeling of the uterine spiral arteries by prematurely elevating estrogen levels in the first trimester of baboon pregnancy on uterine and umbilical blood flow dynamics. Uteroplacental blood flow was assessed by Doppler ultrasonography after acute administration of saline (basal state) and serotonin on days 60, 100, and 160 of gestation (term: 184 days) to baboons in which uterine spiral artery remodeling had been suppressed by the administration of estradiol on days 25-59 of gestation. Maternal blood pressure in the basal state was increased (P < 0.01), and uterine artery diastolic notching and the umbilical artery pulsatility index and systolic-to-diastolic ratio, reflecting downstream flow impedance, were increased (P < 0.01) after serotonin administration on day 160, but not earlier, in baboons treated with estradiol in early gestation. These changes in uteroplacental flow dynamics in serotonin-infused, estradiol-treated animals were accompanied by a decrease (P < 0.05) in uterine and umbilical artery volume flow and fetal bradycardia. The results of this study show that suppression of uterine artery remodeling by advancing the rise in estrogen from the second trimester to the first trimester disrupted uteroplacental blood flow dynamics and fetal homeostasis after vasochallenge late in primate pregnancy.     

Effect of the prostacyclin synthetase inhibitor tranylcypromine on uterine blood flow in pregnancy

Prostacyclin is a potent vasodilator in a number of vascular beds including the uterus. However, the role of prostacyclin in maintaining uterine blood flow during pregnancy is not well established. Recent reports have appeared suggesting that tranylcypromine can selectively inhibit prostacyclin synthesis. Thus, the present study was undertaken using an unanesthetized chronically catheterized pregnant sheep preparation to evaluate the effects of direct intra-arterial infusions of tranylcypromine on the uterine vasculature of late-term pregnant ewes. Infusions of 1, 3 and 10 mg/min of tranylcypromine led to dose-related reduction in uterine blood flow (16, 21 and 47 percent, respectively) and increased blood pressure (7, 10 and 23 percent, respectively). However, these alterations were not associated with reductions in the uterine production rates of the prostacyclin metabolite, 6-keto-PGF_1α, as determined by unextracted plasma RIA. In addition, pre-treatment of animals with the α-adrenergic blocking agent, phenoxybenzamine, almost totally abolished uterine and systemic blood pressure responses to tranylcypromine. These data suggest that tranylcypromine either releases or elevates levels of an alpha adrenergic stimulant which constricts the uterine and systemic vasculature and does not alter prostacyclin levels at the dose tested.     

Doppler ultrasonographic assessment of maternal and fetal blood flow in abnormal canine pregnancy

The aim of this study was to describe the changes of uterine artery, umbilical artery and fetal abdominal aorta, renal and internal carotid arteries blood flow in abnormal canine pregnancy. Twenty-two, Brucella-negative pregnant bitches were retrospectively classified into abnormal (which had either interrupted their pregnancy between days 52 and 60 or had perinatal death >60% of the litter; n=11) and normal (which had delivered healthy puppies at term; n=11). In all the animals, color and pulsed-wave Doppler examinations of uterine artery were conducted every 10 days from Day 20 to 50 from estimated luteinizing hormone peak. Doppler ultrasonography was also conducted in the fetuses to assess umbilical artery, abdominal aorta, renal and internal carotid arteries from Day 40 to 60 of gestation. Throughout the study, resistance index (RI) of uterine, umbilical and fetal renal arteries decreased up to -15% compared to -36% (P<0.01), -11% compared to -23% (P<0.05) and 2% compared to -13% (P<0.05), respectively in the abnormal and normal bitches. Fetal abdominal aorta and internal carotid did not differ between groups (P>0.05). It is concluded that in dogs, uterine artery, umbilical artery and fetal renal artery RI differ between normal and abnormal gestation being useful for the prediction of adverse obstetric outcome.     

Greater uterine artery blood flow during pregnancy in multigenerational (Andean) than shorter-term (European) high-altitude residents

Multigenerational (Andean) compared with shorter-term (European) high-altitude residents exhibit less hypoxia-associated reductions in birth weight. Because differences in arterial O(2) content are not responsible, we asked whether greater pregnancy-associated increases in uterine artery (UA) blood flow and O(2) delivery were involved. Serial studies were conducted in 42 Andean and 26 European residents of La Paz, Bolivia (3600 m) at weeks 20, 30, 36 of pregnancy and 4 mo postpartum using Doppler ultrasound. There were no differences postpartum but Andean vs. European women had greater UA diameter (0.65 +/- 0.01 vs. 0.56 +/- 0.01 cm), cross-sectional area (33.1 +/- 0.97 vs. 24.7 +/- 1.18 mm(2)), and blood flow at week 36 (743 +/- 87 vs. 474 +/- 36 ml/min) (all P < 0.05) and thus 1.6-fold greater uteroplacental O(2) delivery near term (126.82 +/- 18.47 vs. 80.33 +/- 8.69 ml O(2).ml blood(-1).min(-1), P < 0.05). Andeans had greater common iliac (CI) flow and lower external iliac relative to CI flow (0.52 +/- 0.11 vs. 0.95 +/- 0.14, P < 0.05) than Europeans at week 36. After adjusting for gestational age, maternal height, and parity, Andean babies weighed 209 g more than the Europeans. Greater UA cross-sectional area at week 30 related positively to birth weight in Andeans (r = +0.39) but negatively in Europeans (r = -0.37) (both P < 0.01). We concluded that a greater pregnancy-associated increase in UA diameter raised UA blood flow and uteroplacental O(2) delivery in the Andeans and contributed to their ability to maintain normal fetal growth under conditions of high-altitude hypoxia. These data implicate the involvement of genetic factors in protecting multigenerational populations from hypoxia-associated reductions in fetal growth, but future studies are required for confirmation and identification of the specific genes involved.