Spiral Artery Pulsatility Index Research Articles

Radiomics optimizing the evaluation of endometrial receptivity for women with unexplained recurrent pregnancy loss.

The optimization of endometrial receptivity (ER) through individualized therapies has been shown to enhance the likelihood of successful gestation. However, current practice lacks comprehensive methods for evaluating the ER of patients with recurrent pregnancy loss (RPL). Radiomics, an emerging AI-based technique that enables the extraction of mineable information from medical images, holds potential to offer a more objective and quantitative approach to ER assessment. This innovative tool may facilitate a deeper understanding of the endometrial environment and enable clinicians to optimize ER evaluation in RPL patients. This study aimed to identify ultrasound radiomics features associated with ER, with the purpose of predicting successful ongoing pregnancies in RPL patients, and to assess the predictive accuracy of these features against regular ER parameters. This retrospective, controlled study involved 262 patients with unexplained RPL and 273 controls with a history of uncomplicated full-term pregnancies. Radiomics features were extracted from ultrasound endometrial segmentation images to derive a radiomics score (rad-score) for each participant. Associations between rad-scores, baseline clinical variables, and sonographic data were evaluated using univariate and multivariate logistic regression analyses to identify potential indicators of RPL. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive accuracy of the rad-score and other identified indicators in discriminating RPL cases. Furthermore, the relationships between age and these identified indicators were assessed via Pearson correlation analysis. From the 1312 extracted radiomics features, five non-zero coefficient radiomics signatures were identified as significantly associated with RPL, forming the basis of the rad-score. Following multivariate logistic regression analysis, age, spiral artery pulsatility index (SA-PI), vascularisation index (VI), and rad-score emerged as independent correlates of RPL (all P<0.05). ROC curve analyses revealed the superior discriminative capability of the rad-score (AUC=0.882) over age (AUC=0.778), SA-PI (AUC=0.771), and VI (AUC=0.595). There were notable correlations between age and rad-score (r=0.275), VI (r=-0.224), and SA-PI (r=0.211), indicating age-related variations in RPL predictors. This study revealed a significant association between unexplained RPL and elevated endometrial rad-scores during the WOI. Furthermore, it demonstrated the potential of rad-scores as a promising predictive tool for successful ongoing pregnancies in RPL patients.

Effects of Dydrogesterone Tablets Combined with Zishen Yutai Pills on Threatened Abortion in Early Pregnancy and Pregnancy Outcomes.

Objective To explore the effect of dydrogesterone tablets combined with Zishen Yutai pills on threatened abortion in early pregnancy and pregnancy outcomes. Methods This study retrospectively analyzed the clinical data of 100 patients with threatened abortion in early pregnancy who came to the Linhai Second People's Hospital/Taizhou Municipal Hospital from January 13, 2021, to January 13, 2022. According to different treatment methods, 48 patients treated with progesterone injection were assigned to the control group (CG), while 52 cases with the combined therapy of dydrogesterone tablets and Zishen Yutai pills were assigned to the observation group (OG). The two groups were compared in terms of the following parameters: treatment efficacy, whole blood high shear viscosity, hematocrit (HCT), plasma fibrinogen (FIB) level, spiral artery pulsatility index (PI), uterine spiral artery blood flow resistance index (RI), lumbar and abdominal pain relief time, hemostasis time, estrogen levels, pregnancy outcomes, neonatal adverse outcomes, and incidence of adverse reactions. Results Compared with CG, the therapeutic effect in OG was observed to be evidently better, and its pain relief time and hemostasis time in the waist and abdomen were markedly shorter. After treatment, the whole blood high shear viscosity, FIB, RI, PI, and estrogen levels of both groups improved statistically compared with those before treatment, with more significant improvements in OG compared with CG. OG was also superior to CG with markedly lower incidence of preterm birth, miscarriage, neonatal adverse outcomes, and adverse reactions and a drastically higher full-term pregnancy rate. Conclusion Zishen Yutai pill combined with dydrogesterone tablets is of remarkable therapeutic effect in treatment of early threatened abortion, which can significantly improve clinical symptoms and pregnancy outcomes of patients, with a high safety profile, which is worthy of clinical application.

Diagnostic accuracy of uterine artery and spiral artery Doppler for evaluation of endometrial pathology in postmenopausal bleeding

IntroductionTraditional diagnostic workup for Endometrial carcinoma in women with post-menopausal bleeding (PMB) involves endometrial biopsy. Addition of colour and power Doppler ultrasound to transvaginal ultrasonography (TVS) might help in differentiating subset of women who are at high risk of carcinoma. The aim of this study was to determine the diagnostic value of Pulsatility Index (PI) and Resistance Index (RI) of uterine and spiral artery in PMB and to determine the diagnostic value of power Doppler flow mapping in them. Material and methodsA prospective study was done amongst 50 women with PMB. All women were subjected to TVS including uterine artery and spiral artery Doppler velocimetry, power Doppler flow mapping of spiral artery, hysteroscopy and endometrial biopsy. ResultsUterine artery PI and RI values were overlapping between benign and malignant endometrial pathologies. Whereas spiral artery PI ≤ 0.33 and RI ≤ 0.5 helps in differentiating malignant frombenign pathology. Power Doppler multiple vessel pattern is also found to have a better diagnostic ability in picking endometrial cancer. ConclusionAddition of spiral artery velocimetry and power Doppler flow mapping to those with thickened endometrium, aids in differentiating endometrial malignancy from benign pathology. This might be helpful in counselling the women for endometrial biopsy, as histopathological analysis is the gold standard diagnostic modality.

Complementary and Alternative Medicine for the Treatment of Abnormal Endometrial Conditions in Women with PCOS: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Background Endometrial lesions in patients with polycystic ovary syndrome (PCOS) exhibit complex pathological features, and these patients are at risk of both short-term and long-term complications. Complementary and alternative medicine (CAM), which is gradually becoming more accepted and is believed to be clinically effective, claims to be promising for treating PCOS, and thus its effect on the abnormal endometrium of PCOS patients should be assessed. The present meta-analysis sought to evaluate the efficacy and safety of CAM in treating endometrial lesions in patients with PCOS. Methods Randomized trials on CAM were identified in four Chinese and seven English-language databases from their establishment to January 2020. The present study included patients diagnosed with PCOS and abnormal endometrial conditions who underwent CAM therapy independently or in combination with traditional western medicine. Data were extracted, and the Cochrane “risk of bias” tool was used to assess methodological quality. Effects were expressed as the relative risk (RR) or mean difference (MD/SMD) with 95% confidence interval (CI) as calculated with Rev Man 5.3. Results A total of 13 randomized controlled trials were included, involving 1,297 PCOS patients treated for endometrial abnormalities. Methodological quality was generally unclear or had a low risk of bias. The trials tested four different types of CAM therapies (i.e., traditional Chinese medicine treatment, acupuncture treatment, traditional Chinese medicine in combination with western medicine treatment, and acupuncture in combination with western medicine treatment). CAM treatment could significantly reduce the endometrial thickness in PCOS patients compared to western medicine alone (SMD −0.88, 95% CI [−0.12, −0.57]; I2 = 64%). Compared with clomiphene treatment for the induction of ovulation, CAM treatment showed a clear improvement in endometrial thickness during ovulation (SMD 2.03, 95% CI [1.64, 2.02]; I2 = 48%). Moreover, CAM was more effective than western medicine alone in reducing the endometrial spiral artery pulsatility index. No significant difference was seen between CAM and traditional treatment when these were used to improve traditional Chinese medicine syndrome scores. Acupuncture alone or traditional Chinese medicines (taken orally) in combination with western medicine significantly increased the pregnancy rate of PCOS patients (RR 1.59, 95% CI [1.30, 1.93]; I2 = 51%, P < 0.00001), and CAM was more effective than western medicine alone for improving hormone levels. No serious adverse events were reported in 11 of the 13 trials. Conclusions CAM may effectively ameliorate the endometrial condition of PCOS patients, and it can regulate the level of hormone secretion to increase the ovulation rate and the pregnancy rate.

Spiral artery blood flow during pregnancy: a systematic review and meta-analysis

BackgroundDownstream remodeling of the spiral arteries (SpA) decreases utero-placental resistance drastically, allowing sustained and increased blood flow to the placenta under all circumstances. We systematically evaluated available reports to visualize adaptation of spiral arteries throughout pregnancy by ultra-sonographic measurements and evaluated when this process is completed.MethodsA systematic review and meta-analysis of spiral artery flow (pulsatility index (PI), resistance index (RI) and peak systolic velocity (PSV)) was performed. English written articles were obtained from Pubmed, EMBASE and Cochrane Library and included articles were assessed on quality and risk of bias. Weighted means of Doppler indices were calculated using a random-effects model.ResultsIn healthy pregnancies, PI and RI decreased from 0.80 (95% CI: 0.70–0.89) and 0.50 (95% CI: 0.47–0.54) in the first trimester to 0.50 (95% CI: 0.45–0.55, p < 0.001) and 0.39 (95% CI: 0.37–0.42, p < 0.001) in the second trimester and to 0.49 (95% CI: 0.44–0.53, p = 0.752) and 0.36 (95% CI: 0.35–0.38, p = 0.037) in the third trimester, respectively. In parallel, PSV altered from 0.22 m/s (95% CI: 0.13–0.30 m/s) to 0.28 m/s (95% CI: 0.17–0.40 m/s, p = 0.377) and to 0.25 m/s (95% CI: 0.20–0.30 m/s, p = 0.560) in the three trimesters. In absence of second and third trimester Doppler data in complicated gestation, only a difference in PI was observed between complicated and healthy pregnancies during the first trimester (1.49 vs 0.80, p < 0.001). Although individual studies have identified differences in PI between SpA located in the central part of the placental bed versus those located at its periphery, this meta-analysis could not confirm this (p = 0.349).ConclusionsThis review and meta-analysis concludes that an observed decrease of SpA PI and RI from the first towards the second trimester parallels the physiological trophoblast invasion converting SpA during early gestation, a process completed in the midst of the second trimester. Higher PI was found in SpA of complicated pregnancies compared to healthy pregnancies, possibly reflecting suboptimal utero-placental circulation. Longitudinal studies examining comprehensively the predictive value of spiral artery Doppler for complicated pregnancies are yet to be carried out.

Role of transvaginal Doppler sonography in cases of irregular uterine bleeding with depot medroxyprogesterone acetate

Objectives To evaluate role of transvaginal Doppler sonography in cases of irregular uterine bleeding with depot medroxyprogesterone acetate (DMPA). Background Abnormal uterine bleeding is the leading cause of cessation of DMPA use. The definite mechanism of abnormal uterine bleeding has remained vague. Transvaginal Doppler is a noninvasive technique for studying Doppler changes of uterine and spiral artery in cases of abnormal uterine bleeding with DMPA. Patients and methods A case–control study was done on two groups of users of DMPA, one group included 21 cases with abnormal uterine bleeding, and the second group included 21 cases with amenorrhea. Transvaginal sonography was done, and endometrial thickness was measured in greatest sagittal section of the uterus. Uterine and spiral artery pulsatility index (PI) and resistance index (RI) were measured. Data were collected and tabulated. Results Significant changes in PI and RI of uterine and spiral arteries were detected. Uterine artery RI and PI were lower in bleeding group (P = 0.003 and 0.021, respectively), and spiral artery RI and PI were lower in bleeding group (P = 0.0007 and 0.0003, respectively). Conclusion Abnormal uterine bleeding with DMPA is associated with hemodynamic changes in transvaginal Doppler in form of increased blood flow in uterine and spiral arteries as indicated by significant decrease in RI and PI of both arteries.

Three-Dimensional Angiogenic Evaluation of the Effect of Mifepristone in Early Gestation: Pilot Study

Mifepristone (RU486) it is known as an effective abortifacient and postcoital contraceptive method, whose mechanism is not yet known. We carried on a pilot study with the aim of determining the effect that Mifepristone could have in utero-placental vascular compartment during the first trimester of pregnancy compared with placebo. This is a randomized, double-blind, placebo-controlled research. We randomly assigned to two groups patients requesting pregnancy termination with a gestational age between 9th and 11st weeks: Group A receiving placebo and Group B receiving RU. With transvaginal ultrasound tridimensional probe we measured at an initial time (t1) and then 4 hours after administration of Mifepristone or placebo (t2) Doppler parameters: uterine arteries mean Resistance Index, spiral arteries Resistance Index, intervillous flow, umbilical Resistance Index and tridimensional vascular settings and the placental volume. We observed how Mifepristone shows an immediate selective hemodynamic effect in trophoblastic tissue in the first hours of administration. A significant decrease in spiral arteries pulsatility index was demonstrated, without modifying uterine maternal and fetal territories or the other studied parameters. Angiopower 3D evaluation of the interface maternal fetal is complex and encourages to carry further investigations carry further investigations.

A comparative analysis of arterial blood flow in unexplained infertility, tubal infertility and fertile groups

We aimed to compare ovarian (O), uterine (U) and spiral (S) artery (A) resistance of patients diagnosed as fertile, unexplained infertility (UI) and tubal factor infertility (TFI) in the peri-implantation period and independent from the impact of the treatment. UI (n = 70), TFI (n = 75) and fertile (n = 72) patients’ ovarian, uterine and spiral artery pulsatility index (PI), resistance index (RI) and the endometrial thickness, serum estradiol and progesterone levels were compared. The specificity and sensitivity values were calculated according to determined cutoff values. Both TFI and control groups’ UA PI values were significantly lower than the UI group’s PI values. The highest UA RI values were found in UI group and the lowest values were in the control group. UI and TFI groups’ OA PI/RI values were significantly higher than the control group. Both the control and TFI groups’ SA PI/RI values were significantly lower than UI group’s PI/RI values. UI patients’ uterine and spiral arteries PI values >1.86 and >0.85, RI values >0.80 and >0.53 can be used as a valuable test showing reduced uterine perfusion. Ovarian artery PI values >0.96 and RI values >0.58 can be used as tests showing decreased ovarian perfusion in patients with TFI. In these patients, embryo cryopreservation can be considered.

70: Low-dose aspirin reduces uteroplacental vascular impedance during the first half of pregnancy in IVF/ICSI patients: A randomized placebo-controlled study

We hypothesized that low-dose aspirin improves uteroplacental hemodynamics in unselected IVF/ICSI subjects when medication is started concomitantly with controlled ovarian hyperstimulation. Thirty-five pregnant women who had undergone IVF/ICSI and had been randomized to receive 100 mg aspirin (n = 15) or placebo (n = 20) daily starting on the first day of controlled ovarian hyperstimulation were included in this study. There were 4 twin pregnancies in aspirin group and 3 in placebo group. Altogether, 19 fetuses were exposed to aspirin and 23 fetuses to placebo. Doppler ultrasonography was performed at 6+, 10+, 13+ and 18+ gestational weeks. Uterine (UtA) and spiral artery pulsatility index (PI) values were calculated and bilateral UtA notch was noted. Subplacental arcuate artery PI values were obtained at 6+ and 10+ weeks. Umbilical artery PI values and mean velocity were calculated at 10+, 13+ and 18+ weeks. At 6+ weeks, arcuate artery PIs were lower (p = 0.02) in aspirin group (1.71±0.43) compared to placebo group (2.34±0.61). At 18+ weeks, right (p = 0.026) and left (p = 0.044) UtA PIs were lower in aspirin group (0.79±0.37 and 0.87±0.35) than in placebo group (1.14±0.43 and 1.20±0.49). At 18+ weeks, bilateral UtA notch tended (p = 0.06) to be more common in placebo group (40%) than in aspirin group (13%). Umbilical artery PIs and mean velocity did not differ significantly between the groups. Low-dose aspirin reduced uteroplacental vascular impedance in early and mid pregnancy in unselected IVF/ICSI patients when medication was started concomitantly with controlled ovarian hyperstimulation. This may reflect improved throphoblastic invasion and remodeling of spiral arteries. Aspirin did not affect umbilicoplacental circulation during the first half of pregnancy.

Doppler examination of uteroplacental circulation in early pregnancy: Can it predict adverse outcome?

To determine whether spectral Doppler measurements obtained from bilateral uterine, arcuate, radial, and spiral arteries in early gestation correlate with adverse pregnancy outcome. One hundred five pregnant women underwent transvaginal Doppler sonographic examination of uteroplacental circulation at 6-12 weeks' gestation. Resistance index (RI) and pulsatility index (PI) of bilateral uterine, arcuate, radial, and spiral arteries were measured. Diameters of gestational sac (GS) and yolk sac, crown-rump length (CRL), GS-CRL difference, and GS/CRL ratio were also recorded. Correlation was made with pregnancy outcome. Sixteen women developed adverse pregnancy outcome. In these women, right uterine artery PI and RI were significantly higher than in women with normal obstetrical outcome. Spiral artery PI and RI values were also higher, but the difference was not statistically significant. GS-CRL difference, GS/CRL ratio, and yolk sac diameters were significantly lower in this group. Transvaginal Doppler examination can detect hemodynamic changes in uteroplacental circulation associated with subsequent adverse pregnancy outcome.

Uteroplacental Hemodynamics during Early Human Pregnancy: A Longitudinal Study

Background: To determine normal physiologic changes in the uteroplacental hemodynamics during early placental development in the first trimester of pregnancy. Methods: Sixteen normal singleton pregnancies were included in this longitudinal study. Transvaginal Doppler ultrasonographic examinations of uterine, arcuate, radial and spiral arteries were performed at the 5th, 7th, 8th and 10th completed gestational weeks. Peak systolic velocity (PSV), time-averaged maximum velocity (TAMXV) and the pulsatility index (PI) were measured. Results: Uterine artery PSV, TAMXV and PI remained unchanged from the 5th to the 8th week of gestation. From the 8th to the 10th week, PSV (p = 0.02) and TAMXV (p = 0.005) increased and PI decreased (p = 0.006). Changes in the arcuate arteries were similar to those in uterine arteries. No significant changes in PSV, TAMXV or PI of the radial artery were noticed. Spiral artery PSV (p = 0.02) and TAMXV (p = 0.02) increased from the 5th to the 7th week. Thereafter they remained unchanged. Spiral artery PI decreased from the 5th to the 10th week, (p = 0.004). Throughout the study period, the PSV, TAMXV and PI values were significantly higher in the uterine artery than in the arcuate artery, and in the arcuate artery compared with the radial artery. At the 5th gestational week, no differences in PSV and TAMXV were found between radial and spiral arteries. From the 7th gestational week onwards, PSV and TAMXV were significantly lower in the radial artery than in the spiral artery. However, the PI values in the radial artery were significantly higher compared with those in the spiral artery during the whole study period. Conclusions: Spiral artery impedance decreases and blood flow velocities increase as early as between the 5th and the 7th weeks of gestation. During that period, the uterine and arcuate artery hemodynamics remain unchanged. In the uterine and arcuate arteries, decreases in impedance and increases in absolute velocities are detected after the 8th week of gestation. This delay between the changes in the spiral and uterine arteries may represent the magnitude of the increase of placental volume and spiral arterial involvement which is needed to affect uterine hemodynamics.

Prospective longitudinal study of ultrasound screening for endometrial abnormalities in women with breast cancer receiving tamoxifen

Objective The goal of this work was to study the role of transvaginal ultrasonography (TVUS) together with colorflow Doppler imaging (CFDI) in the detection of significant endometrial abnormalities induced by tamoxifen. Methods Over a 6-year period, 304 women on tamoxifen as adjuvant therapy for breast cancer were recruited into the current study. Standard demographic data as well as duration of tamoxifen use were collected. Patients were assessed at study entry and at yearly intervals with TVUS together with CFDI. All patients had an endometrial biopsy at the time of study entry, and repeat endometrial evaluations were done subsequently only if there were abnormal ultrasound findings or the presence of irregular vaginal bleeding. All ultrasonic characteristics and Doppler flow measurements were recorded. Descriptive statistics were used to describe the study group. Logistic regression was used to identify significant treatment- and ultrasound-related factors associated with the presence of significant uterine pathology. Results One thousand and sixty-one ultrasound assessments were performed on 304 patients over a 6-year period. The mean age was 52.33 (range, 29–79). Seventy-two percent of the patients were postmenopausal at the time of breast cancer diagnosis. The median concentrations of estrogen and progesterone receptor were 75 and 73 fmol/L, respectively. Fifty-eight percent of the patients had received cytotoxic chemotherapy. The mean duration of tamoxifen use was 48.2 months. Thirty-two percent of the ultrasound examinations had associated significant uterine pathology defined as conditions that required further medical or surgical investigation and treatment. However, 80% of the abnormalities represented benign polyps. Six cases of primary endometrial cancer were detected. All cases presented with irregular bleeding. No recurrence of disease was detected at a median follow-up of 48 months. One case of metastatic breast cancer to the uterus was encountered. By setting the endometrial thickness cutoff at more than 9 mm to represent significant abnormality in this patient population, the sensitivity was 63.3%, specificity was 60.4%, positive predictive value was 43.3%, and negative predictive value was 77.5%. To detect endometrial cancer, the endometrial thickness cutoff at 9 mm had a positive predictive value of only 1.4%. Logistic regression analysis showed only endometrial thickness greater than 9 mm (OR 3.99, CI = 1.26–12.65, P = 0.018) and spiral artery pulsatility index measurement (OR 4.18, CI = 1.25–13.92, P = 0.02) to be associated with significant uterine abnormalities. Conclusions Routine sequential ultrasound surveillance in asymptomatic women on tamoxifen is not useful because of its low specificity and positive predictive value. A significant portion of screened asymptomatic women would need to undergo needless surgical evaluations of their endometrium if widespread use of ultrasound is implemented in this patient population.

Endometrial receptivity in an in vitro fertilization program as assessed by spiral artery blood flow, endometrial thickness, endometrial volume, and uterine artery blood flow

Objective: To investigate the role of sonographic parameters in assessing endometrial receptivity in an in vitro fertilization (IVF) program. Design: Prospective clinical study. Setting: University setting. Patient(s): One hundred thirty-five patients in our IVF program, selected prospectively on the day of oocyte retrieval. Intervention(s): Transvaginal ultrasound examination was performed before oocyte collection. Main Outcome Measure(s): Association between implantation rate and spiral artery blood flow (primary outcome measure) and between implantation rate and endometrial measurements as well as uterine artery blood flow (secondary outcome measures). Result(s): Overall implantation rate was 23.7% per cycle. Subendometrial blood flow was detected in 113 (83.7%) cases, with pregnancy occurring in 21.2%. Mean spiral artery pulsatility index values were 1.12 ± 0.28 and 1.21 ± 0.27 for nonconception and conception cycles, respectively. Nondetectable spiral artery blood flow was not associated with a lower implantation rate. Neither endometrial thickness nor endometrial volume was correlated with the likelihood of successful implantation. Minimum endometrial thickness and volume associated with pregnancy were 6.9 mm and 1.59 mL, respectively. Conclusion(s): Neither Doppler sonography of the spiral or uterine arteries nor measurement of the endometrial thickness or volume allowed a reliable prediction of subsequent IVF outcome.

Relationship of uterine blood flow to chorionic sac and embryo growth rates

The embryonic period of development is characterized by marked variability in the rate of embryonic growth and development. Differences in uterine blood flow may explain this variability. We investigated the relationship between uterine artery blood flow volume (VOL), uterine artery pulsatility index (UA-PI), uterine artery resistance index (UA-RI), spiral artery pulsatility index (SA-PI), spiral artery resistance index (SA-RI), chorionic sac diameter (CSD), and crown-rump length (CRL) during 321 first trimester vaginal colour Doppler ultrasound examinations of 94 delivered or continuing pregnancies. After correcting for the confounding effect of gestational age, subject, and serum hormone levels by Analysis of Covariance, CRL was related to UA-PI (P = 0.025) and UA-RI (P < 0.001), but not to VOL, SA-PI, or SA-RI. No relationship was found between CSD and any uterine blood flow variables. Serum oestradiol levels were related to CSD and CRL (P < 0.001). No relationship was found to progesterone, maternal age, parity, or previous abortion. We conclude that differences in uterine blood flow and serum oestradiol explain some of the variability in the rate of embryo growth during the first 12 gestational weeks.

Effect of standing on non-pregnant uterine blood flow.

Uterine artery blood flow measurements made solely in the recumbent position may miss physiological changes that occur while patients are upright. We evaluated the effect of standing on the minute blood flow volume of the ascending uterine artery, the pulsatility index (PI), resistance index (RI) and waveforms and on the PI and RI of the myometrial spiral arteries and waveforms at 3-8 and at 9-14 min standing in 74 non-pregnant women. At 9-14 min, the uterine artery blood flow volume had decreased by an average of 34% and the RI had significantly increased in 70% of subjects. Decreased uterine artery blood flow volume was associated with increased distal resistance and with decreased vessel diameter, possibly due to stretching or kinking of the uterine arteries. Changes in the spiral artery PI paralleled changes in the uterine artery PI at 9-14 min, but were less pronounced. Spiral artery PI and RI were not related to the uterine artery blood flow volume while women were recumbent, although they were significantly related while women were standing. The effects of age, uterine mobility and uterine position on uterine artery or spiral artery blood flow were apparent only while women were standing. We conclude that standing as well as recumbent studies are necessary when uterine and myometrial blood flow are evaluated, and that uterine flow volume per minute should be measured whenever possible.