Reference Values for Blood Flow Velocity in the Uterine Artery in Normal Pregnancies from 18 Weeks to 42 Weeks of Gestation Calculated by Automatic Doppler Waveform Analysis

Abstract

The goal of the present study was to establish new Doppler reference ranges for maternal heart rate, intensity-weighted mean blood flow velocities (Vmean) and impedance indices (PI, RI) for the uterine artery by automated waveform analysis. Materials and Methods: A cross-sectional prospective study of 921 low-risk pregnancies was performed at 18 -42 weeks of gestation. Uterine blood flow velocities were derived with pulsedwave color Doppler. Measurements were carried out 1 to 2 cm above the crossing of the uterine and external iliac arteries. Reference ranges for the individual measuring parameters were constructed based on a growth function from a fourparameter class of monotonic continuous functions according to the smallest square principle. Results: A significant increase in intensityweighted mean uterine blood flow velocities was observed at 18 -42 weeks of gestation (Vmean = 43 cm/s to 50 cm/s (p < 0.001)). Reference curves for the pulsatility and resistance indices (PI, RI) significantly decreased with progressing gestation (PI: 18 weeks: 0.89; 42 weeks: 0.65 and RI: 18 weeks: 0.45; 42 weeks: 0.35). No significant PI and RI differences were observed when different placental locations were compared. The maternal heart rate decreased from 88 bpm to 77 bpm. Conclusion: Normal ranges for blood flow velocities and impedance indices in the uterine artery were established by Doppler ultrasound antenatal examinations of a large population of low-risk pregnancies. The data are proposed as reference curves to allow the early diagnosis of maternal and fetal risks.

Fetal Hemodynamic Parameters in Low Risk Pregnancies: Doppler Velocimetry of Uterine, Umbilical, and Middle Cerebral Artery

“…Our study showed a trend to decreasing values for 5 and 50 percentiles, but no regular pattern for the 95th. These decreasing values are in agreement with other studies [10, 30, 31]. A point to be considered is the influence of the patient selection criteria on the PI absolute values among all the studies, considering that some of them included smokers, excluded women with a diastolic notch, or selected women only with certain placenta location.…”

“…A point to be considered is the influence of the patient selection criteria on the PI absolute values among all the studies, considering that some of them included smokers, excluded women with a diastolic notch, or selected women only with certain placenta location. For the SV, the values increased through pregnancy and our values were considerably higher than those reported by Bahlmann et al [31]. …”

Maternal Cardiac Output and Fetal Doppler Predict Adverse Neonatal Outcomes in Pregnant Women With Heart Disease

“…Fetal ultrasound imaging was performed by certified obstetrical sonographers on 2 occasions during the antepartum period (early, ≤26 weeks gestation and late, ≥27 weeks gestation) using an iU22 ultrasound system (Philips Medical Systems). On all ultrasound studies, pulsed Doppler profiles of the free loop of the umbilical arteries and the proximal uterine arteries were obtained and pulsatility index was calculated [PI]; for the uterine artery waveforms, the presence or absence of early diastolic notching was also recorded . Umbilical artery recordings were performed in the absence of fetal breathing or fetal movements according to accepted standards of practice .…”

“…A decline in cardiac output was designated as a decrease in cardiac output that exceeded the observer variability as delineated by percentage error between the 2 measurements of cardiac output. Umbilical or uterine Doppler parameters were classified as abnormal, signifying increased vascular resistance, if the PI exceeded the 95% confidence limits for gestational age or if bilateral systolic notching of the Doppler spectrum was evident …”

High-flavanol and high-theobromine versus low-flavanol and low-theobromine chocolate to improve uterine artery pulsatility index: a double blind randomized clinical trial

“…First, we selected women with bilateral UtA notches and elevated UtA PI, two surrogate markers of deep placentation with questionable predictive values for PE when performed in the first-trimester. Second, we used UtA PI references' chart that has been established using transvaginal ultrasound: UtA PI assessed through transvaginal ultrasound is typically associated with higher values than transabdominal ultrasound in the 1 st trimester with the difference between the two approaches becoming smaller with gestational age [20,21] . Magnesium may have some anti-inflammatory properties because it reduces leukocyte activation [22] .…”