Longitudinal assessment of spiral artery and intravillous arteriole blood flow and adverse pregnancy outcomes.

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Ultrasound in Obstetrics & Gynecology


OBJECTIVE: Superb microvascular imaging (SMI) has been shown in many systems to improve visualization of small vessels by suppressing global motions while preserving low-flow components such as the micro-vessels in the placenta. We sought to determine if SMI-aided visualization of flow velocities in spiral artery (SA) and fetal arterioles in intravillous (IV) space could predict fetal growth restriction (FGR), gestational hypertension (GHT) and/or preeclampsia (PE).

MATERIAL AND METHODS: This was a prospective longitudinal study over a 5-year period. We measured SA and IV flow velocity using SMI-aided Color Doppler between 11 to 13 + 6, 18 to 22 + 6/7 and 28 to 34+ 6/7 weeks of gestation. SA and IV flow velocities were reported as resistance indices (RI). RI values were analyzed with multilevel modeling: individual regression curves were estimated and combined to obtain the reference intervals for SA and IV flow velocities in normal pregnancies. FGR was defined as estimated fetal weight < 10th percentile. Student t-tests compared deviation from expected flow velocity between normal and complicated pregnancies.

RESULTS: Among 540 pregnancies included; 18 (3.3%) had FGR, 31 (5.7%) PE and 61 (11.3%) GHT. In uncomplicated pregnancies, the RI of SA decreased progressively with advancing gestational age. Alternatively, IV RI increased with gestational age. Mean RI values for SA was significantly higher in the FGR and PE groups compared with uncomplicated pregnancies in the third trimester. There was no significant difference in mean RI between uncomplicated pregnancies and those with GHT at any gestational age. When all adverse outcomes were combined, increased SA RI was significantly associated with these outcomes only in the third trimester when compared with the control group [mean RI (SD)= 0.29(0.12) versus 0.27(0.11), respectively; p=0.04]. When SA RI is used to screen for FGR, the area under the receiver operating curves are: 0.68, 0.73 and 0.73, in the first, second and third trimesters, respectively.

CONCLUSION: Significant differences were seen only in those pregnancies at risk for FGR and PE late in pregnancy. Larger studies are needed to determine if SA and IV arteriole flow are reliable predictors of adverse pregnancy outcomes. This article is protected by copyright. All rights reserved.





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