Citation, DOI, disclosures and article data
Citation:
Weerakkody Y, Sharma R, Knipe H, et al. Umbilical arterial systolic / diastolic ratio. Reference article, Radiopaedia.org (Accessed on 29 Mar 2024) https://doi.org/10.53347/rID-71456
Umbilical arterial systolic/diastolic (S/D) ratio is a parameter used in obstetric imaging as part of umbilical arterial (UA) Doppler assessment. It is the ratio between the systolic velocity and the diastolic velocity.
Practical points
The reference range varies through the stage of pregnancy. If there is an increase in the resistance to blood flow through the umbilical artery, this is seen as an increase in the systolic/diastolic (S/D) flow ratio.
The S/D ratio mean value decreases with fetal age 1:
at 20 weeks, the 50th percentile for the S/D ratio is 4
at 30 weeks, the 50th percentile is 2.83
at 40 weeks, the 50th percentile is 2.18
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1. Acharya G, Wilsgaard T, Berntsen G, Maltau J, Kiserud T. Reference Ranges for Serial Measurements of Umbilical Artery Doppler Indices in the Second Half of Pregnancy. Am J Obstet Gynecol. 2005;192(3):937-44. doi:10.1016/j.ajog.2004.09.019 - Pubmed
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2. Weiner C. The Relationship Between the Umbilical Artery Systolic/Diastolic Ratio and Umbilical Blood Gas Measurements in Specimens Obtained by Cordocentesis. Am J Obstet Gynecol. 1990;162(5):1198-202. doi:10.1016/0002-9378(90)90016-z - Pubmed
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