Abstract
Introduction Doppler sonography of the uterine artery (UA) is done to monitor pregnancies, because
the detected flow patterns are useful to draw inferences about possible disorders
of trophoblast invasion. Increased resistance in the UA is associated with an increased
risk of preeclampsia and/or intrauterine growth restriction (IUGR) and perinatal mortality.
In the absence of standardized figures, the normal ranges of the various available
reference curves sometimes differ quite substantially from one another. The causes
for this are differences in the flow patterns of the UA depending on the position
of the pulsed Doppler gates as well as branching of the UA. Because of the discrepancies
between the different reference curves and the practical problems this poses for guideline
recommendations, we thought it would be useful to create our own reference curves
for Doppler measurements of the UA obtained from a singleton cohort under standardized
conditions.
Material and Methods This retrospective cohort study was carried out in the Department of Obstetrics of
the Charité – Universitätsmedizin Berlin, the Department for Obstetrics and Prenatal
Medicine of the University Hospital Halle (Saale) and the Center for Prenatal Diagnostics
and Human Genetics Kurfürstendamm 199. Available datasets from the three study locations
were identified and reference curves were generated using the LMS method. Measured
values were correlated with age of gestation, and a cubic model and Box-Cox power
transformation (L), the median (M) and the coefficient of variation (S) were used
to smooth the curves.
Results 103 720 Doppler examinations of the UA carried out in singleton pregnancies from
the 11th week of gestation (10 + 1 GW) were analyzed. The mean pulsatility index (Mean
PI) showed a continuous decline over the course of pregnancy, dropping to a plateau
of around 0.84 between the 23rd and 27th GW, after which it decreased again.
Conclusion Age of gestation, placental position, position of pulsed Doppler gates and branching
of the UA can all change the flow pattern. The mean pulsatility index (Mean PI) showed
a continuous decrease over time. There were significant differences between our data
and alternative reference curves. A system of classifying Doppler studies and a reference
curve adapted to the current technology are urgently required to differentiate better
between physiological and pathological findings.
Key words
preeclampsia - placenta - growth retardation - ultrasound - uterine artery - Doppler
